计算该日是该年的第几天

int leap(int year);

int main(void)
{
 　　int day,month,year,days;
 　　printf("Please input date: ");
 　　printf("year-month-day ");
 　　scanf("%d-%d-%d",&year,&month,&day);
 　　days=sumday(month,day);
　　 if(leap(year)&&month>=3)//是闰年，且超过三月
 　　　　 days=days+1;
　　printf("%d-%d-%d is the %dth day in this year. ",year,month,day,days);
 　　return 0;
}
int leap(int year)
{
 　　int leap=0;
 　　if(year%4==0&&year/100!=0||year%400==0)
  　　　　leap=1;//是闰年返回1
 　　return leap;
}
int sumday(int month,int day)
{
 　　int day_table[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
 　　for(int i=1;i<month;i++)
  　　　　day+=day_table[i];
 　　return day;
}

运行结果：