leetcode 练习题 -- 5. Longest Palindromic Substring

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本文介绍了一种寻找字符串中最长回文子串的方法。通过双重循环遍历字符串，利用辅助函数判断子串是否为回文，并记录最长回文子串的位置及长度，最终返回最长回文子串。

Description

Given a string s, find the longest palindromic substring ins. You may assume that the maximum length ofs is 1000.

Example:

Input: "babad"

Output: "bab"

Note: "aba" is also a valid answer.

Example:

Input: "cbbd"

Output: "bb"

class Solution {
public:
	bool huiwen(string s)
	{
		int i = 0, j = s.length() - 1;

		if (j == 0)return true;

		while (i <= j)
		{
			if (s[i] != s[j])
				return false;
			else
			{
				i++; j--;
			}
		}
		return true;
	}
	string longestPalindrome(string s) {
		int sum = 0, max = 0;
		int a;
		if (s.length() == 1)return s;
		for (int i = 0; i<s.length() - 1; i++)
		{
			sum = 0;
			for (int j = i; j < s.length(); j++)
			{
				if (s[i] == s[j])
				{
					sum = j - i + 1;
					if (sum > max)
					{
						if (huiwen(s.substr(i, sum)))
						{
							a = i;
							max = sum;
						}
					}
				}
			}
		}
		return s.substr(a, max);
	}
};