最长回文串

class Solution {
public:
    string longestPalindrome(string s)
    {
        int ans1 = 0, ans2 = 0;
        for(int i = 0; i < s.size(); )
        {
            int l = i, r = i;
            while(r < s.size() && s[r + 1] == s[i])
                r++;
            i = r + 1;
            while(l >= 0 && r < s.size() && s[l] == s[r])
                l--,r++;
            if(r - l > ans2 - ans1)
            {
                ans1 = l;
                ans2 = r;
            }
        }
        return s.substr(ans1 + 1, ans2 - ans1 - 1);
    }
};