POJ 3974 Palindrome（最长回文子串）

题目链接：http://poj.org/problem?id=3974

题意：求一给定字符串最长回文子串的长度

思路：直接套模板manacher算法

code：

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 const int MAXN = ;
 char Ma[*MAXN];
 int Mp[*MAXN];

 void Manacher(char s[], int len)
 {
     int l = ;
     Ma[l++] = 'S';
     Ma[l++] = '#';
     for (int i = ; i < len; ++i)
     {
         Ma[l++] = s[i];
         Ma[l++] = '#';
     }
     Ma[l] = ;
     int mx = ;
     int id = ;
     for (int i = ; i < l; ++i)
     {
         Mp[i] = mx > i ? min(Mp[*id-i], mx-i) : ;
         while (Ma[i+Mp[i]] == Ma[i-Mp[i]]) ++Mp[i];
         if (i + Mp[i] > mx)
         {
             mx = i +Mp[i];
             id = i;
         }
     }
 }

 char s[MAXN];

 int main()
 {
     int cnt = ;
     while (scanf("%s", s) != EOF)
     {
         if (strcmp(s, "END") == ) break;
         int len = strlen(s);
         Manacher(s, len);
         int ans = ;
         len =  * len + ;
         for (int i = ; i < len; ++i) ans = max(ans, Mp[i] - );
         printf("Case %d: %d\n",++cnt, ans);
     }
     return ;
 }