<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) {
        if (s.size() <= 1) 
            return s;
        
        string ans = "";
        for (int i = 0; i < s.size(); i++) {
            string pal = checkBack(s.substr(i));
            if (pal.size() > ans.size()) {
                ans = pal;
            }
        }

        return ans;
    }

    string checkBack(string s) {
        for (int i = 0; i < s.size(); i++) {
            if (s[0] == s[s.size()-i-1] && isPalendrome(s.substr(0, s.size()-i)))
                return s.substr(0, s.size()-i);
        }
        return "";
    }

    bool isPalendrome(string s) {
        for (int i = 0; i < s.size()/2; i++) {
            if (s[i] != s[s.size()-i-1])
                return false;
        }
        return true;
    }
};
416121