Leetcode Hot100 第66题 5.最长回文子串

class Solution {
public:
    string longestPalindrome(string s) {
        // dp[i][j]表示以s[i...j]是否为回文子串
        int n = s.size();
        int res = 1;
        int start = 0;
        vector<vector<bool>> dp(n,vector<bool>(n,true));
        for(int j=1;j<n;j++){
            for(int i=j-1;i>=0;i--){
                if(s[i]==s[j]){
                    dp[i][j] = dp[i+1][j-1];
                }else{
                    dp[i][j] = false;
                }
                if(dp[i][j]){
                    if(j-i+1>res){
                        res = j-i+1;
                        start = i;
                    }
                }
            }
        }
        return s.substr(start,res);
    }
};