题解 | 牛牛的数学作业

#include <stdio.h>
#include<math.h>
int main() {
    int t;
    scanf("%d", &t);//处理t组数据
    while (t--) {
        int n;
        scanf("%d", &n);//每组有n个数据
        int arr[n];
        scanf("%d", &arr[0]);
        int M = arr[0], m = arr[0];//最大最小值如果设置成0，最大值不会有问题但是最小值会永远是0；
	  //也可用M=INT_MIN;n=INT_MAX,但是要包含头文件<limits.h>
        long long sum = arr[0];
        for (int i = 1; i < n; i++) {
            scanf("%d", &arr[i]);
            if (arr[i] > M)M = arr[i];
            if (arr[i] < m)m = arr[i];
            sum += arr[i];
        }
        printf("%d ", M - m);
        double average =(double) sum / n;
        long double sq = 0.0;
        for (int i = 0; i < n; i++) {
            double diff=arr[i] - average;
            sq += diff*diff;
        }
        double ret = sq / n;
        printf("%.3f\n", ret);
    }
    return 0;
}