写出来但达不到应该出现的功能，因为是刚学后面调用子函数的那段不知道该怎么写

include <stdio.h>

void main ()
{
int day, month,year,yearday; //定义代表日、月、年和天数的变量
void month_day(int year,int month,int day,int *yearday); //声明函数
printf ("输入年 月 日： "); //提示输入数据：年和天数
scanf ("%d%d%d", &year,&month,&day );
month_day (year,month,day,&yearday ); // 调用计算月、日函数
printf ("是该年第%d天\n",yearday);
}

void month_day(int year,int month,int day,int *yearday)
{
int i,s,k;
int tab [2][12]= {
   {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
   {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
            };                                // 定义数组存放非闰年和闰年每个月的天数
s=(year%4==0 && year% 100!= 0 || year%400==0);
for ( i=0;i<month-1; i++)
{
       yearday+=tab[s][i];
}
yearday+=day;
}

首先代码有问题，最后一个参数是指针，最后几行用这个参数的时候，得用*yearday += tab[s][i]; *yearday += day;
调用函数如下：

#include <stdio.h>
int main()
{
  int year,month,day;
  int yearday = 0;
  scanf("%d%d%d",&year,&month,&day);
  month_day(year,month,day,&yearday);
  printf("%d",yearday);
  return 0;
}

int month_day(int year,int month,int day)
{
int i,s,k, yearday=0;
int tab [2][12]= {
   {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
   {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
            };                                // 定义数组存放非闰年和闰年每个月的天数
s=(year%4==0 && year% 100!= 0 || year%400==0);
for ( i=0;i<month-1; i++)
{
       yearday+=tab[s][i];
}
yearday+=day;
return yearday;
}