题解 | 宝石手串

import java.util.HashMap;
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
        int m = Integer.parseInt(in.nextLine());
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            int n = Integer.parseInt(in.nextLine());
            String s = in.nextLine();
            s = s + s;

            int min = n - 1;
            HashMap<Character, Integer> map = new HashMap<>();
            for (int i=0;i<s.length();i++) {
                char c = s.charAt(i);
                if (map.get(c) != null) {
                    min = Math.min(min, i - map.get(c) - 1);
                }
                map.put(c, i);
            }
            if (min == n - 1) {
                min = -1;
            }            

            System.out.println(min);
        }
    }
}