提交作业

Author: YorkPeng

225.用队列实现栈.java

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+import java.util.LinkedList;
+import java.util.Queue;
+
+/*
+ * @lc app=leetcode.cn id=225 lang=java
+ *
+ * [225] 用队列实现栈
+ */
+
+// @lc code=start
+class MyStack {
+    Queue<Integer> queue1;
+    Queue<Integer> queue2;
+
+    /** Initialize your data structure here. */
+    public MyStack() {
+        queue1 = new LinkedList<>();
+        queue2 = new LinkedList<>();
+    }
+    
+    /** Push element x onto stack. */
+    public void push(int x) {
+        queue1.add(x);
+    }
+    
+    /** Removes the element on top of the stack and returns that element. */
+    public int pop() {
+        while(queue1.size()>1){
+            queue2.add(queue1.poll());
+        }
+        int temp = queue1.poll();
+
+        while(!queue2.isEmpty()){
+            queue1.add(queue2.poll());
+        }
+
+        return temp;
+    }
+    
+    /** Get the top element. */
+    public int top() {
+        while(queue1.size()>1){
+            queue2.add(queue1.poll());
+        }
+        int temp = queue1.peek();
+
+        queue2.add(queue1.poll());
+
+        while(!queue2.isEmpty()){
+            queue1.add(queue2.poll());
+        }
+        return temp;
+    }
+    
+    /** Returns whether the stack is empty. */
+    public boolean empty() {
+        return queue1.isEmpty();
+    }
+}
+
+/**
+ * Your MyStack object will be instantiated and called as such:
+ * MyStack obj = new MyStack();
+ * obj.push(x);
+ * int param_2 = obj.pop();
+ * int param_3 = obj.top();
+ * boolean param_4 = obj.empty();
+ */
+// @lc code=end
+

232.用栈实现队列.java

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+import java.util.Stack;
+
+/*
+ * @lc app=leetcode.cn id=232 lang=java
+ *
+ * [232] 用栈实现队列
+ */
+
+// @lc code=start
+class MyQueue {
+
+    Stack<Integer> stack1;
+    Stack<Integer> stack2;
+
+    /** Initialize your data structure here. */
+    public MyQueue() {
+        stack1 = new Stack<Integer>();
+        stack2 = new Stack<Integer>();
+    }
+    
+    /** Push element x to the back of queue. */
+    public void push(int x) {
+        stack1.push(x);
+    }
+    
+    /** Removes the element from in front of queue and returns that element. */
+    public int pop() {
+        while(!stack1.empty()){
+            stack2.push(stack1.pop());
+        }
+        int temp = stack2.pop();
+        while(!stack2.empty()){
+            stack1.push(stack2.pop());
+        }
+        return temp;
+    }
+    
+    /** Get the front element. */
+    public int peek() {
+        while(!stack1.empty()){
+            stack2.push(stack1.pop());
+        }
+        int temp = stack2.peek();
+        while(!stack2.empty()){
+            stack1.push(stack2.pop());
+        }
+        return temp;
+    }
+    
+    /** Returns whether the queue is empty. */
+    public boolean empty() {
+        if(stack1.empty()){
+            return true;
+        }
+        return false;
+    }
+}
+
+/**
+ * Your MyQueue object will be instantiated and called as such:
+ * MyQueue obj = new MyQueue();
+ * obj.push(x);
+ * int param_2 = obj.pop();
+ * int param_3 = obj.peek();
+ * boolean param_4 = obj.empty();
+ */
+// @lc code=end
+

263.丑数.java

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+/*
+ * @lc app=leetcode.cn id=263 lang=java
+ *
+ * [263] 丑数
+ */
+
+// @lc code=start
+class Solution {
+    public boolean isUgly(int num) {
+        if(num < 1){
+            return false;
+        }
+        while(num%5==0){
+            num/=5;
+        }
+        while(num%3==0){
+            num/=3;
+        }
+        while(num%2==0){
+            num/=2;
+        }
+        if(num == 1){
+
+            return true;
+        }
+        return false;
+    }
+}
+// @lc code=end
+