LeetCode OJ：Longest Palindromic Substring（最长的回文字串）

 

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.

玩了两天dota2,罪过罪过，还是应该老老实实刷题啊。

题目求得是最长的回文子串，这里使用的是暴力的解法，也就是解决两种回文"asdsa"以及"assa"，即奇数以及偶数回文，相当于用了二重循环，代码如下：

class Solution {
public:
    string longestPalindrome(string s) {
        if (!s.size()) return "";
        string ret;
        string tmp;
        for (int i = 0; i < s.size(); ++i){
            tmp = findPal(s, i - 1, i + 1);
            if (tmp.size() > ret.size())
                ret = tmp;
            tmp = findPal(s, i , i + 1);
            if (tmp.size() > ret.size())
                ret = tmp;
        }
        return ret;
    }
    
    string findPal(string & s,  int left, int right)
    {
        if (left < 0)
            return s.substr(left + 1, 1);
        if (right >= s.size())
            return s.substr(right - 1, 1);

        while (left >= 0 && right < s.size()){
            if (s[left] != s[right])
                break;
            left--;
            right++;
        }
        left++;
        return s.substr(left, right - left);
    }
};