Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000. Example 1: Input: "babad" Output: "bab" Note: "aba" is also a valid answer. Example 2: Input: "cbbd" Output: "bb" The performance is pretty good, surprisingly. public class Solution { private int lo, maxLen; public String longestPalindrome(String s) { int len = s.length(); if (len < 2) return s; for (int i = 0; i < len-1; i++) { extendPalindrome(s, i, i); //assume odd length, try to extend Palindrome as possible extendPalindrome(s, i, i+1); //assume even length. } return s.substring(lo, lo + maxLen); } private void extendPalindrome(String s, int j, int k) { while (j >= 0 && k < s.length() && s.charAt(j) == s.charAt(k)) { j--; k++; } if (maxLen < k - j - 1) { lo = j + 1; maxLen = k - j - 1; } }}