1040 Longest Symmetric String (25)

Given a string, you are supposed to output the length of the longest symmetric sub-string. For example, given "Is PAT&TAP symmetric?", the longest symmetric sub-string is "s PAT&TAP s", hence you must output 11.

Input Specification:

Each input file contains one test case which gives a non-empty string of length no more than 1000.

Output Specification:

For each test case, simply print the maximum length in a line.

Sample Input:

Is PAT&TAP symmetric?

Sample Output:

11

#include<cstdio>
#include<cstring>
#include<iostream>
#include<string>
using namespace std;
const int maxn = 1010;
string s;
int dp[maxn][maxn];
int main(){
  getline(cin,s);
  //while(scanf("%s",s) != EOF);
    int len = s.length(), ans = 1;
    memset(dp,0,sizeof(dp));
    for(int i = 0; i < len; i++){
        dp[i][i] = 1;
        if(i < len - 1){
            if(s[i] == s[i+1]){
                dp[i][i+1] = 1;
                ans = 2;
            }
        }
    }
    for(int L = 3; L <= len; L++){
        for(int i = 0; i + L - 1 < len; i++){
            int j = i+L-1;
            if(s[i] == s[j] && dp[i+1][j-1] == 1){
                dp[i][j] = 1;
                ans = L;
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}