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);
        while (in.hasNext()) {
            String str = in.nextLine();
            int desLen = 0;
            for (int i = 0; i < str.length(); i++) {
                //ABA类型
                int len1 = getLongest(str, i, i);
                //ABBA类型
                int len2 = getLongest(str, i, i + 1);
                desLen = Math.max(desLen, Math.max(len1, len2));
            }
            System.out.println(desLen);
        }
    }

    public static int getLongest(String str, int left, int right) {
        //从中心点向两端扩散
        while (left >= 0 && right < str.length() &&str.charAt(left) == str.charAt(right)) {
            left--;
            right++;
        }
        return right - left - 1;
    }
}