<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 longestPalindrome(string s) {
        int l = s.length();

        if(l <= 1) return s;

        string ans = "";
        ans += s[0];

        for(int i = 0; i < l; ++i) {
            string cur = "";
            for(int j = 1; i-j >= 0 && i+j < l; ++j) {
                if(s[i-j] == s[i+j]) {
                    cur += s[i+j];
                } else {
                    break;
                }
            }

            string rev = cur;
            reverse(rev.begin(), rev.end());
            cur = rev + s[i] + cur;

            if(ans.length() < cur.length()) ans = cur;
            cur = "";

            for(int j = 0; i-j >= 0 && i+j+1 < l; ++j) {
                if(s[i-j] == s[i+j+1]) {
                    cur += s[i+j+1];
                } else {
                    break;
                }
            }

            rev = cur;
            reverse(rev.begin(), rev.end());
            cur = rev + cur;

            if(ans.length() < cur.length()) ans = cur;
        }  
        
        return ans;
    }
};
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