leetcode每日一题

5.最长回文子串

// 5.最长回文子串
//baolifa
class Solution {
public:
	string longestPalindrome(string s) {
		string tmp = "";
		string res = "";
		for (int i=0;i<s.length();i++)
		{
			for (int j=i;j<s.length();j++)
			{
				tmp += s[j];
				string tmp1 = tmp;
				reverse(tmp1.begin(), tmp1.end());
				if (tmp1==tmp)
				{
					res = res.length() > tmp.length() ? res : tmp;
				}
			}
			tmp = "";
		}
		return res;
	}
};
//解法2
//将字符串s反转得到字符串rev，再求他们的最长公共子串，再判断该最长公共子串是否就是我们要找的最长回文子串。
class Solution {
public:
	string longestPalindrome(string s) {
		string tmp = "";
		string res = "";
		string rev = s;
		int len = 0;
		reverse(rev.begin(), rev.end());
		for (int i = 0; i < s.length(); i++)
		{
			for (int j = i; j < s.length(); j++)
			{
				tmp += s[j];
				if (tmp.length() < len)
				{
					continue;
				}
				else if (rev.find(tmp) != -1) {
					string tmp1 = tmp;
					reverse(tmp1.begin(), tmp1.end());
					if (tmp1==tmp)
					{
						len = tmp.length(); res = tmp;
					}
				}
				else
				{
					break;
				}
			}
			tmp = "";
		}
		return res;
	}
};