判断闰年，根据输入的年月输出这个月的天数，根据输入的年月日输出这一年1月1日到month-day有多少天

 采用的方法是“哨兵位”，浪费了一个空间

int Is_leap_year(int year)
{
	if(year < 1)
	{
		return -1;
	}

	return (0 ==year % 4 && 0 != year % 100)||(0 == year % 400);//是闰年
}

int Get_month_day(int year,int month)
{
	if(month < 1 || month > 12 || -1 == Is_leap_year(year))
	{
		printf("Get_month_day:error month\n");
		return 0;
	}	
	
	int day_month[13]={29,31,28,31,30,31,30,31,31,30,31,30,31};
	if(Is_leap_year(year) && month == 2)
	{
		month = 0;
	}
	
	return day_month[month];	
}


int Get_total_day(int year,int month,int day)
{
	if(Get_month_day(year,month) == 0 ||  day < 1 || day > Get_month_day(year,month))
	{
		printf("Get_total_day:error data\n");
		return -1;
	}

	int total[13]={0,0,31,59,90,120,151,181,212,243,273,304,334};
	int sum = 0;

	sum = total[month] + day;

	if(month > 2 && Is_leap_year(year))
	{
		sum++;
	}
	
	return sum;
}

int main()
{
	int year = 0;
	int month = 0;
	int day = 0;
	printf("input year,month,day:");
	scanf("%d %d %d",&year,&month,&day);
	
	if(Is_leap_year(year) == -1)
	{
		printf("error year\n"); 
	}
	else if(Is_leap_year(year) == 0)
	{
		printf("not leap year\n");
	}
	else
	{
		int month_day = Get_month_day(year,month);
		if(month_day > 0)
		{
			printf("day is %d\n",month_day);
			int total = Get_total_day(year,month,day);
			if(total != -1)
			{
				printf("total is %d\n",total);
			}
		}
	}
	
	return 0;
}

代码已经在VS-2012说明通过测试