<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)

        def __lps(l: int, r: int, lps: str=""):
            if l < 0 or r > n-1:
                return lps

            if l == r:
                lps = s[l]
            elif s[l] == s[r]:
                lps = s[l] + lps + s[r]
            else:
                return lps
            return __lps(l-1, r+1, lps)

        longest_lps = ""

        for i in range(n):
            odd = __lps(i, i)
            even = __lps(i, i+1)

            if len(odd) > len(longest_lps): longest_lps = odd
            if len(even) > len(longest_lps): longest_lps = even
        return longest_lps
    
17000