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