<p>Given a string <code>s</code>, return <em>the longest</em> <span data-keyword="palindromic-string"><em>palindromic</em></span> <span data-keyword="substring-nonempty"><em>substring</em></span> in <code>s</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;babad&quot;
<strong>Output:</strong> &quot;bab&quot;
<strong>Explanation:</strong> &quot;aba&quot; is also a valid answer.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;cbbd&quot;
<strong>Output:</strong> &quot;bb&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consist of only digits and English letters.</li>
</ul>

class Solution {
public:
    // bool checkPalindrome(string &s, int i,int j){
    //     while(i<=j){
    //         if(s[i]==s[j]){
    //             i++;
    //             j--;
    //         }else{
    //             return false;
    //         }
    //     }
    //     return true;
    // }
vector<vector<int>> dp;
    int checkPalindrome(string &s, int i,int j){
        if(i>=j)return 1;

        if(dp[i][j]!=-1)return dp[i][j];
        if(s[i]==s[j]){
            return dp[i][j] = checkPalindrome(s,i+1,j-1);
        }
        return 0;
    }
    
    string longestPalindrome(string s) {
        int maxLength =  INT_MIN;
        int sp = 0;
        dp.resize(1001,vector<int>(1001,-1));
        for(int i=0;i<s.size();i++){
            for(int j=i;j<s.size();j++){
                if(checkPalindrome(s,i,j)){
                    if(j-i+1>maxLength){
                        maxLength = j-i+1;
                        sp = i;
                    }
                }
            }
        }
        return s.substr(sp,maxLength);
    }
};
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