题解 | #最长回文子串#

import java.util.*;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            char[] arr = in.nextLine().toCharArray();
            //以i或者(i,i+1)位置的节点为中间节点，向两边辐射
            int max = 0;
            for(int i = 0; i < arr.length; i++){
                int k = i;
                int j = i + 1; // ABA型
                if(i+1 < arr.length && arr[i] == arr[i+1]){
                    j = i + 2; //ABBA型
                }
                while(i > 0 && j < arr.length && arr[i-1] == arr[j]){
                    i--;
                    j++;
                }   
                max = Math.max(max, j - i);
                i = k;
            }
            System.out.println(max);
        }
    }
}