九度oj 1528 最长回文子串

 1 #include<algorithm>
 2 #include<iostream>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<cstdio>
 6 using std::max;
 7 const int Max_N = 200010;
 8 char ret[Max_N];
 9 void solve() {
10     int i, j, ans = 0, n = strlen(ret);
11     for (i = 0; i < n; i++) {
12         for (j = 0; i >= j && i + j < n; j++) {
13             if (ret[i - j] != ret[i + j]) break;
14             ans = max(ans, j << 1 | 1);
15         }
16         for (j = 0; i >= j && i + j + 1 < n; j++) {
17             if (ret[i - j] != ret[i + j + 1]) break;
18             ans = max(ans, (j << 1) + 2);
19         }
20     }
21     printf("%d\n", ans);
22 }
23 int main() {
24 #ifdef LOCAL
25     freopen("in.txt", "r", stdin);
26     freopen("out.txt", "w+", stdout);
27 #endif
28     while (gets(ret)) solve();
29     return 0;
30 }