<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 not s:
            return ""
        dp = [[0]*i for i in range(1,len(s)+1)]
        for i in dp:
            i[-1]=1
        max_length = 1
        maxx=0
        maxy=0
        for i in range(1,len(s)):
            for j in range(i):
                if j==i-1:
                    if s[j]==s[i]:
                        dp[i][j]=1
                        if max_length<2:
                            max_length =2
                            maxx=i
                            maxy =j
                    break
                elif dp[i-1][j+1] == 1:
                    if s[j]==s[i]:
                        dp[i][j]=1
                        if max_length<(i-j+1):
                            max_length = i-j+1
                            maxx=i
                            maxy=j 
        return s[maxy:maxx+1]
20300