题解 | 牛牛的数学作业

#include <stdio.h>
#include<math.h>
int main() {
    int t;
    scanf("%d", &t);
    while (t--) {
        int n;
        scanf("%d", &n);
        int a[n];
        int max = -1000000000, min = 1000000000, sum = 0;
        for (int j = 0; j < n; j++) {
            scanf("%d", &a[j]);
            if (a[j] > max) max = a[j];
            if (a[j] < min) min = a[j];
            sum += a[j];
        }
        double mean = (double)sum / n;
        double variance = 0.0;
        for (int k = 0; k < n; k++) {
            variance += (a[k] - mean) * (a[k] - mean);
        }
        variance /= n;
        printf("%d %.3f\n", max - min, variance);
    }
    return 0;
}