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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            // int a = in.nextInt();
            // int b = in.nextInt();
            // System.out.println(a + b);
            String s = in.nextLine();
            System.out.println(getMax(s));
        }
    }

    private static int getMax(String s) {
        int n = s.length();
        int max = 0;
        for (int i=0;i<n;i++) {
            int l1=i-1, r1=i+1, len1=1;
            len1 = getPerCharMax(s, l1, r1, len1);
            
            int l2=i, r2=i+1, len2=0;
            len2 = getPerCharMax(s, l2, r2, len2);

            max = Math.max(max, len1);
            max = Math.max(max, len2);
        }

        return max;
    }

    private static int getPerCharMax(String s, int l, int r, int len) {
        while (l >= 0 && r < s.length() && s.charAt(l) == s.charAt(r)) {
            len += 2;
            l--;
            r++;
        }
        return len;
    }
}