程序代码：

#include <stdio.h>
int Sum(int a[], int n);

int main()
{
    int i,n;
    int sum = 0;
    float aver = 0.0;
    printf("Please Inout n 值："); 
    scanf("%d",&n);
    int a[n];
    printf("Please Inout 成绩："); 
    for(i = 0;i < n; i++)
    {
        scanf("%d",&a[i]);
    }
    sum = Sum(a,n);
    aver = (float)sum/n;
    printf("%lf\n",aver);
    return 0;
}

int Sum(int a[], int n)  
{  
     return n == 0?0 : Sum(a, n -1) + a[n -1];  
}