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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title><![CDATA[夜阳's Blog]]></title>
<subtitle><![CDATA[记录点滴 | 仰望星空，脚踏实地]]></subtitle>
<link href="/atom.xml" rel="self"/>
<link href="http://jakezy.com//"/>
<updated>2015-09-05T00:20:44.809Z</updated>
<id>http://jakezy.com//</id>
<author>
<name><![CDATA[Jake Z]]></name>
<email><![CDATA[zyseap@gmail.com]]></email>
</author>
<generator uri="http://hexo.io/">Hexo</generator>
<entry>
<title><![CDATA[Ubuntu环境配置]]></title>
<link href="http://jakezy.com/2015/09/05/Ubuntu%E7%8E%AF%E5%A2%83%E9%85%8D%E7%BD%AE/"/>
<id>http://jakezy.com/2015/09/05/Ubuntu环境配置/</id>
<published>2015-09-05T00:17:33.000Z</published>
<updated>2015-09-05T00:20:44.809Z</updated>
<content type="html"><![CDATA[<p>待完成…（等校招季过去了再来补全）</p>
]]></content>
<summary type="html">
<![CDATA[<p>待完成…（等校招季过去了再来补全）</p>
]]>
</summary>
<category term="Linux" scheme="http://jakezy.com/tags/Linux/"/>
<category term="Ubuntu" scheme="http://jakezy.com/tags/Ubuntu/"/>
<category term="life" scheme="http://jakezy.com/tags/life/"/>
<category term="Ubuntu" scheme="http://jakezy.com/categories/Ubuntu/"/>
</entry>
<entry>
<title><![CDATA[九章算法阶梯训练]]></title>
<link href="http://jakezy.com/2015/08/26/%E4%B9%9D%E7%AB%A0%E7%AE%97%E6%B3%95%E9%98%B6%E6%A2%AF%E8%AE%AD%E7%BB%83/"/>
<id>http://jakezy.com/2015/08/26/九章算法阶梯训练/</id>
<published>2015-08-25T21:12:38.000Z</published>
<updated>2015-08-25T21:15:36.657Z</updated>
<content type="html"><![CDATA[<p>这几天按照<a href="http://www.lintcode.com/en/ladder/" target="_blank" rel="external">九章算法阶梯训练</a>开始刷题，建了个Gitbook，把相关的Leetcode代码都转移到Gitbook上了<br>之后会写一篇Gitbook发布到Github Pages的教程</p>
<p>Gitbook：<a href="http://jakezy.com/Nine-Chapters-Ladder/">九章算法阶梯训练（Nine Chapters / Ladder）</a></p>
]]></content>
<summary type="html">
<![CDATA[<p>这几天按照<a href="http://www.lintcode.com/en/ladder/" target="_blank" rel="external">九章算法阶梯训练</a>开始刷题，建了个Gitbook，把相关的Leetcode代码都转移到Gitbook上了<]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 16 Binary Search & Sorted Array]]></title>
<link href="http://jakezy.com/2015/08/25/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-16/"/>
<id>http://jakezy.com/2015/08/25/Leetcode刷题记录-16/</id>
<published>2015-08-25T02:11:30.000Z</published>
<updated>2015-08-25T15:36:21.915Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/merge-sorted-array/" target="_blank" rel="external">Merge Sorted Array</a></li>
<li><a href="https://leetcode.com/problems/search-insert-position/" target="_blank" rel="external">Search Insert Position</a></li>
<li><a href="http://www.lintcode.com/en/problem/recover-rotated-sorted-array/" target="_blank" rel="external">Recover Rotated Sorted Array</a></li>
<li><a href="http://www.lintcode.com/en/problem/binary-search/" target="_blank" rel="external">Binary Search</a></li>
<li><a href="https://leetcode.com/problems/find-peak-element/" target="_blank" rel="external">Find Peak Element</a></li>
<li><a href="http://www.lintcode.com/en/problem/first-bad-version/" target="_blank" rel="external">First Bad Version</a></li>
<li><a href="https://leetcode.com/problems/search-in-rotated-sorted-array/" target="_blank" rel="external">Search in Rotated Sorted Array</a></li>
<li><a href="https://leetcode.com/problems/search-for-a-range/" target="_blank" rel="external">Search for a Range</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Merge_Sorted_Array"><a href="https://leetcode.com/problems/merge-sorted-array/" target="_blank" rel="external">Merge Sorted Array</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">merge</span><span class="params">(<span class="keyword">int</span>[] nums1, <span class="keyword">int</span> m, <span class="keyword">int</span>[] nums2, <span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> i = m - <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> j = n - <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> k = m + n - <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">while</span> (k >= <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">if</span> (j < <span class="number">0</span> || (i >= <span class="number">0</span> && nums1[i] > nums2[j])) {</span><br><span class="line"> nums1[k--] = nums1[i--];</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> nums1[k--] = nums2[j--];</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Search_Insert_Position"><a href="https://leetcode.com/problems/search-insert-position/" target="_blank" rel="external">Search Insert Position</a></h2><p>思路：<br>二分查找，注意边界条件</p>
<ol>
<li>循环跳出条件：low <= high</li>
<li>退出条件：mid / mid + 1</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">searchInsert</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (nums.length == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">0</span>, high = nums.length - <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> mid = low + (high - low) / <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> mid = low + (high - low) / <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] < target) {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (nums[mid] > target) {</span><br><span class="line"> high = mid - <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> mid;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] < target) {</span><br><span class="line"> <span class="keyword">return</span> mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> mid;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Recover_Rotated_Sorted_Array"><a href="http://www.lintcode.com/en/problem/recover-rotated-sorted-array/" target="_blank" rel="external">Recover Rotated Sorted Array</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * <span class="doctag">@param</span> nums: The rotated sorted array</span><br><span class="line"> * <span class="doctag">@return</span>: void</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">recoverRotatedSortedArray</span><span class="params">(ArrayList<Integer> nums)</span> </span>{</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < nums.size(); i++) {</span><br><span class="line"> <span class="keyword">if</span> (nums.get(i) < nums.get(i - <span class="number">1</span>)) {</span><br><span class="line"> reverse(nums, <span class="number">0</span>, i - <span class="number">1</span>);</span><br><span class="line"> reverse(nums, i, nums.size() - <span class="number">1</span>);</span><br><span class="line"> reverse(nums, <span class="number">0</span>, nums.size() - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">reverse</span><span class="params">(List<Integer> nums, <span class="keyword">int</span> start, <span class="keyword">int</span> end)</span> </span>{</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = start, j = end; i < j; i++, j--) {</span><br><span class="line"> <span class="keyword">int</span> temp = nums.get(i);</span><br><span class="line"> nums.set(i, nums.get(j));</span><br><span class="line"> nums.set(j, temp);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Binary_Search"><a href="http://www.lintcode.com/en/problem/binary-search/" target="_blank" rel="external">Binary Search</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * <span class="doctag">@param</span> nums: The integer array.</span><br><span class="line"> * <span class="doctag">@param</span> target: Target to find.</span><br><span class="line"> * <span class="doctag">@return</span>: The first position of target. Position starts from 0.</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">binarySearch</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (nums == <span class="keyword">null</span> || nums.length == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">0</span>, high = nums.length - <span class="number">1</span>, mid;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> mid = low + (high - low) / <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] < target) {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (nums[mid] > target) {</span><br><span class="line"> high = mid - <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">while</span> (mid > <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] == nums[mid - <span class="number">1</span>]) {</span><br><span class="line"> mid--;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> mid;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Find_Peak_Element"><a href="https://leetcode.com/problems/find-peak-element/" target="_blank" rel="external">Find Peak Element</a></h2><p>思路：<br>二分查找<br>循环结束条件：low == high<br>始终拿mid和mid+1比较：<br>若升序(nums[mid] < nums[mid + 1])，则峰值在mid+1右侧，low = mid + 1<br>若降序(nums[mid] >= nums[mid + 1]), 则峰值在mid左侧，high = mid</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">findPeakElement</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">0</span>, high = nums.length - <span class="number">1</span>, mid;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> <span class="keyword">if</span> (low == high) {</span><br><span class="line"> <span class="keyword">return</span> low;</span><br><span class="line"> }</span><br><span class="line"> mid = low + (high - low) / <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] < nums[mid + <span class="number">1</span>]) {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> high = mid;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="First_Bad_Version"><a href="http://www.lintcode.com/en/problem/first-bad-version/" target="_blank" rel="external">First Bad Version</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * public class VersionControl {</span><br><span class="line"> * public static boolean isBadVersion(int k);</span><br><span class="line"> * }</span><br><span class="line"> * you can use VersionControl.isBadVersion(k) to judge whether </span><br><span class="line"> * the kth code version is bad or not.</span><br><span class="line">*/</span></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * <span class="doctag">@param</span> n: An integers.</span><br><span class="line"> * <span class="doctag">@return</span>: An integer which is the first bad version.</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">findFirstBadVersion</span><span class="params">(<span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">1</span>, high = n, mid;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> <span class="keyword">if</span> (low == high) {</span><br><span class="line"> <span class="keyword">return</span> high;</span><br><span class="line"> }</span><br><span class="line"> mid = low + (high - low) / <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">if</span> (VersionControl.isBadVersion(mid)) {</span><br><span class="line"> high = mid;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Search_in_Rotated_Sorted_Array"><a href="https://leetcode.com/problems/search-in-rotated-sorted-array/" target="_blank" rel="external">Search in Rotated Sorted Array</a></h2><p>思路：<br>参考<a href="http://fisherlei.blogspot.com/2013/01/leetcode-search-in-rotated-sorted-array.html" target="_blank" rel="external">水中的鱼</a><br><img src="http://3.bp.blogspot.com/-ovV6zYeEdZg/U_ke6coEoAI/AAAAAAAAIc4/lmb1A9FsjgQ/s1600/Picture123.png" alt=""></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">search</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">0</span>, high = nums.length - <span class="number">1</span>, mid;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> mid = low + ((high - low) >> <span class="number">1</span>);</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] == target) {</span><br><span class="line"> <span class="keyword">return</span> mid;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (nums[low] <= nums[mid]) {</span><br><span class="line"> <span class="keyword">if</span> (nums[low] <= target && target < nums[mid]) {</span><br><span class="line"> high = mid - <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">if</span> (nums[mid] < target && target <= nums[high]) {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> high = mid - <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Search_for_a_Range"><a href="https://leetcode.com/problems/search-for-a-range/" target="_blank" rel="external">Search for a Range</a></h2><p>思路：<br>二分查找位置<br>向左走找到最左<br>向右走找到最右</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> <span class="keyword">int</span>[] searchRange(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target) {</span><br><span class="line"> <span class="keyword">int</span>[] result = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">2</span>];</span><br><span class="line"> <span class="keyword">int</span> index = binarySearch(nums, target);</span><br><span class="line"> <span class="keyword">if</span> (index == -<span class="number">1</span>) {</span><br><span class="line"> result[<span class="number">0</span>] = -<span class="number">1</span>;</span><br><span class="line"> result[<span class="number">1</span>] = -<span class="number">1</span>;</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> left = index;</span><br><span class="line"> <span class="keyword">while</span> (left > <span class="number">0</span> && nums[left] == nums[left - <span class="number">1</span>]) {</span><br><span class="line"> left--;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> right = index;</span><br><span class="line"> <span class="keyword">while</span> (right < nums.length - <span class="number">1</span> && nums[right] == nums[right + <span class="number">1</span>]) {</span><br><span class="line"> right++;</span><br><span class="line"> }</span><br><span class="line"> result[<span class="number">0</span>] = left;</span><br><span class="line"> result[<span class="number">1</span>] = right;</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">int</span> <span class="title">binarySearch</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> target)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> low = <span class="number">0</span>, high = nums.length - <span class="number">1</span>, mid;</span><br><span class="line"> <span class="keyword">while</span> (low <= high) {</span><br><span class="line"> mid = low + ((high - low) >> <span class="number">1</span>);</span><br><span class="line"> <span class="keyword">if</span> (target > nums[mid]) {</span><br><span class="line"> low = mid + <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (target < nums[mid]) {</span><br><span class="line"> high = mid - <span class="number">1</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">return</span> mid;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/merge-sorted-array/">Merge Sorted Array</a></li>
