输入某年某月某日，并判断是一年中的第几天

#include<stdio.h>

int main()
{
int year, month, day, sum, add;
printf("\n请输入年月日");
scanf_s("%d,%d,%d", &year, &month, &day);
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; break;
default:
printf("输入错误，重新输入"); break;
}
sum = sum + day;
if (year % 400 0 || (year % 4 0 && year % 100 != 0))

{
add = 1;
}
else {
add = 0;
}
if (add == 1 && month > 2)
{
sum = sum + 1;
}
printf("这是一年中的第 %d天。", sum);
return 0;
}