<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:
        candidates = []
        for i in range(len(s)):
            if i > 0 and i + 1 < len(s) and s[i-1] == s[i+1]:
                subStr = self.getPalindrome(s, i-1, i+1)
                candidates.append(subStr)
            if i + 1 < len(s) and s[i] == s[i+1]:
                subStr = self.getPalindrome(s, i, i+1)
                candidates.append(subStr)
        
        if len(candidates) == 0:
            return s[0]
            
        maxLen = 1
        result = ""
        for candidate in candidates:
            if len(candidate) > maxLen:
                result = candidate
                maxLen = len(candidate)
        
        return result
    
    def getPalindrome(self, s:str, l:int, r:int) -> str:
        while l >= 0 and r < len(s):
            if l-1 >= 0 and r+1 < len(s) and s[l-1] == s[r+1]:
                l -= 1
                r += 1
            else:
                break
        return s[l:r+1]
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