<li><a href="https://leetcode.com/problems/search-insert-position/">Search Insert Position</a></li>
<li><a href="http://www.lintcode.com/en/problem/recover-rotated-sorted-array/">Recover Rotated Sorted Array</a></li>
<li><a href="http://www.lintcode.com/en/problem/binary-search/">Binary Search</a></li>
<li><a href="https://leetcode.com/problems/find-peak-element/">Find Peak Element</a></li>
<li><a href="http://www.lintcode.com/en/problem/first-bad-version/">First Bad Version</a></li>
<li><a href="https://leetcode.com/problems/search-in-rotated-sorted-array/">Search in Rotated Sorted Array</a></li>
<li><a href="https://leetcode.com/problems/search-for-a-range/">Search for a Range</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 15 strStr & Coding Style]]></title>
<link href="http://jakezy.com/2015/08/24/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-15/"/>
<id>http://jakezy.com/2015/08/24/Leetcode刷题记录-15/</id>
<published>2015-08-24T09:45:30.000Z</published>
<updated>2015-08-25T10:09:28.886Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/implement-strstr/" target="_blank" rel="external">Implement strStr()</a></li>
<li><a href="https://leetcode.com/problems/subsets/" target="_blank" rel="external">Subsets</a></li>
<li><a href="https://leetcode.com/problems/subsets-ii/" target="_blank" rel="external">Subsets II</a></li>
<li><a href="https://leetcode.com/problems/permutations/" target="_blank" rel="external">Permutations</a></li>
<li><a href="https://leetcode.com/problems/permutations-ii/" target="_blank" rel="external">Permutations II</a></li>
<li><a href="https://leetcode.com/problems/permutation-sequence/" target="_blank" rel="external">Permutation Sequence</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Implement_strStr()"><a href="https://leetcode.com/problems/implement-strstr/" target="_blank" rel="external">Implement strStr()</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">strStr</span><span class="params">(String haystack, String needle)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (haystack == <span class="keyword">null</span> || needle == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> i, j;</span><br><span class="line"> <span class="keyword">for</span> (i = <span class="number">0</span>; i < haystack.length() - needle.length() + <span class="number">1</span>; i++) {</span><br><span class="line"> <span class="keyword">for</span> (j = <span class="number">0</span>; j < needle.length(); j++) {</span><br><span class="line"> <span class="keyword">if</span> (haystack.charAt(i + j) != needle.charAt(j))</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (j == needle.length()) {</span><br><span class="line"> <span class="keyword">return</span> i;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Subsets"><a href="https://leetcode.com/problems/subsets/" target="_blank" rel="external">Subsets</a></h2><p>思路：<br>递归构造</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> List<List<Integer>> subsets(<span class="keyword">int</span>[] nums) {</span><br><span class="line"> List<List<Integer>> result = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> List<Integer> res = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> Arrays.sort(nums);</span><br><span class="line"> subsetsHelper(result, res, nums, <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">subsetsHelper</span><span class="params">(List<List<Integer>> result, List<Integer> res, <span class="keyword">int</span>[] nums, <span class="keyword">int</span> pos)</span> </span>{</span><br><span class="line"> result.add(<span class="keyword">new</span> ArrayList<>(res));</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = pos; i < nums.length; i++) {</span><br><span class="line"> res.add(nums[i]);</span><br><span class="line"> subsetsHelper(result, res, nums, i + <span class="number">1</span>);</span><br><span class="line"> res.remove(res.size() - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Subsets_II"><a href="https://leetcode.com/problems/subsets-ii/" target="_blank" rel="external">Subsets II</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> List<List<Integer>> subsetsWithDup(<span class="keyword">int</span>[] nums) {</span><br><span class="line"> List<List<Integer>> result = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> List<Integer> res = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> Arrays.sort(nums);</span><br><span class="line"> subsetsHelper(result, res, nums, <span class="number">0</span>);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">subsetsHelper</span><span class="params">(List<List<Integer>> result, List<Integer> res, <span class="keyword">int</span>[] nums, <span class="keyword">int</span> pos)</span> </span>{</span><br><span class="line"> result.add(<span class="keyword">new</span> ArrayList<>(res));</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = pos; i < nums.length; i++) {</span><br><span class="line"> <span class="keyword">if</span> (i != pos && nums[i] == nums[i - <span class="number">1</span>]) {</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> res.add(nums[i]);</span><br><span class="line"> subsetsHelper(result, res, nums, i + <span class="number">1</span>);</span><br><span class="line"> res.remove(res.size() - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Permutations"><a href="https://leetcode.com/problems/permutations/" target="_blank" rel="external">Permutations</a></h2><p>思路：<br>visited[]记录该位置是否访问过</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> List<List<Integer>> permute(<span class="keyword">int</span>[] nums) {</span><br><span class="line"> List<List<Integer>> result = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> <span class="keyword">if</span> (nums == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">boolean</span>[] visited = <span class="keyword">new</span> <span class="keyword">boolean</span>[nums.length];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < visited.length; i++) {</span><br><span class="line"> visited[i] = <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> List<Integer> res = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> permuteHelper(result, res, nums, visited);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">permuteHelper</span><span class="params">(List<List<Integer>> result, List<Integer> res, <span class="keyword">int</span>[] nums, <span class="keyword">boolean</span>[] visited)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (res.size() == nums.length) {</span><br><span class="line"> result.add(<span class="keyword">new</span> ArrayList<>(res));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < nums.length; i++) {</span><br><span class="line"> <span class="keyword">if</span> (visited[i]) {</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> res.add(nums[i]);</span><br><span class="line"> visited[i] = <span class="keyword">true</span>;</span><br><span class="line"> permuteHelper(result, res, nums, visited);</span><br><span class="line"> res.remove(res.size() - <span class="number">1</span>);</span><br><span class="line"> visited[i] = <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Permutations_II"><a href="https://leetcode.com/problems/permutations-ii/" target="_blank" rel="external">Permutations II</a></h2><p>思路：<br>注意循环跳过条件</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">public</span> List<List<Integer>> permuteUnique(<span class="keyword">int</span>[] nums) {</span><br><span class="line"> List<List<Integer>> result = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> <span class="keyword">if</span> (nums == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> Arrays.sort(nums);</span><br><span class="line"> List<Integer> res = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> <span class="keyword">boolean</span>[] visited = <span class="keyword">new</span> <span class="keyword">boolean</span>[nums.length];</span><br><span class="line"> permuteUniqueHelper(result, res, nums, visited);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">permuteUniqueHelper</span><span class="params">(List<List<Integer>> result, List<Integer> res, <span class="keyword">int</span>[] nums, <span class="keyword">boolean</span>[] visited)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (res.size() == nums.length) {</span><br><span class="line"> result.add(<span class="keyword">new</span> ArrayList<>(res));</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < nums.length; i++) {</span><br><span class="line"> <span class="keyword">if</span> (visited[i] || (i > <span class="number">0</span> && nums[i] == nums[i - <span class="number">1</span>] && !visited[i - <span class="number">1</span>])) {</span><br><span class="line"> <span class="keyword">continue</span>;</span><br><span class="line"> }</span><br><span class="line"> res.add(nums[i]);</span><br><span class="line"> visited[i] = <span class="keyword">true</span>;</span><br><span class="line"> permuteUniqueHelper(result, res, nums, visited);</span><br><span class="line"> res.remove(res.size() - <span class="number">1</span>);</span><br><span class="line"> visited[i] = <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Permutation_Sequence"><a href="https://leetcode.com/problems/permutation-sequence/" target="_blank" rel="external">Permutation Sequence</a></h2><p>思路一：<br>递归构造所有排列，返回第k个</p>
<p>思路二：<br>找数学规律<br>假设有$n$个元素，第$k$个permutation是$a_1a_2\ldots a_n$<br>对于$a_1$开头的排列，$a_2…a_n$共$n-1$个元素，有$(n-1)!$种排列<br>令$i = k / (n-1)!$，表示第$k$个permutation在第$i$组，$a_1 = k / (n-1)!$<br>令$k’ = k \% (n-1)!$，表示第$k$个permutation在第$i$组的$k’$位置<br>则有：</p>
<blockquote>
<p>$k_1 = k$<br>$a_1 = k_1 / (n-1)!$<br>$k_2 = k_1 \% (n-1)!$<br>$a_2 = k_2 / (n-2)!$<br>$\ldots$</p>
</blockquote>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">getPermutation</span><span class="params">(<span class="keyword">int</span> n, <span class="keyword">int</span> k)</span> </span>{</span><br><span class="line"> StringBuilder result = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"> List<Integer> nums = <span class="keyword">new</span> ArrayList<>();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i <= n; i++) {</span><br><span class="line"> nums.add(i);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> k--;</span><br><span class="line"> <span class="keyword">int</span> factorial = <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">2</span>; i <= n; i++) {</span><br><span class="line"> factorial *= i;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < n; i++) {</span><br><span class="line"> factorial /= n - i; <span class="comment">// factorial = (n-i-1)!</span></span><br><span class="line"> <span class="keyword">int</span> index = k / factorial;</span><br><span class="line"> result.append(nums.get(index));</span><br><span class="line"> nums.remove(index);</span><br><span class="line"> k %= factorial;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> result.toString();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/implement-strstr/">Implement strStr()</a></li>
<li><a href="https://leetcode.com/problems/subsets/">Subsets</a></li>
<li><a href="https://leetcode.com/problems/subsets-ii/">Subsets II</a></li>
<li><a href="https://leetcode.com/problems/permutations/">Permutations</a></li>
<li><a href="https://leetcode.com/problems/permutations-ii/">Permutations II</a></li>
<li><a href="https://leetcode.com/problems/permutation-sequence/">Permutation Sequence</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[近期阅读]]></title>
<link href="http://jakezy.com/2015/08/24/%E8%BF%91%E6%9C%9F%E9%98%85%E8%AF%BB/"/>
<id>http://jakezy.com/2015/08/24/近期阅读/</id>
<published>2015-08-24T02:52:38.000Z</published>
<updated>2015-08-24T05:25:30.668Z</updated>
<content type="html"><![CDATA[<p>近期阅读<br><a id="more"></a></p>
<ul>
<li><a href="http://blog.eood.cn/rate-limiting" target="_blank" rel="external">架构必备：Rate limiting 的作用和常见方式</a></li>
<li><a href="http://vinoyang.com/2015/08/17/redis-practice-of-preempting-dorm/" target="_blank" rel="external">redis在学生抢房应用中的实践总结</a></li>
<li><a href="http://outofmemory.cn/mysql/mysql-index-arithmetic" target="_blank" rel="external"><strong>MySQL索引背后的数据结构及算法原理</strong></a></li>
<li><a href="http://blog.csdn.net/duqi_2009/article/details/47752169" target="_blank" rel="external">Spring+Velocity+Mybatis入门（step by step）</a></li>
</ul>
]]></content>
<summary type="html">
<![CDATA[<p>近期阅读<br>]]>
</summary>
<category term="life" scheme="http://jakezy.com/tags/life/"/>
<category term="reading" scheme="http://jakezy.com/tags/reading/"/>
<category term="生活记录" scheme="http://jakezy.com/categories/%E7%94%9F%E6%B4%BB%E8%AE%B0%E5%BD%95/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 14]]></title>
<link href="http://jakezy.com/2015/08/08/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-14/"/>
<id>http://jakezy.com/2015/08/08/Leetcode刷题记录-14/</id>
<published>2015-08-08T09:11:58.000Z</published>
<updated>2015-08-24T09:44:19.551Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/excel-sheet-column-title/" target="_blank" rel="external">Excel Sheet Column Title</a></li>
<li><a href="https://leetcode.com/problems/excel-sheet-column-number/" target="_blank" rel="external">Excel Sheet Column Number</a></li>
