Leetcode_005_Longest_Palindromic_Substring

public class Solution {    public String longestPalindrome(String s) {        String result = "";        if(s.length() == 1) return s;        for(int i = 0; i<s.length()-1; i++){            String odd = helper(i,i,s);            String even = helper(i,i+1,s);            if(odd.length()>even.length()){                if(odd.length() > result.length()) result = odd;            }else{                if(even.length() > result.length()) result = even;            }        }        return result;    }        private String helper(int i, int j, String s){        if(i != j && s.charAt(i) != s.charAt(j)){            return "";        }        while(i-1>=0 && j+1<s.length() && s.charAt(i-1) == s.charAt(j+1)){            i--;            j++;        }        return s.substring(i,j+1);    }}

go through while string, make every character possible middle character(odd or even) and search for max length.