输入某年某月末日，判断这一天是这年的第几天

#include <stdio.h>
int main()
{
  int day,month,year,sum,leap;
  printf("please 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*/
{
  case1:sum=0;break;
  case2:sum=31;break;
  case3:sum=59;break;
  case4:sum=90;break;
  case5:sum=120;break;
  case6:sum=151;break;
  case7:sum=181;break;
  case8:sum=212;break;
  case9:sum=243;break;
  case10:sum=273;break;
  case11:sum=304;break;
  case12: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++;