<li><a href="https://leetcode.com/problems/basic-calculator-ii/" target="_blank" rel="external">Basic Calculator II</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Excel_Sheet_Column_Title"><a href="https://leetcode.com/problems/excel-sheet-column-title/" target="_blank" rel="external">Excel Sheet Column Title</a></h2><figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> Solution {</span><br><span class="line"> <span class="function"><span class="keyword">public</span> String <span class="title">convertToTitle</span><span class="params">(<span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> StringBuilder sb = <span class="keyword">new</span> StringBuilder();</span><br><span class="line"> <span class="keyword">while</span> (n > <span class="number">0</span>) {</span><br><span class="line"> n--;</span><br><span class="line"> <span class="keyword">char</span> ch = (<span class="keyword">char</span>) (n % <span class="number">26</span> + <span class="string">'A'</span>);</span><br><span class="line"> sb.append(ch);</span><br><span class="line"> n = n / <span class="number">26</span>;</span><br><span class="line"> }</span><br><span class="line"> sb.reverse();</span><br><span class="line"> <span class="keyword">return</span> sb.toString();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Excel_Sheet_Column_Number"><a href="https://leetcode.com/problems/excel-sheet-column-number/" target="_blank" rel="external">Excel Sheet Column Number</a></h2><p>思路：<br>26进制转10进制<br>$ABCD_{26} = 1\times26^3 + 2\times26^2 + 3\times26^1 + 4\times26^0$</p>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> Solution {</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">titleToNumber</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> num = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < s.length(); i++) {</span><br><span class="line"> <span class="keyword">char</span> ch = s.charAt(i);</span><br><span class="line"> <span class="keyword">int</span> n = ch - <span class="string">'A'</span> + <span class="number">1</span>;</span><br><span class="line"> num += Math.<span class="built_in">pow</span>(<span class="number">26</span>, s.length() - i - <span class="number">1</span>) * n;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> num;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Basic_Calculator_II"><a href="https://leetcode.com/problems/basic-calculator-ii/" target="_blank" rel="external">Basic Calculator II</a></h2><p>思路一：<br>parseMulDiv：计算下一个操作数（这里的操作数指乘除法计算完后的操作数）<br>初始时先使用parseMulDiv计算一个操作数赋给result，直到下一个运算符不是乘除<br>保存下一个运算符（+/-），使用parseMulDiv计算下一个操作数，加减运算后赋给result<br>继续查找下一个运算符和操作数，直到字符串末尾</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">int</span> cur = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">calculate</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> result = <span class="number">0</span>;</span><br><span class="line"> s = s.replace(<span class="string">" "</span>, <span class="string">""</span>);</span><br><span class="line"> result = parseMulDiv(s);</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> c = s.charAt(cur);</span><br><span class="line"> cur++;</span><br><span class="line"> <span class="keyword">int</span> b = parseMulDiv(s);</span><br><span class="line"> <span class="keyword">if</span> (c == <span class="string">'+'</span>) {</span><br><span class="line"> result += b;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (c == <span class="string">'-'</span>) {</span><br><span class="line"> result -= b;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">int</span> <span class="title">parseMulDiv</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> num = parseNum(s);</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> c = s.charAt(cur);</span><br><span class="line"> <span class="keyword">if</span> (c != <span class="string">'*'</span> && c != <span class="string">'/'</span>) {</span><br><span class="line"> <span class="keyword">return</span> num;</span><br><span class="line"> }</span><br><span class="line"> cur++;</span><br><span class="line"> <span class="keyword">int</span> nextNum = parseNum(s);</span><br><span class="line"> <span class="keyword">if</span> (c == <span class="string">'*'</span>) {</span><br><span class="line"> num *= nextNum;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (c == <span class="string">'/'</span>) {</span><br><span class="line"> num /= nextNum;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> num;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">int</span> <span class="title">parseNum</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> c = s.charAt(cur);</span><br><span class="line"> <span class="keyword">if</span> (c < <span class="string">'0'</span> || c > <span class="string">'9'</span>) {</span><br><span class="line"> <span class="keyword">return</span> n;</span><br><span class="line"> }</span><br><span class="line"> n = n * <span class="number">10</span> + c - <span class="string">'0'</span>;</span><br><span class="line"> cur++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> n;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p>思路二：<br>num记录当前待参与运算的运算数，lastOpt记录上一个加减运算符，result记录表达式的值<br>若当前运算符为乘除法，则对num与下一个运算数nextNum执行乘除运算，赋值给num<br>若当前运算符为加减法，则对result与num执行lastOpt（加减）运算，赋值给result，并更新lastOpt<br>这种方法需要在表达式前后各加一个“+”<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"></span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">int</span> cur = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">calculate</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> s = s.replace(<span class="string">" "</span>, <span class="string">""</span>);</span><br><span class="line"> s = s + <span class="string">"+"</span>;</span><br><span class="line"> <span class="keyword">int</span> result = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">char</span> lastOpt = <span class="string">'+'</span>;</span><br><span class="line"> <span class="keyword">int</span> num = parseNum(s);</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> opt = parseOpt(s);</span><br><span class="line"> <span class="keyword">if</span> (opt == <span class="string">'+'</span> || opt == <span class="string">'-'</span>) {</span><br><span class="line"> <span class="keyword">if</span> (lastOpt == <span class="string">'+'</span>)</span><br><span class="line"> result += num;</span><br><span class="line"> <span class="keyword">else</span> <span class="keyword">if</span> (lastOpt == <span class="string">'-'</span>)</span><br><span class="line"> result -= num;</span><br><span class="line"> lastOpt = opt;</span><br><span class="line"> num = parseNum(s);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">int</span> nextNum = parseNum(s);</span><br><span class="line"> <span class="keyword">if</span> (opt == <span class="string">'*'</span>)</span><br><span class="line"> num *= nextNum;</span><br><span class="line"> <span class="keyword">else</span> <span class="keyword">if</span> (opt == <span class="string">'/'</span>)</span><br><span class="line"> num /= nextNum;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">char</span> <span class="title">parseOpt</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> c = s.charAt(cur);</span><br><span class="line"> cur++;</span><br><span class="line"> <span class="keyword">return</span> c;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">int</span> <span class="title">parseNum</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (cur < s.length()) {</span><br><span class="line"> <span class="keyword">char</span> c = s.charAt(cur);</span><br><span class="line"> <span class="keyword">if</span> (c < <span class="string">'0'</span> || c > <span class="string">'9'</span>) {</span><br><span class="line"> <span class="keyword">return</span> n;</span><br><span class="line"> }</span><br><span class="line"> n = n * <span class="number">10</span> + c - <span class="string">'0'</span>;</span><br><span class="line"> cur++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> n;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p>
]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/excel-sheet-column-title/">Excel Sheet Column Title</a></li>
<li><a href="https://leetcode.com/problems/excel-sheet-column-number/">Excel Sheet Column Number</a></li>
<li><a href="https://leetcode.com/problems/basic-calculator-ii/">Basic Calculator II</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[AtomicInteger]]></title>
<link href="http://jakezy.com/2015/08/08/AtomicInteger/"/>
<id>http://jakezy.com/2015/08/08/AtomicInteger/</id>
<published>2015-08-08T04:01:02.000Z</published>
<updated>2015-08-08T04:53:14.920Z</updated>
<content type="html"><![CDATA[<h3 id="实现方式">实现方式</h3><p>AtomicInteger是一个支持原子操作的Integer类<br><a id="more"></a></p>
<p>用AtomicInteger实现的顺序id获取：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> AtomicInteger counter = <span class="keyword">new</span> AtomicInteger();</span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">int</span> <span class="title">getNextId</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> counter.incrementAndGet();</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p>
<h4 id="incrementAndGet()">incrementAndGet()</h4><p>简化后的相关代码：<br><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">AtomicInteger</span> <span class="keyword">extends</span> <span class="title">Number</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">volatile</span> <span class="keyword">int</span> value;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">int</span> <span class="title">get</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">return</span> value;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * Atomically increments by one the current value.</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@return</span> the updated value</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">int</span> <span class="title">incrementAndGet</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="comment">// 无限循环直到value设置成功</span></span><br><span class="line"> <span class="keyword">for</span> (;;) {</span><br><span class="line"> <span class="keyword">int</span> current = get();</span><br><span class="line"> <span class="keyword">int</span> next = current + <span class="number">1</span>;</span><br><span class="line"> <span class="comment">// 前两步非线程安全，因此不能直接返回next</span></span><br><span class="line"> <span class="comment">// 因为此时可能会有其他线程已经对current进行了更改，所以要调用compareAndSet判断</span></span><br><span class="line"> <span class="keyword">if</span> (compareAndSet(current, next))</span><br><span class="line"> <span class="keyword">return</span> next;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * Atomically sets the value to the given updated value</span><br><span class="line"> * if the current value {<span class="doctag">@code</span> ==} the expected value.</span><br><span class="line"> *</span><br><span class="line"> * <span class="doctag">@param</span> expect the expected value</span><br><span class="line"> * <span class="doctag">@param</span> update the new value</span><br><span class="line"> * <span class="doctag">@return</span> true if successful. False return indicates that</span><br><span class="line"> * the actual value was not equal to the expected value.</span><br><span class="line"> */</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">boolean</span> <span class="title">compareAndSet</span><span class="params">(<span class="keyword">int</span> expect, <span class="keyword">int</span> update)</span> </span>{</span><br><span class="line"> <span class="comment">// CAS有3个操作数：内存值value，要跟内存值做比较的值expect和新值update</span></span><br><span class="line"> <span class="comment">// 若value==expect，则令value=update，返回true；否则，返回false</span></span><br><span class="line"> <span class="keyword">return</span> unsafe.compareAndSwapInt(<span class="keyword">this</span>, valueOffset, expect, update);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure></p>
<blockquote>
<p>不使用compareAndSet可能出现的异常：</p>
<ol>
<li>A线程执行get()操作，获取current值（假设为1）</li>
<li>B线程执行get()操作，获取current值（为1）</li>
<li>B线程执行next = current + 1操作，next = 2</li>
<li>A线程执行next = current + 1操作，next = 2</li>
</ol>
</blockquote>
<p>compareAndSet调用native方法compareAndSwapInt，它基于CAS原语实现，由CPU比较内存位置上的值是否为当前值，若是则将其设置为next，否则返回false<br>基于CAS的操作可认为是无阻塞的，且CAS原语性能会好于同步锁</p>
<h5 id="基于原子类的CAS操作自主实现无阻塞操作">基于原子类的CAS操作自主实现无阻塞操作</h5><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/*</span><br><span class="line"> * CAS操作判断当前方法是否已经初始化</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">AtomicBooleanTest</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">int</span> flag = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">private</span> <span class="keyword">static</span> AtomicBoolean inited = <span class="keyword">new</span> AtomicBoolean();</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">init</span><span class="params">()</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (!inited.compareAndSet(<span class="keyword">false</span>, <span class="keyword">true</span>)) {</span><br><span class="line"> System.out.println(<span class="string">"已初始化："</span> + flag);</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 初始化操作</span></span><br><span class="line"> System.out.println(<span class="string">"未初始化："</span> + flag);</span><br><span class="line"> flag++;</span><br><span class="line"> System.out.println(<span class="string">"初始化完毕："</span> + flag);</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>{</span><br><span class="line"> init();</span><br><span class="line"> System.out.println(<span class="string">"-----"</span>);</span><br><span class="line"> init();</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<h3 id="实现方式">实现方式</h3><p>AtomicInteger是一个支持原子操作的Integer类<br>]]>
</summary>
<category term="JDK" scheme="http://jakezy.com/tags/JDK/"/>
<category term="Java" scheme="http://jakezy.com/categories/Java/"/>
</entry>
<entry>
<title><![CDATA[java.util.ConcurrentModificationException出现原因及解决办法]]></title>
<link href="http://jakezy.com/2015/08/06/java.util.ConcurrentModificationException%E5%87%BA%E7%8E%B0%E5%8E%9F%E5%9B%A0%E5%8F%8A%E8%A7%A3%E5%86%B3%E5%8A%9E%E6%B3%95/"/>
<id>http://jakezy.com/2015/08/06/java.util.ConcurrentModificationException出现原因及解决办法/</id>
<published>2015-08-06T14:06:21.000Z</published>
<updated>2015-08-06T14:08:21.925Z</updated>
<content type="html"><![CDATA[<p>待补充</p>
]]></content>
<summary type="html">
<![CDATA[<p>待补充</p>
]]>
</summary>
<category term="问题记录" scheme="http://jakezy.com/tags/%E9%97%AE%E9%A2%98%E8%AE%B0%E5%BD%95/"/>
