题解 | 牛牛的数学作业

import java.util.Scanner;
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);
        ArrayList<Integer> arrayList = new ArrayList<>();
        int n = in.nextInt();
        for (int i = 0; i < n; i++) {
            int len = in.nextInt();
            for (int j = 0; j < len; j++) {
                arrayList.add(in.nextInt());
            }
            Integer max = Collections.max(arrayList);
            Integer min = Collections.min(arrayList);
            double sum = 0;
            for (Integer integer : arrayList) {
                sum += integer;
            }
            double average = sum / (double)len;
            double variance = 0;
            for (Integer integer : arrayList) {
                variance += Math.pow(integer - average, 2);
            }
            variance/=len;
            System.out.printf("%d %.3f\n", max - min, variance);
            arrayList.clear();
        }
    }
}