5. Longest Palindromic Substring

class Solution {public:    string longestPalindrome(string s) {        bool flag [1000][1000] = {false};        int sz = s.size(), maxLen = 1, start = 0;        for(int i = 0; i < sz; ++i)            flag[i][i] = true;        for(int i = 0; i < sz-1; ++i){            if(s[i]==s[i+1]){                flag[i][i+1] = true;                maxLen = 2;                start = i;            }        }        for(int len = 3; len <= sz; ++len){            for(int i = 0; i <= sz-len; ++i){                if(s[i] == s[i+len-1] && flag[i+1][i+len-2]){                    flag[i][i+len-1] = true;                    maxLen = len;                    start = i;                }            }        }        return s.substr(start, maxLen);    }};