<category term="Java" scheme="http://jakezy.com/categories/Java/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 13]]></title>
<link href="http://jakezy.com/2015/08/06/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-13/"/>
<id>http://jakezy.com/2015/08/06/Leetcode刷题记录-13/</id>
<published>2015-08-06T14:01:33.000Z</published>
<updated>2015-08-06T14:14:01.690Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/majority-element/" target="_blank" rel="external">Majority Element</a></li>
<li><a href="https://leetcode.com/problems/majority-element-ii/" target="_blank" rel="external">Majority Element II</a></li>
<li><a href="http://www.lintcode.com/en/problem/majority-number-iii/" target="_blank" rel="external">Majority Number III</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Majority_Element"><a href="https://leetcode.com/problems/majority-element/" target="_blank" rel="external">Majority Element</a></h2><p>思路：<br>多数投票算法：</p>
<ol>
<li>若count==0，则将result设为数组当前元素num，count++</li>
<li>若result和现在数组元素num相同，则count++，否则count–</li>
<li>重复上述两步，直到扫描完数组</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">majorityElement</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> result = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> num : nums) {</span><br><span class="line"> <span class="keyword">if</span> (n == <span class="number">0</span>) {</span><br><span class="line"> result = num;</span><br><span class="line"> n++;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">if</span> (result == num) {</span><br><span class="line"> n++;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> n--;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Majority_Element_II"><a href="https://leetcode.com/problems/majority-element-ii/" target="_blank" rel="external">Majority Element II</a></h2><p>思路：<br>出现次数大于n/3的数最多两个，最少一个也没有<br>同样利用多数投票算法，但此时有两个候选元素<br>注意两个候选元素相同的情况，最后要再重新统计一遍两个候选元素的出现次数</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> List<Integer> <span class="title">majorityElement</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> List<Integer> result = <span class="keyword">new</span> ArrayList<Integer>(<span class="number">2</span>);</span><br><span class="line"> <span class="keyword">if</span> (nums.length == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span>[] number = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">2</span>];</span><br><span class="line"> <span class="keyword">int</span>[] count = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">2</span>];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> num : nums) {</span><br><span class="line"> <span class="keyword">if</span> (count[<span class="number">0</span>] == <span class="number">0</span>) {</span><br><span class="line"> number[<span class="number">0</span>] = num;</span><br><span class="line"> count[<span class="number">0</span>]++;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (count[<span class="number">1</span>] == <span class="number">0</span> && number[<span class="number">0</span>] != num) {</span><br><span class="line"> number[<span class="number">1</span>] = num;</span><br><span class="line"> count[<span class="number">1</span>]++;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> <span class="keyword">if</span> (num == number[<span class="number">0</span>]) {</span><br><span class="line"> count[<span class="number">0</span>]++;</span><br><span class="line"> } <span class="keyword">else</span> <span class="keyword">if</span> (num == number[<span class="number">1</span>]) {</span><br><span class="line"> count[<span class="number">1</span>]++;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> count[<span class="number">0</span>]--;</span><br><span class="line"> count[<span class="number">1</span>]--;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> count[<span class="number">0</span>] = count[<span class="number">1</span>] = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> num : nums) {</span><br><span class="line"> <span class="keyword">if</span> (num == number[<span class="number">0</span>])</span><br><span class="line"> count[<span class="number">0</span>]++;</span><br><span class="line"> <span class="keyword">if</span> (num == number[<span class="number">1</span>])</span><br><span class="line"> count[<span class="number">1</span>]++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (count[<span class="number">0</span>] > nums.length / <span class="number">3</span>)</span><br><span class="line"> result.add(number[<span class="number">0</span>]);</span><br><span class="line"> <span class="keyword">if</span> (count[<span class="number">1</span>] > nums.length / <span class="number">3</span> && number[<span class="number">0</span>] != number[<span class="number">1</span>])</span><br><span class="line"> result.add(number[<span class="number">1</span>]);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Majority_Number_III"><a href="http://www.lintcode.com/en/problem/majority-number-iii/" target="_blank" rel="external">Majority Number III</a></h2><p>思路：<br>题目明确说明只有一个众数<br>利用多数投票算法，HashMap保存k个候选元素</p>
<ol>
<li>若HashMap中不存在num，则将num置入HashMap，对应value=1</li>
<li>若HashMap中存在num，则将对应value++</li>
<li>若HashMap的size等于k，则每个元素value–，若此时value=0，则从HashMap中删除</li>
<li>重复上述两步，直到扫描完数组</li>
<li>最后重新统计一遍HashMap中候选元素的出现次数</li>
</ol>
<p>可能出现的问题：<br><a href="http://jakezy.com/2015/08/06/java.util.ConcurrentModificationException%E5%87%BA%E7%8E%B0%E5%8E%9F%E5%9B%A0%E5%8F%8A%E8%A7%A3%E5%86%B3%E5%8A%9E%E6%B3%95/">HashMap删除元素时报错：java.util.ConcurrentModificationException</a></p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">/**</span><br><span class="line"> * <span class="doctag">@param</span> nums: A list of integers</span><br><span class="line"> * <span class="doctag">@param</span> k: As described</span><br><span class="line"> * <span class="doctag">@return</span>: The majority number</span><br><span class="line"> */</span></span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">removeKey</span><span class="params">(Map<Integer, Integer> map)</span> </span>{</span><br><span class="line"> Set<Integer> keySet = map.keySet();</span><br><span class="line"> List<Integer> remove = <span class="keyword">new</span> ArrayList<Integer>();</span><br><span class="line"> <span class="keyword">for</span> (Integer key : keySet) {</span><br><span class="line"> <span class="keyword">if</span> (map.get(key) == <span class="number">1</span>) {</span><br><span class="line"> remove.add(key);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> map.put(key, map.get(key) - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (Integer key : remove) {</span><br><span class="line"> map.remove(key);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">majorityNumber</span><span class="params">(ArrayList<Integer> nums, <span class="keyword">int</span> k)</span> </span>{</span><br><span class="line"> Map<Integer, Integer> map = <span class="keyword">new</span> HashMap<Integer, Integer>();</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> num : nums) {</span><br><span class="line"> <span class="keyword">if</span> (!map.containsKey(num)) {</span><br><span class="line"> map.put(num, <span class="number">1</span>);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> map.put(num, map.get(num) + <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (map.size() >= k) {</span><br><span class="line"> removeKey(map);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> result = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">int</span> times = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> key : map.keySet()) {</span><br><span class="line"> <span class="keyword">int</span> count = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> num : nums) {</span><br><span class="line"> <span class="keyword">if</span> (num == key)</span><br><span class="line"> count++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (count > times) {</span><br><span class="line"> times = count;</span><br><span class="line"> result = key;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/majority-element/">Majority Element</a></li>
<li><a href="https://leetcode.com/problems/majority-element-ii/">Majority Element II</a></li>
<li><a href="http://www.lintcode.com/en/problem/majority-number-iii/">Majority Number III</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 12]]></title>
<link href="http://jakezy.com/2015/08/05/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-12/"/>
<id>http://jakezy.com/2015/08/05/Leetcode刷题记录-12/</id>
<published>2015-08-05T03:16:58.000Z</published>
<updated>2015-08-06T14:05:06.271Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/single-number/" target="_blank" rel="external">Single Number</a></li>
<li><a href="https://leetcode.com/problems/single-number-ii/" target="_blank" rel="external">Single Number II</a></li>
<li><a href="http://www.lintcode.com/en/problem/single-number-iii/" target="_blank" rel="external">Single Number III</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Single_Number"><a href="https://leetcode.com/problems/single-number/" target="_blank" rel="external">Single Number</a></h2><p>思路：<br>异或：不进位加法（相同为0，相异为1）<br>a ^ a = 0<br>a ^ 0 = a<br>a ^ b = c => a ^ c = b, b ^ c = a</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">singleNumber</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> res = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span>(<span class="keyword">int</span> i = <span class="number">0</span>; i < nums.length; i++) {</span><br><span class="line"> res ^= nums[i];</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> res;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Single_Number_II"><a href="https://leetcode.com/problems/single-number-ii/" target="_blank" rel="external">Single Number II</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">singleNumber</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> res = <span class="number">0</span>;</span><br><span class="line"> <span class="comment">// count[]记录二进制每一位上1出现的次数</span></span><br><span class="line"> <span class="keyword">int</span>[] count = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">32</span>];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < <span class="number">32</span>; i++) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">0</span>; j < nums.length; j++) {</span><br><span class="line"> <span class="comment">// nums[j]右移i位再&1的结果即为nums[j]第i位的二进制值</span></span><br><span class="line"> <span class="comment">// count[i]即为第i位1出现的次数</span></span><br><span class="line"> count[i] += (nums[j] >> i & <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// count[i]%3即为res在该位的二进制值</span></span><br><span class="line"> res |= (count[i] % <span class="number">3</span>) << i;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> res;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Single_Number_III"><a href="http://www.lintcode.com/en/problem/single-number-iii/" target="_blank" rel="external">Single Number III</a></h2><p>思路：<br>使用n&-n把a和b两个只出现一次的数区分开<br>n&-n结果只保留n的二进制中第一个1出现的位置<br>n&-n = n&~(n-1)</p>
<pre><code>例如：
<span class="keyword">n</span> = 010100
-<span class="keyword">n</span> = 101100
<span class="keyword">n</span>&-<span class="keyword">n</span> = 000100
</code></pre><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> List<Integer> <span class="title">singleNumberIII</span><span class="params">(<span class="keyword">int</span>[] A)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span>[] res = <span class="keyword">new</span> <span class="keyword">int</span>[<span class="number">2</span>];</span><br><span class="line"> <span class="keyword">int</span> temp = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < A.length; i++) {</span><br><span class="line"> temp ^= A[i];</span><br><span class="line"> }</span><br><span class="line"> temp = temp & -temp;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < A.length; i++) {</span><br><span class="line"> <span class="keyword">if</span> ((temp & A[i]) == <span class="number">0</span>)</span><br><span class="line"> res[<span class="number">0</span>] ^= A[i];</span><br><span class="line"> <span class="keyword">else</span></span><br><span class="line"> res[<span class="number">1</span>] ^= A[i];</span><br><span class="line"> }</span><br><span class="line"> List<Integer> result = Arrays.asList(res[<span class="number">0</span>], res[<span class="number">1</span>]);</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/single-number/">Single Number</a></li>
<li><a href="https://leetcode.com/problems/single-number-ii/">Single Number II</a></li>
<li><a href="http://www.lintcode.com/en/problem/single-number-iii/">Single Number III</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[JDK类库]]></title>
<link href="http://jakezy.com/2015/08/04/JDK%E7%B1%BB%E5%BA%93/"/>
<id>http://jakezy.com/2015/08/04/JDK类库/</id>
<published>2015-08-04T15:14:56.000Z</published>
<updated>2015-08-09T17:15:53.378Z</updated>
<content type="html"><![CDATA[<p>详见GitBook-<a href="http://jakezy.gitbooks.io/jdk/content/" target="_blank" rel="external">JDK类库</a></p>
<p><img src="http://ww1.sinaimg.cn/large/965a04dfgw1euqz5bkuvrj20ix0ga41f.jpg" alt="JDK类库"></p>
<a id="more"></a>
<hr>
<style type="text/css">
h2, h3, h4, h5, h6 {
margin: 0 0 0 0;
}
h3, h4 {
font-size: 16px;
font-weight: normal;
}
</style>
<h1 id="集合包">集合包</h1><h2 id="Collection">Collection</h2><ul>
<li><h3 id="List">List</h3><h4 id="[ArrayList]">[ArrayList]</h4><h4 id="[LinkedList]">[LinkedList]</h4><h4 id="[Vector]">[Vector]</h4><h4 id="[Stack]">[Stack]</h4></li>
<li><h3 id="Set">Set</h3><h4 id="[HashSet]">[HashSet]</h4><h4 id="[TreeSet]">[TreeSet]</h4></li>
</ul>
<h2 id="Map">Map</h2><ul>
<li><h3 id="[HashMap]">[HashMap]</h3></li>
<li><h3 id="[TreeMap]">[TreeMap]</h3></li>
</ul>
<p>Collection接口：单对象存储的集合对象</p>
<ul>
<li>List：允许元素重复</li>
<li>Set：不允许元素重复，基于HashMap实现</li>
</ul>
<p>Map接口：key-value的集合对象</p>
<p>随着元素数量的上升（1000以上），List实现方式查找和删除元素时性能下降较严重（查找时遍历整个集合），Set、Map基本不受元素数量影响</p>
<p>TreeSet基于TreeMap实现，TreeMap删除时需排序</p>
<p>实际使用时</p>
<ol>
<li><p>根据功能需求选择List、Set或Map：<br> List：允许重复元素的单个对象集合场景<br> Set：不允许重复元素的单个对象集合场景<br> Map：key-value结构的集合场景，读远比插入删除频繁</p>
