647

Author: LuYanFCP

README.md

@@ -51,6 +51,10 @@ Leetcode刷题记录
 + No.211 [cpp](cpp/211.cpp)
 + No.212 [cpp](cpp/212.cpp)
 
+### 字符串
+
++ No.647 [cpp](cpp/647.cpp)  **回文串算法**
+
 ### 栈
 
 + No.32 [cpp](cpp/32.cpp) [python](python/32.py)

cpp/647.cpp

@@ -0,0 +1,111 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define PRINT_VECTOR(vec, type) \
+do { \
+    copy(vec.begin(), vec.end(), ostream_iterator<type>(cout, " ")); \
+    cout << endl; \
+} while(0)
+
+#define CHECK(j, k, m)  ((j) >= 0) && ((k) < (m))
+
+
+class Solution {
+public:
+    /**
+     * 
+     */
+	int countSubstrings(string s)
+	{
+        ostringstream strbuf;
+        strbuf << "#";
+        for (const char &c: s) {
+            strbuf << c << "#";
+        }
+        string str = strbuf.str();
+        // #a#b#c#
+        int m = str.size();
+        vector<int> radius(m, 0); 
+
+        int r_radius = 0, mid_index = 0, count = 0;
+        for (int i = 0; i < m; ++i) {
+            
+            if (i <= r_radius + mid_index) {
+                // 对称位置是否超出右边的限制
+                // printf("%d, %d\n", radius[mid_index*2-i], mid_index+r_radius-i);
+                radius[i] = min(radius[mid_index*2-i], mid_index+r_radius-i);
+            }
+            #if 0
+            printf("radius[%d]=%d ", i, radius[i]);
+            printf(" str[i]=%c ", str[i]);
+            printf("str[i-radius[i]-1]=%c, str[i+radius[i]+1]=%c ", str[i-radius[i]-1], str[i+radius[i]+1] );
+            printf("%d ===> %d,%d\n", CHECK(i-radius[i]-1, i+radius[i]+1, m), i, str[i-radius[i]-1] == str[i + radius[i]+1]);
+            #endif
+            while (CHECK(i-radius[i]-1, i+radius[i]+1, m) && str[i-radius[i]-1] == str[i+radius[i]+1]) {
+                ++radius[i];
+            }
+            
+            if (mid_index + r_radius < i + radius[i]) {
+                r_radius = radius[i];
+                mid_index = i;
+            }
+            count += (radius[i]+1)/2;
+        }
+        // PRINT_VECTOR(radius, int);
+        return count;
+    }
+};
+
+#if 0
+
+#define CHECK(j, k, m)  ((j) >= 0) && ((k) < (m))
+
+    /** 基础算法*/
+    int countSubstrings(string s) {
+        ostringstream str;
+        int n = s.size(), count = 0;
+        for (int i = 0; i < n; ++i) {
+
+            str << "#" << s[i];
+        }
+        str << '#';
+        string ss = str.str();
+
+        int j, k, m = ss.size(), flag_num;
+        for (int i = 1; i < m; ++i) {
+            j = i - 1, k = i + 1;
+            flag_num = ss[i] == '#'? 1:0;
+            while(CHECK(j, k, m)) {
+                if (ss[j]=='#') flag_num++;
+                if (ss[j] == ss[k]){
+                    if (ss[j]=='#') {
+                        if (flag_num < 2) count++;
+                    } else {
+                        count++;
+                    }
+                } 
+                else break;
+                j--;
+                k++;
+            }
+        }
+        return count;
+    }
+#endif
+
+
+int main(int argc, char const *argv[])
+{
+    Solution s;
+    freopen("test.in", "r", stdin);
+    string str;
+    while (cin >> str) {
+        /* code */
+        cout << str << endl;
+        int result = s.countSubstrings(str);
+        cout << result << endl;
+    }
+    
+    return 0;
+}