http://leetcode.com/onlinejudge#question_5

LongestPalindromO(n^2).java

public class Solution {
    public String longestPalindrome(String s) {
        // Start typing your Java solution below
        // DO NOT write main() function
        String longest = "";
        for(int i = 0; i < s.length(); i++) {
            int j;
            // pivot at a char
            for(j = 1; i - j >=0 && i + j < s.length(); j++) {
                if(s.charAt(i - j) != s.charAt(i + j)) {
                    break;
                }
            }
            String palindrom = s.substring(i-j+1, i+j);
            if(palindrom.length() > longest.length()) {
                longest = palindrom;
            }
            // pivot between two chars
            for(j = 0; i - j >= 0 && i + j + 1 < s.length(); j++) {
                if(s.charAt(i - j) != s.charAt(i + j + 1)) {
                    break;
                }                
            }
            palindrom = s.substring(i - j + 1, i + j + 1);
            if(palindrom.length() > longest.length()) {
                longest = palindrom;
            }
        }
        return longest;
    }
}