[string]Longest Palindromic Substring

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