题目要求输入一行整数直到输入0，然后计算奇数和偶数(0除外)的个数以及求出它们的平均值。
#include<stdio.h>
int main(void)
{
    int a;
    int n_even = 0;
    int n_odd = 0;
    int sum_even = 0;
    int sum_odd = 0;
    float average_even;
    float average_odd;
   
    while(scanf("%d",&a)==1)
    {
   
        if((a%2)==0 && a!='0')
        {
            
          n_even++;
          sum_even+=a;
        }  
          else
          {
            n_odd++;
            sum_odd+=a;
          }
            
        
    }
    average_even=sum_even/n_even;
    average_odd=sum_odd/n_odd;
    printf("there are %d even number,%d odd number.\n",n_even,n_odd);
    printf("the average of all even numbers is %.1f.\n",average_even);
    printf("the average of all odd numbers is %.1f.\n",average_odd);
    return 0;
}

while里加一句if(a==0) break;

while(scanf("%d",&a)!=0)

其实感觉分开写比较好，  scanf("%d",&a);
while(a!=0)

#include <stdio.h>

int main( void )
{
    unsigned n_even=0, n_odd=0;
    unsigned sum_even=0, sum_odd=0;
    for( int val; scanf("%d",&val)==1 && val!=0; )
    {
        if( val%2==0 )
        {
            sum_even += val;
            ++n_even;
        }
        else
        {
            sum_odd += val;
            ++n_odd;
        }
    }
    printf( "there are %u even numbers, %u odd numbers.\n", n_even, n_odd );
    printf( "the average of all even numbers is %g.\n", n_even!=0 ? sum_even*1.0/n_even : 0.0 );
    printf( "the average of all odd numbers is %g.\n", n_odd!=0 ? sum_odd*1.0/n_odd : 0.0 );
}

这么写是不对的。scanf()的返回值是读入的复合格式要求的字符的个数，不是读入的字符的值。

scanf()原型是int scanf (const char*, ...);