// birthweek.cpp : Defines the entry point for the console application.
//
/*計算生日是星期幾
1、 已知公元1 年1 月1 日是星期一 
2、 算法提示：如果輸入的是2006 年3 月12 日，計算方法是 
(1) 先計算從公元0001 年初（0001-1-1）到2005 年末(2005-12-31)共多少天，注意其中 
有閏年，閏年是366 天，平年是365 天。閏年的判斷條件滿足(見教材例3.8 題)： 
(( year%4==0 && year%100!=0 )!!(year%400==0)) 
(2) 然后再計算2006 年1 月1 日到2006-3-12 是多少天。注意同樣判斷本年度是否閏年， 
即二月份是28 天還是29 天。 
(3) 上述兩部分相加即從公元0001 年初（0001-1-1）到2006 年末(2006-3-12)的天數(shù)， 
用該天數(shù)模7（total%7）即得到星期數(shù)。*/
#include "stdafx.h"
#include "iostream.h"
int leap(int year)
{
	int day;
	if((year%4 == 0 && year % 100 != 0)||(year%4 == 0 && year % 100 == 0))
	{
		day = 366;
	}
	else day = 365;
	return day;
}
int monthday(int month)
{
	int day;
	switch(month)
	{
	case 0:day=0;break;
	case 1:day = 31;break;
	case 3:day = 62;break;
    case 4:day = 92;break;
	case 5:day = 123;break;
	case 6:day = 153;break;
	case 7:day = 184;break;
	case 8:day = 215;break;
    case 9:day = 245;break;
	case 10:day = 276;break;
    case 11: day = 306;break;
	case 12: day = 337;break;
	}
	return day;
}
void week(int n)
{
	switch(n)
	{
	case 1: cout<<"Your birthday is on Monday!";break;
	case 2: cout<<"Your birthday is on Tuseday!";break;
	case 3: cout<<"Your birthday is on Wendsday!";break;
	case 4: cout<<"Your birthday is on Thursday!";break;
	case 5: cout<<"Your birthday is on Friday!";break;
	case 6: cout<<"Your birthday is on Saturday!";break;
	case 0: cout<<"Your birthday is on Sunday!";break;
	}
}
void main()
{
	int year,month,day,day2,i,sum,sum1;
    all:sum=0;
    to:cout<<"please your birthday:";
     cin>>year>>month>>day;
	if((year == 0)||(month == 0)||(month >12)||(day == 0)||(day>31))
	{
		cout<<"Input Error!Please input again!"<<endl;
		goto to;
	}
	if(leap(year)==366) day2 = 29;
	else day2 = 28;
	for(i=2;i<=year;i++)
	{
	    sum+=leap(i-1);
	}
	if(year == 1)
	{
		if(month < 3) sum += monthday(month-1) + day;
	    else sum += monthday(month-1) + day2 + day;
	}
	else
	{
	if(month < 3) sum += monthday(month-1) + day-1;
	else sum += monthday(month-1) + day2 + day-1;
	}
	week(sum%7);
	cout<<endl;
	goto all;
}