Longest Palindrome Substring

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example:

Input: "babad"

Output: "bab"

Note: "aba" is also a valid answer.

Example:

Input: "cbbd"

Output: "bb"

Solution

public class Solution {
    public String longestPalindrome(String s) {
        String res = "";
        int currentLength = 0;

        for(int i = 0;i<s.length();i++) {
            if(isPalindrome(s, i - currentLength - 1, i)) {
                res = s.substring(i - currentLength - 1, i + 1);
                currentLength  += 2;
            } else if(isPalindrome(s, i - currentLength, i)) {
                res = s.substring(i - currentLength, i + 1);
                currentLength  += 1;
            }
        }

        return res;
    }

    public boolean isPalindrome(String s, int begin, int end) {
        if(begin < 0 ) return false;

        while(begin < end) {
            if(s.charAt(begin++) != s.charAt(end--)) return false;
        }

        return true;
    }
}