<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:
    def longestPalindrome(self, s: str) -> str:
        if len(s)<=1:
            return s
        ml=1
        ms=s[0]
        dp=[[False for i in range(len(s))] for i in range(len(s))]
        for i in range(len(s)):
            dp[i][i]=True
            for j in range(i):
                if s[j]==s[i] and (i-j <=2 or dp[j+1][i-1]):
                    dp[j][i]=True
                    if i-j+1>ml:
                        ml=i-j+1
                        ms=s[j:i+1]
        return ms
    
    
        
25200