LeetCode 5 Longest Palindromic Substring

C.R.A.zy

于 2020-03-17 23:11:20 发布

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文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/weixin_43350346/article/details/104934112

版权

本文介绍了一种解决LeetCode经典题目“寻找最长回文子串”的算法实现，通过使用动态规划方法，有效地找到了给定字符串中最长的回文子串。

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Problem

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

Example 1:
Input: “babad”
Output: “bab”
Note: “aba” is also a valid answer.

Example 2:
Input: “cbbd”
Output: “bb”

Solution

class Solution {
public:
    string longestPalindrome(string s) {
        int n=s.size();
        string res="";
        int l=0; 
        res=s[0];
        vector<vector<bool>> dp(n, vector<bool>(n));
          for (int j = 0; j<n; j++) 
          {
            for (int i=j;i>=0;i--)
            {
                if((s[i] == s[j]) && (j - i <= 2 || dp[i + 1][j - 1]))
                {
                    dp[i][j]=true;
                    if(j-i>l)
                    {
                        res=s.substr(i,j-i+1);
                        l=j-i;
                    }
                }
            }
        }
        return res;
    }
};