</li>
<li><p>选择相应的实现类<br> ArrayList：要通过位置来读取元素的场景（数组）<br> LinkedList：要头尾操作及插入指定位置的场景（双向链表）<br> Vector：线程安全的ArrayList场景<br> Stack：线程安全的LIFO场景</p>
<p> HashSet：无排序要求的非重复元素存放<br> TreeSet：要排序的非重复元素存放</p>
<p> HashMap：大部分key-value存取场景<br> TreeMap：要排序的key-value存取场景</p>
</li>
<li><p>根据场景中需要存储的数据量、操作、并发量进行相应性能测试，若无法满足性能要求，则需自行实现或选择并发包中的集合类</p>
</li>
</ol>
<p><hr></p>
<h1 id="并发包">并发包</h1><ul>
<li><h4 id="[ConcurrentHashMap]">[ConcurrentHashMap]</h4></li>
<li><h4 id="[CopyOnWriteArrayList]">[CopyOnWriteArrayList]</h4></li>
<li><h4 id="[CopyOnWriteArraySet]">[CopyOnWriteArraySet]</h4></li>
<li><h4 id="[ArrayBlockingQueue]">[ArrayBlockingQueue]</h4></li>
<li><h4 id="AtomicInteger"><a href="http://jakezy.com/2015/08/08/AtomicInteger/">AtomicInteger</a></h4></li>
<li><h4 id="[ThreadPoolExecutor]">[ThreadPoolExecutor]</h4></li>
<li><h4 id="[Executors]">[Executors]</h4></li>
<li><h4 id="[FutureTask]">[FutureTask]</h4></li>
<li><h4 id="[Semaphore]">[Semaphore]</h4></li>
<li><h4 id="[CountDownLatch]">[CountDownLatch]</h4></li>
<li><h4 id="[CyclicBarrier]">[CyclicBarrier]</h4></li>
<li><h4 id="[ReentrantLock]">[ReentrantLock]</h4></li>
<li><h4 id="[Condition]">[Condition]</h4></li>
<li><h4 id="[ReentrantReadWriteLock]">[ReentrantReadWriteLock]</h4></li>
</ul>
<p>提供高性能的线程安全的集合对象、并发场景需要的原子操作类、避免并发时资源冲突的Lock及Condition类</p>
]]></content>
<summary type="html">
<![CDATA[<p>详见GitBook-<a href="http://jakezy.gitbooks.io/jdk/content/">JDK类库</a></p>
<p><img src="http://ww1.sinaimg.cn/large/965a04dfgw1euqz5bkuvrj20ix0ga41f.jpg" alt="JDK类库"></p>]]>
</summary>
<category term="JDK" scheme="http://jakezy.com/tags/JDK/"/>
<category term="Java" scheme="http://jakezy.com/categories/Java/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 11]]></title>
<link href="http://jakezy.com/2015/08/03/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-11/"/>
<id>http://jakezy.com/2015/08/03/Leetcode刷题记录-11/</id>
<published>2015-08-03T06:16:58.000Z</published>
<updated>2015-08-03T16:07:09.454Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/copy-list-with-random-pointer/" target="_blank" rel="external">Copy List with Random Pointer</a></li>
<li><a href="https://leetcode.com/problems/reverse-nodes-in-k-group/" target="_blank" rel="external">Reverse Nodes in k-Group</a></li>
<li><a href="https://leetcode.com/problems/rotate-array/" target="_blank" rel="external">Rotate Array</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Copy_List_with_Random_Pointer"><a href="https://leetcode.com/problems/copy-list-with-random-pointer/" target="_blank" rel="external">Copy List with Random Pointer</a></h2><p>思路：</p>
<p>方法一：一次遍历，hashmap保存结点映射关系</p>
<p>方法二：两次遍历，先复制next，再复制random</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list with a random pointer.</span><br><span class="line"> * class RandomListNode {</span><br><span class="line"> * int label;</span><br><span class="line"> * RandomListNode next, random;</span><br><span class="line"> * RandomListNode(int x) { this.label = x; }</span><br><span class="line"> * };</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">// hashmap</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> RandomListNode <span class="title">copyRandomList</span><span class="params">(RandomListNode head)</span> </span>{</span><br><span class="line"> HashMap<RandomListNode, RandomListNode> map = <span class="keyword">new</span> HashMap<RandomListNode, RandomListNode>();</span><br><span class="line"> RandomListNode newHead = <span class="keyword">new</span> RandomListNode(<span class="number">0</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// p是待复制链表，q是复制后链表</span></span><br><span class="line"> RandomListNode p = head;</span><br><span class="line"> RandomListNode q = newHead;</span><br><span class="line"> RandomListNode node;</span><br><span class="line"> </span><br><span class="line"> <span class="comment">// 遍历链表</span></span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">// 若hashmap里已存在该结点，就将其赋值给node结点</span></span><br><span class="line"> <span class="comment">// 否则，新建结点赋值给node，并将p和node对应关系（新旧链表结点的对应关系）加入hashmap</span></span><br><span class="line"> <span class="keyword">if</span> (map.containsKey(p)) {</span><br><span class="line"> node = map.get(p);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> node = <span class="keyword">new</span> RandomListNode(p.label);</span><br><span class="line"> map.put(p, node);</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 接入新链表</span></span><br><span class="line"> q.next = node;</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 复制p的random指针</span></span><br><span class="line"> <span class="keyword">if</span> (p.random != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">// 若hashmap中存在p的random结点，则将其赋值给对应的node结点</span></span><br><span class="line"> <span class="comment">// 否则，新建结点赋值给node.random，并将p.random和node.random对应关系加入hashmap</span></span><br><span class="line"> <span class="keyword">if</span> (map.containsKey(p.random)) {</span><br><span class="line"> node.random = map.get(p.random);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> node.random = <span class="keyword">new</span> RandomListNode(p.random.label);</span><br><span class="line"> map.put(p.random, node.random);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 复制下一个结点</span></span><br><span class="line"> p = p.next;</span><br><span class="line"> q = q.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> newHead.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 两次遍历</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> RandomListNode <span class="title">copyRandomList</span><span class="params">(RandomListNode head)</span> </span>{</span><br><span class="line"> RandomListNode newHead = <span class="keyword">new</span> RandomListNode(<span class="number">0</span>);</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 第一次遍历，依次复制各结点，忽略random</span></span><br><span class="line"> RandomListNode p = head;</span><br><span class="line"> RandomListNode q = newHead;</span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span>) {</span><br><span class="line"> q.next = <span class="keyword">new</span> RandomListNode(p.label);</span><br><span class="line"> p = p.next;</span><br><span class="line"> q = q.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 第二次遍历，依次复制各结点的random指针，此时random指向的结点肯定存在</span></span><br><span class="line"> p = head;</span><br><span class="line"> q = newHead;</span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (p.random != <span class="keyword">null</span>) {</span><br><span class="line"> q.next.random = <span class="keyword">new</span> RandomListNode(p.random.label);</span><br><span class="line"> }</span><br><span class="line"> p = p.next;</span><br><span class="line"> q = q.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> newHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Reverse_Nodes_in_k-Group"><a href="https://leetcode.com/problems/reverse-nodes-in-k-group/" target="_blank" rel="external">Reverse Nodes in k-Group</a></h2><p>思路：</p>
<p>每一个group执行一次单链表反转操作</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">// 单链表反转</span></span><br><span class="line"> <span class="comment">// start: 反转部分的前一个结点，end: 反转部分的后一个结点</span></span><br><span class="line"> <span class="comment">// 返回链表尾结点</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverseList</span><span class="params">(ListNode start, ListNode end)</span> </span>{</span><br><span class="line"> ListNode last = start.next;</span><br><span class="line"> ListNode cur = last.next;</span><br><span class="line"> <span class="keyword">while</span>(cur != end) {</span><br><span class="line"> last.next = cur.next;</span><br><span class="line"> cur.next = start.next;</span><br><span class="line"> start.next = cur;</span><br><span class="line"> cur = last.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> last;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverseKGroup</span><span class="params">(ListNode head, <span class="keyword">int</span> k)</span> </span>{</span><br><span class="line"> ListNode dummy = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> dummy.next = head;</span><br><span class="line"> ListNode start = dummy;</span><br><span class="line"> <span class="keyword">int</span> i = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> i++;</span><br><span class="line"> <span class="comment">// i % k == 0 时，i的位置(head)是反转部分的最后一个结点</span></span><br><span class="line"> <span class="comment">// start是group反转后的最后一个结点，即下一个group的前一个结点</span></span><br><span class="line"> <span class="keyword">if</span> (i % k == <span class="number">0</span>) {</span><br><span class="line"> start = reverseList(start, head.next);</span><br><span class="line"> head = start.next;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> head = head.next;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> dummy.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Rotate_Array"><a href="https://leetcode.com/problems/rotate-array/" target="_blank" rel="external">Rotate Array</a></h2><p>思路：</p>
<p>前部分反转，后部分反转，整个数组反转</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">reverse</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> start, <span class="keyword">int</span> end)</span> </span>{</span><br><span class="line"> <span class="keyword">while</span> (start < end) {</span><br><span class="line"> <span class="keyword">int</span> temp = nums[start];</span><br><span class="line"> nums[start] = nums[end];</span><br><span class="line"> nums[end] = temp;</span><br><span class="line"> start++;</span><br><span class="line"> end--;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">rotate</span><span class="params">(<span class="keyword">int</span>[] nums, <span class="keyword">int</span> k)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = nums.length;</span><br><span class="line"> <span class="keyword">if</span> (n == <span class="number">0</span>) {</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> k = k % n;</span><br><span class="line"> reverse(nums, <span class="number">0</span>, n - k - <span class="number">1</span>);</span><br><span class="line"> reverse(nums, n - k, n - <span class="number">1</span>);</span><br><span class="line"> reverse(nums, <span class="number">0</span>, n - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/copy-list-with-random-pointer/">Copy List with Random Pointer</a></li>
<li><a href="https://leetcode.com/problems/reverse-nodes-in-k-group/">Reverse Nodes in k-Group</a></li>
<li><a href="https://leetcode.com/problems/rotate-array/">Rotate Array</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 10]]></title>
<link href="http://jakezy.com/2015/08/01/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-10/"/>
<id>http://jakezy.com/2015/08/01/Leetcode刷题记录-10/</id>
<published>2015-08-01T03:10:39.000Z</published>
<updated>2015-08-01T10:01:44.629Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/merge-k-sorted-lists/" target="_blank" rel="external">Merge k Sorted Lists</a></li>
<li><a href="https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/" target="_blank" rel="external">Convert Sorted List to Binary Search Tree</a></li>
<li><a href="https://leetcode.com/problems/insertion-sort-list/" target="_blank" rel="external">Insertion Sort List</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Merge_k_Sorted_Lists"><a href="https://leetcode.com/problems/merge-k-sorted-lists/" target="_blank" rel="external">Merge k Sorted Lists</a></h2><p>思路：</p>
<ol>
<li>每个链表的头结点入小根堆</li>
<li>取堆顶元素，接入newHead之后，将该元素的下一个结点入堆</li>
<li>循环第二步直到堆空</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> Comparator<ListNode> ListNodeComparator = <span class="keyword">new</span> Comparator<ListNode>() {</span><br><span class="line"> <span class="annotation">@Override</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">compare</span><span class="params">(ListNode left, ListNode right)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (left.val > right.val)</span><br><span class="line"> <span class="keyword">return</span> <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">else</span> <span class="keyword">if</span> (left.val == right.val)</span><br><span class="line"> <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">else</span></span><br><span class="line"> <span class="keyword">return</span> -<span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> };</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">mergeKLists</span><span class="params">(ListNode[] lists)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (lists.length == <span class="number">0</span>)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> Queue<ListNode> heap = <span class="keyword">new</span> PriorityQueue<ListNode>(lists.length,</span><br><span class="line"> ListNodeComparator);</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < lists.length; i++) {</span><br><span class="line"> <span class="keyword">if</span> (lists[i] != <span class="keyword">null</span>) {</span><br><span class="line"> heap.add(lists[i]);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> ListNode newHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> ListNode tail = newHead;</span><br><span class="line"> <span class="keyword">while</span> (!heap.isEmpty()) {</span><br><span class="line"> ListNode temp = heap.poll();</span><br><span class="line"> tail.next = temp;</span><br><span class="line"> tail = tail.next;</span><br><span class="line"> <span class="keyword">if</span> (temp.next != <span class="keyword">null</span>) {</span><br><span class="line"> heap.add(temp.next);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> newHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Convert_Sorted_List_to_Binary_Search_Tree"><a href="https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/" target="_blank" rel="external">Convert Sorted List to Binary Search Tree</a></h2><p>思路：</p>
<ol>
<li>找中点</li>
<li>左半部分生成BST</li>
<li>右半部分生成BST</li>
<li>循环1~3</li>
</ol>
