从键盘输入年月日，计算该日是该年的第几天
#include <stdio.h>
void main()
{   
    int year;
    int month;
    int day;
    int days;
    int i,l;
    static int t[][13]={{0,31,28,31,30,31,30,31,31,30,31,30,31},{0,31,29,31,30,31,30,31,31,30,31,30,31}};
l: printf("%d,%d,%d",&year,&month,&day);
   if(year<0||month<1||day>31||month>12)
   {
       printf("error!");
       goto l;
   }
   l=0;
   days=day;
   if(year%4==0&&year%100==0||year%100==0)
    l=1;/*闰年为t[1][13]*/
   i=1;
   while(i<month)
   {
       days+=t[1][i];
       i++;
   }
   printf("days=%d",days);
}