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：

 1 class Solution {
 2 public:
 3     string longestPalindrome(string s) {
 4         if (!s.size()) return "";
 5         string ret;
 6         string tmp;
 7         for (int i = 0; i < s.size(); ++i){
 8             tmp = findPal(s, i - 1, i + 1);
 9             if (tmp.size() > ret.size())
10                 ret = tmp;
11             tmp = findPal(s, i , i + 1);
12             if (tmp.size() > ret.size())
13                 ret = tmp;
14         }
15         return ret;
16     }
17
18     string findPal(string & s,  int left, int right)
19     {
20         if (left < 0)
21             return s.substr(left + 1, 1);
22         if (right >= s.size())
23             return s.substr(right - 1, 1);
24
25         while (left >= 0 && right < s.size()){
26             if (s[left] != s[right])
27                 break;
28             left--;
29             right++;
30         }
31         left++;
32         return s.substr(left, right - left);
33     }
34 };