<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>

from functools import cache

class Solution:
    def longestPalindrome(self, s: str) -> str:

        @lru_cache(maxsize=1000)
        def isPalindrome(left, right):
            if right - left <= 1:
                return s[left] == s[right]
            
            return s[left] == s[right] and isPalindrome(left+1, right-1)

        if len(s) == 1:
            return s
        
        l_ans = r_ans = 0
        
        for l in range(len(s)):
            for r in range(l+1, len(s)):
                if s[l] != s[r]:
                    continue
                if r-l+1 <= r_ans-l_ans+1:
                    continue
                
                if isPalindrome(l, r):
                    l_ans = l
                    r_ans = r
        
        return s[l_ans:r_ans+1]
20200