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.length();    int i, j, m = 0, max = 0, left, right;    m = len;    for(i=0; i<m; i++)  //以i为中心，判断是否为回文串    {        for(j=0; i-j>=0 && i+j<m; j++)  //长度为奇数        {            if(s[i-j] != s[i+j])                break;            if(j*2+1 > max)            {                max = j * 2 + 1;                left = i-j;                right = i+j;            }        }        for(j=0; i-j>=0 && i+j+1<m; j++)  //长度为偶数        {            if(s[i-j] != s[i+j+1])                break;            if(j*2+2 > max)            {                max = j * 2 + 2;                left = i-j;                right = i+j+1;            }        }    }    string sub;    for(i=left; i<=right; i++)        sub += s[i];    return sub;    }};