C语言用if或者switch语法求解

代码如下，如有帮助，请采纳一下，谢谢。

#include <stdio.h>

int main()
{
	int year,mon,day;
	int i;
	int nmb = 0;
	scanf("%d %d %d",&year,&mon,&day);
	for (i = 1; i < mon;i++)
	{
		switch(i)
		{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:
			nmb += 31;
			break;
		case 4:
		case 6:
		case 9:
		case 11:
			nmb += 30;
			break;
		case 2:
			if (year % 4 == 0 && year %100 != 0 ||year % 400 == 0)
				nmb += 29;
			else
				nmb += 28;
			break;
		}
		
	}
	nmb += day;
	printf("%d年%d月%d日是该年的第%d天\n",year,mon,day,nmb);
	return 0;
}