程序代码：

#include<stdio.h>
int main()
{
    float a,b,ave;
    int n,i;
    a=0;
    scanf("%d\n",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%f ",&b);
        a+=b;
    }
    ave=a/n;
    printf("%.2f\n",ave);
return 0;    
}
[local]1[/local]

程序代码：

#include<stdio.h>
int main()
{
    float a=0,b,ave;    // a 没有赋初值，输出结果存在不确定性
    int n,i;
    a=0;
    scanf("%d",&n);     // 多了一个换行符，有残留给第一个 b 值的可能
    for(i=1;i<=n;i++)
    {
        scanf("%f",&b);
        a+=b;
    }
    ave=a/n;
    printf("%.2f\n",ave);
return 0;   
}

[此贴子已经被作者于2020-10-24 20:08编辑过]

程序代码：

#include<stdio.h>
int main()
{
    int m,e,choice1;
    char choice2;
    double a,cost;
    printf("Enter how much gas a = ");
    scanf("%lf",&a);
    printf("90# gas seclet 90\n");
    printf("93# gas select 93\n");
    printf("97# gas select 97\n");
    printf("Enter choice1:");
    scanf("%d",&choice1);
        
    switch(choice1)
    {
    case 90#:cost=6.95 * a;break;
    case 93#:cost=7.44 * a;break;
    case 97#:cost=7.93 * a;break;
    default:cost=0.00;break;
    }
   
    printf("self-service select m\n");
    printf("ancillary-service select e\n");
    printf("Enter choice2:");
    scanf("%c",&choice2);

    if(choice2 == 'm')
    {
        cost=cost * (1-0.05);
    }
    else if(choice2 == 'e')
    {
        cost=cost * (1-0.03);
    }
    else
        printf("\n");
        printf("You need pay %.2f yuan\n",cost);
    return 0;
}