题解 | #密码截取#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        int[] arr = new int[s.length()];
        int[] arr2 = new int[s.length()];

        for(int i = 0; i < s.length(); i++){
            arr[i] = 1;
            arr2[i] = 2;
            for(int j = 1 ; j <= i; j++){
                if(i + j > s.length() - 1){
                    break;
                }
                if(s.charAt(i-j) == s.charAt(i+j)){
                    arr[i] += 2;
                }else{
                    break;
                }
            }


            if(i < s.length() -2 && s.charAt(i) == s.charAt(i + 1)){
                for(int j = 1; j <= i; j++){

                    if(i + 1 + j > s.length() -1){
                        break;
                    }
                    if(s.charAt(i-j) == s.charAt(i+1+j)){
                        arr2[i] += 2;
                    }else{
                        break;
                    }
                }
            }
        }

        int max = arr[0];
        for(int i = 0; i < arr.length; i++){
            max = Math.max(max, arr[i]);
        }

        for(int i = 0; i < arr2.length; i++){
            max = Math.max(max, arr2[i]);
        }


        System.out.println(max);
    }
}