<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)<2:
            return s

        n = len(s)
        dp = [[False]*n for _ in range(n)]
        start_ind = 0
        max_len = 1

        for i in range(n):
            dp[i][i] = True
        
        for i in range(n-1, -1, -1):
            for j in range(i+1, n):
                if s[i]==s[j]:
                    if j-i<=2:
                        dp[i][j] = True
                    else:
                        dp[i][j] = dp[i+1][j-1]
                    
                    if dp[i][j] == True:
                        if j-i+1 > max_len:
                            start_ind = i
                            max_len = j-i+1
        
        return s[start_ind:start_ind+max_len]
23800