[LeetCode] Longest Palindromic Substring

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

class Solution {
public:
    string longestPalindrome(string s) {
        int len = s.size();
        if(len <= 1) return s;
        bool dp[len][len];
        memset(dp, 0, sizeof(dp));
        int ansleft = 0,ansright = 0;
        for(int i = 1;i < len;i ++){
            dp[i][i] = true;
            dp[i][i - 1] = true;
        }
        for(int k = 2;k <= len;k ++){
            for(int i = 0;i <= len - k;i ++){
                if(s[i] == s[i + k - 1] && dp[i + 1][i + k - 2] == true){
                    dp[i][i + k - 1] = true;
                    if(ansright - ansleft + 1 < k){
                        ansleft = i;
                        ansright = i + k - 1;
                    }
                }
            }
        }
        return s.substr(ansleft,ansright - ansleft + 1);
    }
};

參考