题解 | 宝石手串

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);
        int num = in.nextInt();
        for (int i = 0; i < num; i++) {
            int len = in.nextInt();
            String str = in.next();
            // aba aba 模拟首尾连接
            String doubleStr = str + str;
            int tmp = 1;
            boolean flag = false;
            for (int j = 0; j < str.length(); j++) {
                if (doubleStr.charAt(j) == doubleStr.charAt(j + tmp)) {
                    flag = true;
                    break;
                }
                if(j == str.length() - 1 && tmp < str.length() - 1) {
                    j = -1;
                    tmp++;
                }
            }
            System.out.println(flag ? tmp - 1 : -1);
        }
    }
}