力扣5 最长回文子串

// leetcode.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include "pch.h"
#include<vector>
#include<string>
#include<iostream>
using namespace std;
#define max(a,b) (((a)>(b))? (a):(b))
#define min(a,b) (((a)<(b))? (a):(b))


class Solution {
public:
	string longestPalindrome(string s)
	{
		
		int len = s.size();
		if (len == 0 || len == 1)
			return s;
		int cur_len = 0;
		int max_len = 1;
		int start = 0;
		vector<vector<bool>>dp(len,vector<bool>(len));//二维动态数组的初始化要注意
		for (int l = 0; l < len; l++)
		{
			for (int r = 0; r < len; r++)
			{
				if (l == r)
				{
					dp[l][r] = true;
				}
				else
				{
					dp[l][r] = false;
				}
				
			}
		}
		for (int r = 1; r < len; r++)
		{
			for (int l=0; l < r; l++)
			{
				if (s[l] == s[r])
				{
					if (r - l < 3)
					{
						dp[l][r] = true;
					}
					else
					{
						dp[l][r] = dp[l + 1][r - 1];
					}
				}
				else
				{
					dp[l][r] = false;
				}
				if (dp[l][r]) 
				{
					cur_len = r - l + 1;
					if (cur_len > max_len)
					{
						max_len = cur_len;
						start = l;
					}
				}
					
			}
		}
		return s.substr(start, max_len);

		
	}
	
};
int main(int argc, char *argv[])
{
	

	Solution solution;
	string ret = solution.longestPalindrome("cbbd");
	cout << ret;
	return 0;
}

vector<vector<bool>>dp(len,vector(len));//二维动态数组的初始化要注意

因为一个二维向量vector<vector >，初始只能确定列数，但是无法确定行数
所以需要明确说明行数
一般有下列俩中初始化方法