<p>优化找中点操作为顺序遍历链表操作，挨个生成树的结点</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for a binary tree node.</span><br><span class="line"> * public class TreeNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * TreeNode left;</span><br><span class="line"> * TreeNode right;</span><br><span class="line"> * TreeNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="keyword">private</span> ListNode current;</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">getLength</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> length = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> head = head.next;</span><br><span class="line"> length++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> length;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> TreeNode <span class="title">sortedListToBST</span><span class="params">(<span class="keyword">int</span> start, <span class="keyword">int</span> end)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (start > end) {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">int</span> mid = start + (end - start) / <span class="number">2</span>;</span><br><span class="line"> TreeNode left = sortedListToBST(start, mid - <span class="number">1</span>);</span><br><span class="line"> TreeNode root = <span class="keyword">new</span> TreeNode(current.val);</span><br><span class="line"> current = current.next;</span><br><span class="line"> TreeNode right = sortedListToBST(mid + <span class="number">1</span>, end);</span><br><span class="line"> root.left = left;</span><br><span class="line"> root.right = right;</span><br><span class="line"> <span class="keyword">return</span> root;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> TreeNode <span class="title">sortedListToBST</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> current = head;</span><br><span class="line"> <span class="keyword">int</span> length = getLength(head);</span><br><span class="line"> <span class="keyword">return</span> sortedListToBST(<span class="number">0</span>, length - <span class="number">1</span>);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Insertion_Sort_List"><a href="https://leetcode.com/problems/insertion-sort-list/" target="_blank" rel="external">Insertion Sort List</a></h2><p>思路：</p>
<p>插入排序：每次将一个元素插入到已排好序的序列中的相应位置</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">insertionSortList</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode dummy = <span class="keyword">new</span> ListNode(<span class="number">0</span>); <span class="comment">// dummy链接已排好序的部分</span></span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="comment">// 从已排好序的部分中查找待插入的位置</span></span><br><span class="line"> ListNode node = dummy;</span><br><span class="line"> <span class="keyword">while</span> (node.next != <span class="keyword">null</span> && node.next.val <= head.val) {</span><br><span class="line"> node = node.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="comment">// 插入结点</span></span><br><span class="line"> ListNode temp = head.next;</span><br><span class="line"> head.next = node.next;</span><br><span class="line"> node.next = head;</span><br><span class="line"> head = temp;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> dummy.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/merge-k-sorted-lists/">Merge k Sorted Lists</a></li>
<li><a href="https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/">Convert Sorted List to Binary Search Tree</a></li>
<li><a href="https://leetcode.com/problems/insertion-sort-list/">Insertion Sort List</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 9]]></title>
<link href="http://jakezy.com/2015/07/30/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-9/"/>
<id>http://jakezy.com/2015/07/30/Leetcode刷题记录-9/</id>
<published>2015-07-30T08:15:58.000Z</published>
<updated>2015-07-30T17:03:40.509Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/delete-node-in-a-linked-list/" target="_blank" rel="external">Delete Node in a Linked List</a></li>
<li><a href="https://leetcode.com/problems/palindrome-linked-list/" target="_blank" rel="external">Palindrome Linked List</a></li>
<li><a href="https://leetcode.com/problems/intersection-of-two-linked-lists/" target="_blank" rel="external">Intersection of Two Linked Lists</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Delete_Node_in_a_Linked_List"><a href="https://leetcode.com/problems/delete-node-in-a-linked-list/" target="_blank" rel="external">Delete Node in a Linked List</a></h2><p>思路：</p>
<p>交换两前后结点，删除后一结点</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">deleteNode</span><span class="params">(ListNode node)</span> </span>{</span><br><span class="line"> node.val = node.next.val;</span><br><span class="line"> node.next = node.next.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Palindrome_Linked_List"><a href="https://leetcode.com/problems/palindrome-linked-list/" target="_blank" rel="external">Palindrome Linked List</a></h2><p>思路：</p>
<ol>
<li>找链表的中间结点，切成两条链表（head, tail）</li>
<li>挨个比较head和tail是否一致</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">findMiddle</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode dummy = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> dummy.next = head;</span><br><span class="line"> ListNode fast = dummy;</span><br><span class="line"> ListNode slow = dummy;</span><br><span class="line"> <span class="keyword">while</span> (fast != <span class="keyword">null</span> && fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> slow;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverse</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode newHead = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> ListNode temp = head.next;</span><br><span class="line"> head.next = newHead;</span><br><span class="line"> newHead = head;</span><br><span class="line"> head = temp;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> newHead;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">isPalindrome</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (head == <span class="keyword">null</span> || head.next == <span class="keyword">null</span>)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> ListNode middle = findMiddle(head);</span><br><span class="line"> ListNode tail = middle.next;</span><br><span class="line"> middle.next = <span class="keyword">null</span>;</span><br><span class="line"> tail = reverse(tail);</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span> && tail != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (head.val != tail.val) {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line"> head = head.next;</span><br><span class="line"> tail = tail.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Intersection_of_Two_Linked_Lists"><a href="https://leetcode.com/problems/intersection-of-two-linked-lists/" target="_blank" rel="external">Intersection of Two Linked Lists</a></h2><p>思路：</p>
<ol>
<li>求两链表长度，长度差为n</li>
<li>长的链表先走n步</li>
<li>同时遍历两链表，第一个相同的结点即为两链表交点</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) {</span><br><span class="line"> * val = x;</span><br><span class="line"> * next = null;</span><br><span class="line"> * }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">getIntersectionNode</span><span class="params">(ListNode headA, ListNode headB)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> lenA = <span class="number">0</span>, lenB = <span class="number">0</span>;</span><br><span class="line"> ListNode p = headA;</span><br><span class="line"> ListNode q = headB;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span>) {</span><br><span class="line"> p = p.next;</span><br><span class="line"> lenA++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">while</span> (q != <span class="keyword">null</span>) {</span><br><span class="line"> q = q.next;</span><br><span class="line"> lenB++;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">int</span> n = lenA - lenB;</span><br><span class="line"> p = n > <span class="number">0</span> ? headA : headB;</span><br><span class="line"> q = n > <span class="number">0</span> ? headB : headA;</span><br><span class="line"> n = n > <span class="number">0</span> ? n : -n;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < n; i++) {</span><br><span class="line"> p = p.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">while</span> (p != q) {</span><br><span class="line"> p = p.next;</span><br><span class="line"> q = q.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> p;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/delete-node-in-a-linked-list/">Delete Node in a Linked List</a></li>
<li><a href="https://leetcode.com/problems/palindrome-linked-list/">Palindrome Linked List</a></li>
<li><a href="https://leetcode.com/problems/intersection-of-two-linked-lists/">Intersection of Two Linked Lists</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 8]]></title>
<link href="http://jakezy.com/2015/07/29/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-8/"/>
<id>http://jakezy.com/2015/07/29/Leetcode刷题记录-8/</id>
<published>2015-07-28T17:54:58.000Z</published>
<updated>2015-07-30T17:00:16.450Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/partition-list/" target="_blank" rel="external">Partition List</a></li>
<li><a href="https://leetcode.com/problems/reorder-list/" target="_blank" rel="external">Reorder List</a></li>
<li><a href="https://leetcode.com/problems/remove-linked-list-elements/" target="_blank" rel="external">Remove Linked List Elements</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Partition_List"><a href="https://leetcode.com/problems/partition-list/" target="_blank" rel="external">Partition List</a></h2><p>思路：</p>
<p>维护两个链表，遍历原链表，小于x的接入第一个链表，不小于x的接入第二个链表，再合并两链表</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">partition</span><span class="params">(ListNode head, <span class="keyword">int</span> x)</span> </span>{</span><br><span class="line"> ListNode newHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> ListNode dummy = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> ListNode p = newHead;</span><br><span class="line"> ListNode q = dummy;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (head.val < x) {</span><br><span class="line"> p.next = head;</span><br><span class="line"> p = p.next;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> q.next = head;</span><br><span class="line"> q = q.next;</span><br><span class="line"> }</span><br><span class="line"> head = head.next;</span><br><span class="line"> }</span><br><span class="line"> p.next = dummy.next;</span><br><span class="line"> q.next = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">return</span> newHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Reorder_List"><a href="https://leetcode.com/problems/reorder-list/" target="_blank" rel="external">Reorder List</a></h2><p>思路：</p>
<p>分成三步：</p>
<ol>
<li>找链表的中间结点，切成两条链表（head, tail）</li>
<li>反转链表tail</li>
<li>合并链表head和tail，合并条件：奇数为head，偶数为tail</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">findMiddle</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode dummy = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> dummy.next = head;</span><br><span class="line"> ListNode fast = dummy;</span><br><span class="line"> ListNode slow = dummy;</span><br><span class="line"> <span class="keyword">while</span> (fast != <span class="keyword">null</span> && fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> slow;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverse</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode newHead = <span class="keyword">null</span>;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> ListNode temp = head.next;</span><br><span class="line"> head.next = newHead;</span><br><span class="line"> newHead = head;</span><br><span class="line"> head = temp;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> newHead;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">merge</span><span class="params">(ListNode head, ListNode tail)</span> </span>{</span><br><span class="line"> ListNode newHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> ListNode p = newHead;</span><br><span class="line"> <span class="keyword">int</span> n = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">while</span> (head != <span class="keyword">null</span> && tail != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (n % <span class="number">2</span> == <span class="number">0</span>) {</span><br><span class="line"> p.next = head;</span><br><span class="line"> head = head.next;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> p.next = tail;</span><br><span class="line"> tail = tail.next;</span><br><span class="line"> }</span><br><span class="line"> p = p.next;</span><br><span class="line"> n++;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (head != <span class="keyword">null</span>) {</span><br><span class="line"> p.next = head;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> p.next = tail;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">reorderList</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (head == <span class="keyword">null</span> || head.next == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span>;</span><br><span class="line"> }</span><br><span class="line"> ListNode middle = findMiddle(head);</span><br><span class="line"> ListNode tail = middle.next;</span><br><span class="line"> middle.next = <span class="keyword">null</span>;</span><br><span class="line"> tail = reverse(tail);</span><br><span class="line"> merge(head, tail);</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Remove_Linked_List_Elements"><a href="https://leetcode.com/problems/remove-linked-list-elements/" target="_blank" rel="external">Remove Linked List Elements</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">removeElements</span><span class="params">(ListNode head, <span class="keyword">int</span> val)</span> </span>{</span><br><span class="line"> ListNode dummyHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> dummyHead.next = head;</span><br><span class="line"> ListNode p = dummyHead;</span><br><span class="line"> <span class="keyword">while</span> (p.next != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (p.next.val == val) {</span><br><span class="line"> p.next = p.next.next;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> p = p.next;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> dummyHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/partition-list/">Partition List</a></li>
