<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 {
    int **d;
public:
    string longestPalindrome(string s) {
        int n = s.length();
        int i,m;
        d = new int*[n];
        int a,b;
        for (i = 0; i < n; ++i){
           d[i] = new int[n];
           memset(d[i], 0, n*sizeof(int));
        }
        for (i = 0; i < n; ++i) {
            d[i][i] = 1;
        }
        a = b = 0;
        for (i = 1; i < n; ++i) {
            if (s[i-1] == s[i]){
                 d[i-1][i] = 1;
                 a = i-1;
                 b = i;
            }
        }
        for (m = 2; m < n; ++m) {
            for (i = 0; i < n-m; ++i) {
                int j = i+m;
                if (s[i] == s[j] && d[i+1][j-1]){
                    d[i][j] = 1;
                    a = i;
                    b = j;
                }
            }
        }
        return s.substr(a,b-a+1);
    }

};
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