c语言初学者，来个朋友求解答。

#include<stdio.h>
#include<stdlib.h>

int main () {
   int num;
   int sum = 0;

   scanf("%d", &num);
   int *grades = malloc(num * sizeof(int));
   for (int i = 0; i < num; i++) {
      scanf("%d", &grades[i]);
    }
    for (int i = 0; i < num; i++) {
      sum += grades[i];
    }
    printf("%d", sum / num);
    free(grades);
    return 0;
}

#include <stdio.h>
int main()
{
    int *a = NULL;
    int n,sum=0,i;
    scanf("%d",&n);
    a = (int*)malloc(sizeof(int)*n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
        sum += a[i];
    }
    printf("%g",sum*1.0/n);
    free(a);
    return 0;
}