<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
        
        ans = ""
        
        f = [[False] * len(s) for _ in range(len(s))]

        for i in range(len(s)):
            for j in range(i, -1, -1):
                if i == j:
                    f[i][j] = True
                elif i - j == 1:
                    f[i][j] = (s[i] == s[j])
                elif i - j > 1:
                    f[i][j] = (s[i] == s[j] and f[i - 1][j + 1])
                
                if f[i][j] and i - j + 1 > len(ans):
                    ans = s[j: i + 1]
                
        return ans
24600