5. 最长回文子串

#include<iostream>
#include<stdio.h>
#include<cstdio>
#include<vector>
#include <algorithm>
#include <functional>
#include<string>
#include<fstream>
#include <sstream>
#include <assert.h>
using namespace std;
class Solution {
public:
	string longestPalindrome(string s)
	{
		if (s.length() < 0) return "";//如果长度小于0则返回空
		int n = s.size();//获得字符串的长度
		vector<vector<bool>> dp(n, vector<bool>(n, false));//定义bool向量
		int maxlen = 1, start = 0;
		for (int i = 0; i < n; i++)
		{
			for (int j = 0; j <= i; j++)
			{
				if (i - j < 2) dp[i][j] = (s[i] == s[j]);
				else
					dp[i][j] = (s[i] == s[j] && dp[i - 1][j + 1] == 1);
				if (dp[i][j] && maxlen < i - j + 1)
				{
					maxlen = i - j + 1;
					start = j;
				}
			}
		}
		return s.substr(start, maxlen);
	}

};

string stringToString(string input) {
	assert(input.length() >= 2);
	string result;
	for (int i = 1; i < input.length() - 1; i++) {
		char currentChar = input[i];
		if (input[i] == '\') {
			char nextChar = input[i + 1];
			switch (nextChar) {
			case '"': result.push_back('"'); break;
			case '/': result.push_back('/'); break;
			case '\': result.push_back('\'); break;
			case 'b': result.push_back(''); break;
			case 'f': result.push_back('f'); break;
			case 'r': result.push_back('
'); break;
			case 'n': result.push_back('
'); break;
			case 't': result.push_back('	'); break;
			default: break;
			}
			i++;
		}
		else {
			result.push_back(currentChar);
		}
	}
	return result;
}

int main() {
	string line;
	while (getline(cin, line)) {
		string s = stringToString(line);

		string ret = Solution().longestPalindrome(s);

		string out = (ret);
		cout << out << endl;
	}
	return 0;
}

　　

# 给定一个字符串 s，找到 s 中最长的回文子串。你可以假设 s 的最大长度为 1000。
# 示例 1：
# 输入: "babad"
# 输出: "bab"
# 注意: "aba" 也是一个有效答案。
# 示例 2：
# 输入: "cbbd"
# 输出: "bb"
# 解题思路：
# 正着与倒着比.
import sys
class Solution:
    def zuichanghuiwen(self, s):
        if len(s) <= 1:
            return s
        for length in range(len(s), 0, -1):
            for i in range(0, len(s) - length + 1):
                now_s = s[i:i + length]
                if now_s == now_s[::-1]:
                    return now_s
if __name__ == '__main__':
    s = sys.stdin.readline().strip()
    ret = Solution().zuichanghuiwen(s)
    print(ret)