题解 | 牛牛的数学作业

import java.util.*;


// 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 T = in.nextInt();
        

        for(int i =0; i<T ; i++){
            List<Integer> list = new ArrayList<>();
            int sum = 0;
            int n = in.nextInt();
            
            for(int j =0; j< n; j++){
                int a = in.nextInt();
                list.add(a);
                sum += a;
            }
            System.out.print(Collections.max(list)-Collections.min(list)+" ");
            double b = (double)sum/n;
            double sumavg = 0;

            for(int k=0; k<list.size(); k++){
                sumavg += Math.pow(list.get(k)-b,2);
            }
            System.out.println(String.format("%.3f", sumavg/n));

            
            
        }
    }
}