<li><a href="https://leetcode.com/problems/reorder-list/">Reorder List</a></li>
<li><a href="https://leetcode.com/problems/remove-linked-list-elements/">Remove Linked List Elements</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 7]]></title>
<link href="http://jakezy.com/2015/07/28/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-7/"/>
<id>http://jakezy.com/2015/07/28/Leetcode刷题记录-7/</id>
<published>2015-07-28T04:51:53.000Z</published>
<updated>2015-07-29T17:23:46.978Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/palindrome-partitioning-ii/" target="_blank" rel="external">Palindrome Partitioning II</a></li>
<li><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list/" target="_blank" rel="external">Remove Duplicates from Sorted List</a></li>
<li><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/" target="_blank" rel="external">Remove Duplicates from Sorted List II</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Palindrome_Partitioning_II"><a href="https://leetcode.com/problems/palindrome-partitioning-ii/" target="_blank" rel="external">Palindrome Partitioning II</a></h2><p>思路：</p>
<p>state: cut[j]表示子串s[0…j]所需要的最小分割次数，isPalindrome[i][j]表示字符串s的子串s[i…j]是否为回文串</p>
<p>function: </p>
<p>initialize: cut[j] = j</p>
<p>answer: cut[j-1]</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">minCut</span><span class="params">(String s)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = s.length();</span><br><span class="line"> <span class="keyword">int</span>[] cut = <span class="keyword">new</span> <span class="keyword">int</span>[n];</span><br><span class="line"> <span class="keyword">boolean</span>[][] isPalindrome = <span class="keyword">new</span> <span class="keyword">boolean</span>[n][n];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">0</span>; j < n; j++) {</span><br><span class="line"> cut[j] = j;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i <= j; i++) {</span><br><span class="line"> <span class="keyword">if</span> (s.charAt(i) == s.charAt(j)</span><br><span class="line"> && (j - i <= <span class="number">1</span> || isPalindrome[i + <span class="number">1</span>][j - <span class="number">1</span>])) {</span><br><span class="line"> isPalindrome[i][j] = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">if</span> (i > <span class="number">0</span>) {</span><br><span class="line"> cut[j] = Math.min(cut[j], cut[i - <span class="number">1</span>] + <span class="number">1</span>);</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> cut[j] = <span class="number">0</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> cut[n - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Remove_Duplicates_from_Sorted_List"><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list/" target="_blank" rel="external">Remove Duplicates from Sorted List</a></h2><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">deleteDuplicates</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode p = head;</span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span> && p.next != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">if</span> (p.val == p.next.val) {</span><br><span class="line"> p.next = p.next.next;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> p = p.next;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> head;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Remove_Duplicates_from_Sorted_List_II"><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/" target="_blank" rel="external">Remove Duplicates from Sorted List II</a></h2><p>思路：</p>
<p>引入虚节点</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">deleteDuplicates</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode dummyHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> dummyHead.next = head;</span><br><span class="line"> ListNode p = dummyHead;</span><br><span class="line"> <span class="keyword">while</span> (p.next != <span class="keyword">null</span> && p.next.next != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">int</span> val = p.next.val;</span><br><span class="line"> <span class="keyword">if</span> (p.next.val == p.next.next.val) {</span><br><span class="line"> p.next = p.next.next.next;</span><br><span class="line"> <span class="keyword">while</span> (p.next != <span class="keyword">null</span> && p.next.val == val) {</span><br><span class="line"> p.next = p.next.next;</span><br><span class="line"> }</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> p = p.next;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> dummyHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/palindrome-partitioning-ii/">Palindrome Partitioning II</a></li>
<li><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list/">Remove Duplicates from Sorted List</a></li>
<li><a href="https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/">Remove Duplicates from Sorted List II</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 6]]></title>
<link href="http://jakezy.com/2015/07/27/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-6/"/>
<id>http://jakezy.com/2015/07/27/Leetcode刷题记录-6/</id>
<published>2015-07-27T04:46:51.000Z</published>
<updated>2015-07-29T07:32:07.302Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/minimum-path-sum/" target="_blank" rel="external">Minimum Path Sum</a></li>
<li><a href="https://leetcode.com/problems/climbing-stairs/" target="_blank" rel="external">Climbing Stairs</a></li>
<li><a href="https://leetcode.com/problems/jump-game/" target="_blank" rel="external">Jump Game</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Minimum_Path_Sum"><a href="https://leetcode.com/problems/minimum-path-sum/" target="_blank" rel="external">Minimum Path Sum</a></h2><p>思路：</p>
<p>state: f[i][j]表示从起点到i,j的最短路径和</p>
<p>function: f[i][j] = min(f[i-1][j], f[i][j-1]) + cost[i][j]</p>
<p>initialize: f[0][0] = cost[0][0], f[0][i] = cost[0][i] + f[0][i-1], f[i][0] = cost[i][0] + f[i-1][0]</p>
<p>answer: f[m-1][n-1]</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">minPathSum</span><span class="params">(<span class="keyword">int</span>[][] grid)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> m = grid.length;</span><br><span class="line"> <span class="keyword">int</span> n = grid[<span class="number">0</span>].length;</span><br><span class="line"> <span class="keyword">int</span>[][] sum = <span class="keyword">new</span> <span class="keyword">int</span>[m][n];</span><br><span class="line"></span><br><span class="line"> sum[<span class="number">0</span>][<span class="number">0</span>] = grid[<span class="number">0</span>][<span class="number">0</span>];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < n; i++) {</span><br><span class="line"> sum[<span class="number">0</span>][i] = grid[<span class="number">0</span>][i] + sum[<span class="number">0</span>][i - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < m; i++) {</span><br><span class="line"> sum[i][<span class="number">0</span>] = grid[i][<span class="number">0</span>] + sum[i - <span class="number">1</span>][<span class="number">0</span>];</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < m; i++) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">1</span>; j < n; j++) {</span><br><span class="line"> sum[i][j] = grid[i][j] + Math.min(sum[i - <span class="number">1</span>][j], sum[i][j - <span class="number">1</span>]);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> sum[m - <span class="number">1</span>][n - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Climbing_Stairs"><a href="https://leetcode.com/problems/climbing-stairs/" target="_blank" rel="external">Climbing Stairs</a></h2><p>思路：</p>
<p>state: f[i]表示前i个位置跳到i的方案数</p>
<p>function: f[i] = f[i-1] + f[i-2]</p>
<p>initialize: f[0] = 1, f[1] = 2</p>
<p>answer: f[n-1]</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">climbStairs</span><span class="params">(<span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> first = <span class="number">1</span>;</span><br><span class="line"> <span class="keyword">int</span> second = <span class="number">2</span>;</span><br><span class="line"> <span class="keyword">if</span> (n == <span class="number">1</span>)</span><br><span class="line"> <span class="keyword">return</span> first;</span><br><span class="line"> <span class="keyword">if</span> (n == <span class="number">2</span>)</span><br><span class="line"> <span class="keyword">return</span> second;</span><br><span class="line"> <span class="keyword">int</span> result = <span class="number">0</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">2</span>; i < n; i++) {</span><br><span class="line"> result = first + second;</span><br><span class="line"> first = second;</span><br><span class="line"> second = result;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Jump_Game"><a href="https://leetcode.com/problems/jump-game/" target="_blank" rel="external">Jump Game</a></h2><p>思路：</p>
<p>state: f[i]表示前i个位置能否跳到第i个位置</p>
<p>function: f[i] = OR(f[j], 0 < j < i && j能跳到i)</p>
<p>initialize: f[0] = true</p>
<p>answer: f[n-1]</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="comment">// Dynamic Programming</span></span><br><span class="line"> <span class="comment">// 注：在Leetcode运行会超时</span></span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">canJump</span><span class="params">(<span class="keyword">int</span>[] nums)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = nums.length;</span><br><span class="line"> <span class="keyword">boolean</span>[] result = <span class="keyword">new</span> <span class="keyword">boolean</span>[n];</span><br><span class="line"> result[<span class="number">0</span>] = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < n; i++) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">0</span>; j < i; j++) {</span><br><span class="line"> <span class="keyword">if</span> (result[j] && nums[j] + j >= i) {</span><br><span class="line"> result[i] = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> result[n - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/minimum-path-sum/">Minimum Path Sum</a></li>
<li><a href="https://leetcode.com/problems/climbing-stairs/">Climbing Stairs</a></li>
<li><a href="https://leetcode.com/problems/jump-game/">Jump Game</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 5]]></title>
<link href="http://jakezy.com/2015/07/26/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-5/"/>
<id>http://jakezy.com/2015/07/26/Leetcode刷题记录-5/</id>
<published>2015-07-26T10:03:04.000Z</published>
<updated>2015-07-29T17:51:53.637Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/triangle/" target="_blank" rel="external">Triangle</a></li>
<li><a href="https://leetcode.com/problems/unique-paths/" target="_blank" rel="external">Unique Paths</a></li>
<li><a href="https://leetcode.com/problems/unique-paths-ii/" target="_blank" rel="external">Unique Paths II</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Triangle"><a href="https://leetcode.com/problems/triangle/" target="_blank" rel="external">Triangle</a></h2><p>思路：</p>
<p>state: f[i][j]表示从i,j出发到最后一层的最小路径和</p>
<p>function: f[i][j] = min(f[i+1][j], f[i+1][j+1]) + triangle[i][j]</p>
<p>initialize: f[n-1][j] = triangle[n-1][j]</p>
<p>answer: f[0][0]</p>
<p>可省去f[i][j]第一维空间</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">minimumTotal</span><span class="params">(List<List<Integer>> triangle)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> n = triangle.size();</span><br><span class="line"> <span class="keyword">int</span>[] sum = <span class="keyword">new</span> <span class="keyword">int</span>[n];</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 初始化终点</span></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < n; i++) {</span><br><span class="line"> sum[i] = triangle.get(n - <span class="number">1</span>).get(i);</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="comment">// 自底向上递推，更新sum[]</span></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = n - <span class="number">2</span>; i >= <span class="number">0</span>; i--) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">0</span>; j <= i; j++) {</span><br><span class="line"> sum[j] = triangle.get(i).get(j) + Math.min(sum[j], sum[j + <span class="number">1</span>]);</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> sum[<span class="number">0</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Unique_Paths"><a href="https://leetcode.com/problems/unique-paths/" target="_blank" rel="external">Unique Paths</a></h2><p>思路：</p>
<p>state: f[i][j]表示从起点到i,j的路径数</p>
<p>function: f[i][j] = f[i-1][j] + f[i][j-1]</p>
<p>initialize: f[0][i] = 1, f[j][0] = 1</p>
<p>answer: f[m-1][n-1]</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">uniquePaths</span><span class="params">(<span class="keyword">int</span> m, <span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span>[][] grid = <span class="keyword">new</span> <span class="keyword">int</span>[m][n];</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < n; i++) {</span><br><span class="line"> grid[<span class="number">0</span>][i] = <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < m; i++) {</span><br><span class="line"> grid[i][<span class="number">0</span>] = <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < m; i++) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">1</span>; j < n; j++) {</span><br><span class="line"> grid[i][j] = grid[i - <span class="number">1</span>][j] + grid[i][j - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> grid[m - <span class="number">1</span>][n - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Unique_Paths_II"><a href="https://leetcode.com/problems/unique-paths-ii/" target="_blank" rel="external">Unique Paths II</a></h2><p>思路：</p>
<p>state: f[i][j]表示从起点到i,j的路径数</p>
<p>function: f[i][j] = f[i-1][j] + f[i][j-1]</p>
<p>initialize: f[0][i] = 1, f[j][0] = 1</p>
<p>answer: f[m-1][n-1]</p>
