【力扣 | 01】5. 最长回文子串

5. 最长回文子串

解法：

class Solution {
public:
    string longestPalindrome(string s) 
    {
        if(s.size() < 2) return s;
        string result;
        vector<vector<bool>> dp(s.size() + 1, vector<bool>(s.size() + 1, false));
        for(int i = 0; i < s.size(); i++) dp[i][i] = true;

        int maxLen = 0;
        int beginIndex = 0;
        for(int i = s.size() - 1; i >= 0; i--) 
        {
            for(int j = i; j < s.size(); j++) 
            {
                if(s[i] == s[j]) 
                {
                    if(j - i<= 1) 
                        dp[i][j] = true;                  
                    else if(dp[i+1][j-1]) 
                        dp[i][j] = true;
                }
                if (dp[i][j] && j - i + 1 > maxLen) 
                {
                    maxLen = j - i + 1;
                    beginIndex = i;
                }
            }
        }
        result = s.substr(beginIndex,maxLen);
        return result;
    }
};