LeetCode 5. 最长回文子串

class Solution {
public:
    string longestPalindrome(string s) {
        int start = 0, end = 0;
        for (int i = 0; i < s.size(); ++i)
        {   
            findLongest(s, i, i, start, end);
            findLongest(s, i, i + 1, start, end);
        }
        return s.substr(start, end - start + 1);
    }

    void findLongest(string s, int left, int right, int& start, int& end)
    {
        while (left >= 0 && right < s.size() && s[left] == s[right])
        {
            --left;
            ++right;
        }
        left = left + 1;
        right = right - 1;
        if (right - left > end - start)
        {
            start = left;
            end = right;
        }
    }
};