<p>obstacleGrid[i][j]为1时表示路径不通，则grid[i][j] = 0</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">int</span> <span class="title">uniquePathsWithObstacles</span><span class="params">(<span class="keyword">int</span>[][] obstacleGrid)</span> </span>{</span><br><span class="line"> <span class="keyword">int</span> m = obstacleGrid.length;</span><br><span class="line"> <span class="keyword">int</span> n = obstacleGrid[<span class="number">0</span>].length;</span><br><span class="line"> <span class="keyword">int</span>[][] grid = <span class="keyword">new</span> <span class="keyword">int</span>[m][n];</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < m; i++) {</span><br><span class="line"> <span class="keyword">if</span> (obstacleGrid[i][<span class="number">0</span>] == <span class="number">1</span>) {</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> grid[i][<span class="number">0</span>] = <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">0</span>; j < n; j++) {</span><br><span class="line"> <span class="keyword">if</span> (obstacleGrid[<span class="number">0</span>][j] == <span class="number">1</span>) {</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> grid[<span class="number">0</span>][j] = <span class="number">1</span>;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">1</span>; i < m; i++) {</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> j = <span class="number">1</span>; j < n; j++) {</span><br><span class="line"> <span class="keyword">if</span> (obstacleGrid[i][j] == <span class="number">1</span>) {</span><br><span class="line"> grid[i][j] = <span class="number">0</span>;</span><br><span class="line"> } <span class="keyword">else</span> {</span><br><span class="line"> grid[i][j] = grid[i - <span class="number">1</span>][j] + grid[i][j - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> grid[m - <span class="number">1</span>][n - <span class="number">1</span>];</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/triangle/">Triangle</a></li>
<li><a href="https://leetcode.com/problems/unique-paths/">Unique Paths</a></li>
<li><a href="https://leetcode.com/problems/unique-paths-ii/">Unique Paths II</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 4]]></title>
<link href="http://jakezy.com/2015/07/25/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-4/"/>
<id>http://jakezy.com/2015/07/25/Leetcode刷题记录-4/</id>
<published>2015-07-25T11:28:45.000Z</published>
<updated>2015-07-29T17:51:24.763Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/reverse-linked-list/" target="_blank" rel="external">Reverse Linked List</a></li>
<li><a href="https://leetcode.com/problems/reverse-linked-list-ii/" target="_blank" rel="external">Reverse Linked List II</a></li>
<li><a href="https://leetcode.com/problems/linked-list-cycle/" target="_blank" rel="external">Linked List Cycle</a></li>
<li><a href="https://leetcode.com/problems/linked-list-cycle-ii/" target="_blank" rel="external">Linked List Cycle II</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Reverse_Linked_List"><a href="https://leetcode.com/problems/reverse-linked-list/" target="_blank" rel="external">Reverse Linked List</a></h2><p>思路：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverseList</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode p = <span class="keyword">null</span>;</span><br><span class="line"> ListNode temp;</span><br><span class="line"> <span class="keyword">while</span>(head != <span class="keyword">null</span>) {</span><br><span class="line"> temp = head.next;</span><br><span class="line"> head.next = p;</span><br><span class="line"> p = head;</span><br><span class="line"> head = temp;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> p;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Reverse_Linked_List_II"><a href="https://leetcode.com/problems/reverse-linked-list-ii/" target="_blank" rel="external">Reverse Linked List II</a></h2><p>思路：</p>
<p>m的前一个节点作为头节点，使用头插法插入m~n之间的节点，最后将m的下一个节点调整为n之后的节点</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">reverseBetween</span><span class="params">(ListNode head, <span class="keyword">int</span> m, <span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span> (head == <span class="keyword">null</span> || head.next == <span class="keyword">null</span>)</span><br><span class="line"> <span class="keyword">return</span> head;</span><br><span class="line"> ListNode fakeHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> ListNode start = fakeHead;</span><br><span class="line"> fakeHead.next = head;</span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < m - <span class="number">1</span>; i++) {</span><br><span class="line"> start = start.next;</span><br><span class="line"> }</span><br><span class="line"> ListNode end = start.next;</span><br><span class="line"> ListNode p = start.next.next;</span><br><span class="line"> ListNode q = p;</span><br><span class="line"> <span class="keyword">for</span>(<span class="keyword">int</span> i = <span class="number">0</span>; i < n - m; i++) {</span><br><span class="line"> q = p;</span><br><span class="line"> p = p.next;</span><br><span class="line"> q.next = start.next;</span><br><span class="line"> start.next = q;</span><br><span class="line"> }</span><br><span class="line"> end.next = p;</span><br><span class="line"> <span class="keyword">return</span> fakeHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Linked_List_Cycle"><a href="https://leetcode.com/problems/linked-list-cycle/" target="_blank" rel="external">Linked List Cycle</a></h2><p>思路：</p>
<p>快慢指针</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) {</span><br><span class="line"> * val = x;</span><br><span class="line"> * next = null;</span><br><span class="line"> * }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">hasCycle</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode fast = head;</span><br><span class="line"> ListNode slow = head;</span><br><span class="line"> <span class="keyword">while</span> (fast != <span class="keyword">null</span> && fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> <span class="keyword">if</span> (fast == slow) {</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Linked_List_Cycle_II"><a href="https://leetcode.com/problems/linked-list-cycle-ii/" target="_blank" rel="external">Linked List Cycle II</a></h2><p>思路：</p>
<ol>
<li>快慢指针查找相遇点</li>
<li>慢指针回到起点，快慢指针每次移动一步</li>
<li>快慢指针再次相遇点即为链表环入口</li>
</ol>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) {</span><br><span class="line"> * val = x;</span><br><span class="line"> * next = null;</span><br><span class="line"> * }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">detectCycle</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode fast = head;</span><br><span class="line"> ListNode slow = head;</span><br><span class="line"> <span class="keyword">boolean</span> flag = <span class="keyword">false</span>;</span><br><span class="line"> <span class="keyword">while</span> (fast != <span class="keyword">null</span> && fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> <span class="keyword">if</span> (fast == slow) {</span><br><span class="line"> flag = <span class="keyword">true</span>;</span><br><span class="line"> <span class="keyword">break</span>;</span><br><span class="line"> }</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">if</span> (flag == <span class="keyword">false</span>)</span><br><span class="line"> <span class="keyword">return</span> <span class="keyword">null</span>;</span><br><span class="line"> slow = head;</span><br><span class="line"> <span class="keyword">while</span> (fast != slow) {</span><br><span class="line"> fast = fast.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> fast;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/reverse-linked-list/">Reverse Linked List</a></li>
<li><a href="https://leetcode.com/problems/reverse-linked-list-ii/">Reverse Linked List II</a></li>
<li><a href="https://leetcode.com/problems/linked-list-cycle/">Linked List Cycle</a></li>
<li><a href="https://leetcode.com/problems/linked-list-cycle-ii/">Linked List Cycle II</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
<entry>
<title><![CDATA[Leetcode刷题记录 3]]></title>
<link href="http://jakezy.com/2015/07/24/Leetcode%E5%88%B7%E9%A2%98%E8%AE%B0%E5%BD%95-3/"/>
<id>http://jakezy.com/2015/07/24/Leetcode刷题记录-3/</id>
<published>2015-07-24T07:17:25.000Z</published>
<updated>2015-07-29T17:51:38.434Z</updated>
<content type="html"><![CDATA[<ul>
<li><a href="https://leetcode.com/problems/remove-nth-node-from-end-of-list/" target="_blank" rel="external">Remove Nth Node From End of List</a></li>
<li><a href="https://leetcode.com/problems/swap-nodes-in-pairs/" target="_blank" rel="external">Swap Nodes in Pairs</a></li>
<li><a href="https://leetcode.com/problems/rotate-list/" target="_blank" rel="external">Rotate List</a></li>
</ul>
<a id="more"></a>
<p><hr></p>
<h2 id="Remove_Nth_Node_From_End_of_List"><a href="https://leetcode.com/problems/remove-nth-node-from-end-of-list/" target="_blank" rel="external">Remove Nth Node From End of List</a></h2><p>思路：</p>
<p>快慢指针，慢指针找到倒数第n个前一个结点</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">removeNthFromEnd</span><span class="params">(ListNode head, <span class="keyword">int</span> n)</span> </span>{</span><br><span class="line"> ListNode fast = head;</span><br><span class="line"> ListNode slow = head;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i < n; i++) {</span><br><span class="line"> fast = fast.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">if</span> (fast == <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">return</span> head.next;</span><br><span class="line"> }</span><br><span class="line"></span><br><span class="line"> <span class="keyword">while</span> (fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> }</span><br><span class="line"> slow.next = slow.next.next;</span><br><span class="line"></span><br><span class="line"> <span class="keyword">return</span> head;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Swap_Nodes_in_Pairs"><a href="https://leetcode.com/problems/swap-nodes-in-pairs/" target="_blank" rel="external">Swap Nodes in Pairs</a></h2><p>思路：</p>
<p>交换两个节点等价于交换两个节点的val</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">swapPairs</span><span class="params">(ListNode head)</span> </span>{</span><br><span class="line"> ListNode p = head;</span><br><span class="line"> <span class="keyword">while</span> (p != <span class="keyword">null</span> && p.next != <span class="keyword">null</span>) {</span><br><span class="line"> <span class="keyword">int</span> temp = p.val;</span><br><span class="line"> p.val = p.next.val;</span><br><span class="line"> p.next.val = temp;</span><br><span class="line"> p = p.next.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">return</span> head;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>
<p><hr></p>
<h2 id="Rotate_List"><a href="https://leetcode.com/problems/rotate-list/" target="_blank" rel="external">Rotate List</a></h2><p>思路：</p>
<p>解法一：</p>
<ol>
<li>求链表长度len</li>
<li>k%len取模</li>
<li>快慢指针定位</li>
<li>交换指针</li>
</ol>
<p>解法二：<br>把整个链表连成环，找到切点再分割</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span><br><span class="line"> * Definition for singly-linked list.</span><br><span class="line"> * public class ListNode {</span><br><span class="line"> * int val;</span><br><span class="line"> * ListNode next;</span><br><span class="line"> * ListNode(int x) { val = x; }</span><br><span class="line"> * }</span><br><span class="line"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Solution</span> </span>{</span><br><span class="line"> <span class="function"><span class="keyword">public</span> ListNode <span class="title">rotateRight</span><span class="params">(ListNode head, <span class="keyword">int</span> k)</span> </span>{</span><br><span class="line"> <span class="keyword">if</span>(head == <span class="keyword">null</span>)</span><br><span class="line"> <span class="keyword">return</span> head;</span><br><span class="line"> </span><br><span class="line"> ListNode fakeHead = <span class="keyword">new</span> ListNode(<span class="number">0</span>);</span><br><span class="line"> fakeHead.next = head;</span><br><span class="line"> ListNode fast = fakeHead;</span><br><span class="line"> ListNode slow = fakeHead;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">int</span> len = <span class="number">0</span>;</span><br><span class="line"> ListNode p = head;</span><br><span class="line"> <span class="keyword">while</span>(p != <span class="keyword">null</span>) {</span><br><span class="line"> p = p.next;</span><br><span class="line"> len++;</span><br><span class="line"> }</span><br><span class="line"> </span><br><span class="line"> k = k % len;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">for</span>(<span class="keyword">int</span> i = <span class="number">0</span>; i < k; i++) {</span><br><span class="line"> fast = fast.next;</span><br><span class="line"> }</span><br><span class="line"> <span class="keyword">while</span>(fast.next != <span class="keyword">null</span>) {</span><br><span class="line"> fast = fast.next;</span><br><span class="line"> slow = slow.next;</span><br><span class="line"> }</span><br><span class="line"> fast.next = head;</span><br><span class="line"> fakeHead.next = slow.next;</span><br><span class="line"> slow.next = <span class="keyword">null</span>;</span><br><span class="line"> </span><br><span class="line"> <span class="keyword">return</span> fakeHead.next;</span><br><span class="line"> }</span><br><span class="line">}</span><br></pre></td></tr></table></figure>]]></content>
<summary type="html">
<![CDATA[<ul>
<li><a href="https://leetcode.com/problems/remove-nth-node-from-end-of-list/">Remove Nth Node From End of List</a></li>
<li><a href="https://leetcode.com/problems/swap-nodes-in-pairs/">Swap Nodes in Pairs</a></li>
<li><a href="https://leetcode.com/problems/rotate-list/">Rotate List</a></li>
</ul>]]>
</summary>
<category term="Leetcode" scheme="http://jakezy.com/tags/Leetcode/"/>
<category term="Leetcode" scheme="http://jakezy.com/categories/Leetcode/"/>
</entry>
</feed>