c语言编程 （要求正确简明）给出年,月,日,计算该日是该年的第几天?

#include
"stdio.h"
#include
"conio.h"
main()
{

int
day,month,year,sum,leap;

printf("\nplease
input
year,month,day\n");

scanf("%d%d%d",&year,&month,&day);

switch(month)
/*先计算某月以前月份的总天数*/

{

case
1:sum=0;break;

case
2:sum=31;break;

case
3:sum=59;break;

case
4:sum=90;break;

case
5:sum=120;break;

case
6:sum=151;break;

case
7:sum=181;break;

case
8:sum=212;break;

case
9:sum=243;break;

case
10:sum=273;break;

case
11:sum=304;break;

case
12:sum=334;break;

default:printf("data
error");break;

}

sum=sum+day;
/*再加上某天的天数*/

if(year%400==0||(year%4==0&&year%100!=0))
/*判断是不是闰年*/

leap=1;

else

leap=0;

if(leap==1&&month>2)
/*如果是闰年且月份大于2,总天数应该加一天*/

sum++;

printf("It
is
the
%dth
day.",sum);
}