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"

class Solution {
    int sta =0;
    int max = 0;
    public String longestPalindrome(String s) {
        
        if(s.length()<2) return s;
        for(int i=0;i<s.length();i++){
            check(s,i,i);
            check(s,i,i+1);
        }
        return s.substring(sta,sta+max);
        
    }
    public void check(String s,int left,int right){
 

//       從字串中間向兩邊擴充套件，搜尋迴文

      while(left>=0 && right<s.length() && s.charAt(left) == s.charAt(right)){
            left--;
            right++;
        }
        if(max <right - left -1){
            sta = left+1;
            max = right -left -1;
        }
    }
}