为什么这样错了
#include <stdio.h>
int main()
{
/* 定义需要计算的日期 */
int year = 2008;
int month = 8;
int day = 8;
switch(month)
{
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;
default:
printf("YSNB");
break;
}
sum +=day;
if(year%400==0||(year%4==0&&year%100!=0))
{
sum==sum;
}
else
{
sum +=1;
}
printf("是该年中的第%d天",sum);
return 0;
}