<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:
        n = len(s)
        dp  = [[0] * n for _ in s]
        max_len = 1
        start = 0

        for i in range(0, n):
            dp[i][i] = 1

        for i in range(0, n-1):
            if(s[i] == s[i+1]):
                dp[i][i+1] = 1
                max_len = 2
                start = i

        for k in range(3, n+1):
            for i in range(n-k+1):
                j = i+k-1
                if(s[i] == s[j] and dp[i+1][j-1] == 1):
                    dp[i][j] = 1
                    max_len = k
                    start = i
        

            

        return s[start:start+max_len]

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