Longest Palindromic Substring

 1 class Solution {
 2 public:
 3     string longestPalindrome( string s ) {
 4         if( s.empty() ) { return string( "" ); }
 5         int slen = s.length(), curlen = 1, ii = 0;
 6         bool isPalindrome[2][1000];
 7         for( int step = 1; step < slen; ++step ) {
 8             for( int i = 0; i <= slen-step; ++i ) {
 9                 int cur = (step-1) % 2;
10                 if( step <= 2 ) {
11                     isPalindrome[cur][i] = s[i] == s[i+step];
12                 } else {
13                     isPalindrome[cur][i] = s[i] == s[i+step] && isPalindrome[cur][i+1];
14                 }
15                 if( curlen < step+1 && isPalindrome[cur][i] ) {
16                     ii = i;
17                     curlen = step+1;
18                 }
19             }
20         }
21         return s.substr( ii, curlen );
22     }
23 };