<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 {
public:
    string spread(string s,int l,int r){
        while(l >= 0 && r < s.length() && s[l] == s[r]){
            l--;
            r++;
        }
        return s.substr(l+1,r-l-1);
    }
    string longestPalindrome(string s){
        string res;
        for(int i = 0;i < s.length();i++){
            string odd = spread(s,i,i);
            string even = spread(s,i,i+1);
            if(odd.length() < even.length()){
                odd = even;
            }
            if(res.length() < odd.length()){
                res = odd;
            }
            if(res == s) return s;
        }
        return res;
    }
};
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