<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) < 3:
            if s[0] == s[-1]:
                return s
            else:
                return s[0]

        dp = [[False for _ in range(len(s) - i)] for i in range(len(s))]

        dp[-1][0] = True

        for i in range(len(s) - 1):
            dp[i][0] = True
            dp[i][1] = True if s[i] == s[i + 1] else False
        
        for i in range(len(dp) - 3, -1, -1):
            for j in range(2, len(dp[i])):
                if dp[i + 1][j - 2] and s[i] == s[i + j]:
                    dp[i][j] = True

        max = [0, 0]
        for i in range(len(dp)):
            for j in range(len(dp[i])):
                if dp[i][j] and j > max[1]:
                    max[0], max[1] = i, j

        return s[max[0]:max[0] + max[1] + 1:1]



        

        
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