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 sc  = new Scanner(System.in);
            StringBuilder strBuilder = new StringBuilder(sc.nextLine());
            char[] chars = strBuilder.toString().toCharArray();
            Integer strLength[] = new Integer[chars.length];
            for (int i = 0; i < chars.length; i++) {
                strLength[i] = 1;//先赋值，避免空值。
                for (int j = i+1; j < chars.length; j++) {
                    if(chars[i]==chars[j]){
                        Integer left = i ;
                        Integer right = j ;//不改变i和j
                        Boolean flag = true;
                        while (flag==true){
                            left++;
                            right--;

                            if(chars[left]!=chars[right]){
                                flag = false;
                            }else {
                                flag = true;
                            }

                            if(left == right || left > right){//奇数or偶数
                                break;
                            }
                        }
                        if(flag == true){//说明一直都相等对称
                            strLength[i] = j - i + 1;
                        }
                    }
                }
                if(i!=0) {//i=0,i-1等于-1会出界
                    strLength[i] = Math.max(strLength[i], strLength[i - 1]);
                }
            }
            System.out.println(strLength[strLength.length - 1]);
        }
}