程序代码：

#include<stdio.h>

struct a
{
    int x;
    int y;
    int z;
}date;

int main()
{
    int days();

    printf("input:year month day\n");
    scanf("%d%d%d",&date.x,&date.y,&date.z);
    printf("is the%dth\n",days());

    return 1;
}

int days()
{
    int i = 0;

    switch(date.y)
    {
        case 1:i = date.z;break;
        case 2:i = date.z+31;break;
        case 3:i = date.z+59;break;
        case 4:i = date.z+90;break;
        case 5:i = date.z+120;break;
        case 6:i = date.z+151;break;
        case 7:i = date.z+181;break;
        case 8:i = date.z+212;break;
        case 9:i = date.z+243;break;
        case 10:i = date.z+273;break;
        case 11:i = date.z+304;break;
        case 12:i = date.z+334;break;
    }
    if((date.x%4==0&&date.x%100!=0||date.x%400==0)&&date.y>=3)
        i += 1;

    return i;
}