已知1990年1月1号星期1.求出输入的年月日是星期几

参考地址：http://topic.csdn.net/u/20110822/17/ef33b75f-a67c-413d-9b33-9c8dfc34e2f9.html

#include<iostream>
using namespace std;
void main()
{
	//已知1990年1月1号星期1.求出输入的年月日是星期几
	int year,month,day;//年月日
	int num=0,leap,week;
	int sum=0;
	cout<<"请输入年月日"<<endl;
	cin>>year;
	cin>>month;
	cin>>day;
if(year>=1990)//当输入的年大于1990
{
	for(int i=1990;i<year;i++)//计算年的天数
	{
		if((i%4==0&&i%100!=0)||(i%400==0))
			num+=366;
		else
			num+=365;
	}
	if((year%4==0&&year%100!=0)||(year%400==0))
		leap=1;
	else
		leap=0;
	switch(month-1)//计算月的天数
	{
	case 11:
		sum=num+365+leap-31;
		break;
		case 10:
			sum=num+365+leap-31-30;
			break;
		case 9:
			sum=num+365+leap-31-30-31;
			break;
		case 8:
			sum=num+365+leap-31-30-31-30;
			break;
		case 7:
			sum=num+365+leap-31-30-31-30-31;
			break;
		case 6:
			sum=num+365+leap-31-30-31-30-31-31;
			break;
		case 5:
			sum=num+365+leap-31-30-31-30-31-31-30;
			break;
		case 4:
			sum=num+365+leap-31-30-31-30-31-31-30-31;
			break;
		case 3:
			sum=num+365+leap-31-30-31-30-31-31-30-31-30;
			break;
		case 2:
			sum=num+365+leap-31-30-31-30-31-31-30-31-30-31;
			break;
		case 1:
			sum=num+365+leap-31-30-31-30-31-31-30-31-30-31-28-leap;
			break;
		case 0:
			sum=num;
			break;
		default:
			break;
	}
	sum=sum+day-1;//求天数总和
	cout<<"总天数为"<<sum<<"天"<<endl;
	week=sum%7;//求出天数
	if(week!=0)
		cout<<year<<"年"<<month<<"月"<<day<<"日"<<"是星期"<<week+1<<endl;
	else
		cout<<year<<"年"<<month<<"月"<<day<<"日"<<"是星期1"<<endl;
}
else//小于1990 同上
{
	for(int i=year+1;i<1990;i++)
	{
		if((i%4==0&&i%100!=0)||(i%400==0))
			num+=366;
		else
			num+=365;
	}
	if((year%4==0&&year%100!=0)||(year%400==0))
		leap=1;
	else
		leap=0;
	switch(month)
	{
	case 12:
		sum=num;
		break;
	case 11:
		sum=num+31;
		break;
	case 10:
		sum=num+31+30;
		break;
	case 9:
		sum=num+31+30+31;
		break;
	case 8:
		sum=num+31+30+31+30;
		break;
	case 7:
		sum=num+31+30+31+30+31;
		break;
	case 6:
		sum=num+31+30+31+30+31+31;
		break;
	case 5:
		sum=num+31+30+31+30+31+31+30;
		break;
	case 4:
		sum=num+31+30+31+30+31+31+30+31;
		break;
	case 3:
		sum=num+31+30+31+30+31+31+30+31+30;
		break;
	case 2:
		sum=num+31+30+31+30+31+31+30+31+30+31;
		break;
	case 1:
		sum=num+31+30+31+30+31+31+30+31+30+31+28+leap;
		break;
	default:
		break;
	}
	if (month==1||month==3||month==5||month==7||month==8||month==10||month==12)
	{
		sum=sum+31-day+1;
	}
	if(month==4||month==6||month==9||month==11)
	{
		sum=sum+30-day+1;
	}
	if (month==2)
	{
		sum=sum+28+leap-day+1;
	}
	cout<<"总天数为"<<sum<<"天"<<endl;
	week=sum%7;//求出天数
	if(week!=0)
		cout<<year<<"年"<<month<<"月"<<day<<"日"<<"是星期"<<8-week<<endl;
	else
		cout<<year<<"年"<<month<<"月"<<day<<"日"<<"是星期一"<<endl;
}
}