一些日期计算

给定日期和星期几求另一个日期是星期几

容斥

#include<cstdio>
using namespace std;
int days[14]={0,31,28,31,30,31,30,31,31,30,31,30,31,0};
int dayRest[14],dayBegin[14];
struct Date{
	int year,month,day;
	Date(int y,int m,int d):year(y),month(m),day(d){
	}
	bool is29days() const{
		if(year%100) return !(year%4);
		return !(year%400);
	}
	static bool is29days(int y){
		if(y%100) return !(y%4);
		return !(y%400);
	}
	int dayOfRest() const{
		if(month>2||!is29days())
			return dayRest[month]-day;
		return dayRest[month]-day+1;
	}
	int dayOfBegin() const{
		if(is29days()) return 366-dayOfRest();
		return 365-dayOfRest();
		if(month<=2||!is29days())
			return dayBegin[month-1]+day;
		return dayBegin[month-1]+day+1;
	}
	void print(){
		printf("%d-%d-%d\n",year,month,day);
	}
	static int dayOfYear(int year){
		return year*365+year/4-year/100+year/400;
	}
	static int dayOfYear(int yearBegin,int yearEnd){
		return dayOfYear(yearEnd)-dayOfYear(yearBegin-1);
		int day=0;
		for(int i=yearBegin;i<=yearEnd;++i)
			if(is29days(i)) day+=366;
			else day+=365;
		return day;
	}
	friend bool operator <(const Date d1,const Date d2){
		if(d1.year!=d2.year) return d1.year<d2.year;
		if(d1.month!=d2.month) return d1.month<d2.month;
		if(d1.day!=d2.day) return d1.day<d2.day;
	}
	friend bool operator >(Date d1,Date d2){
		return d2<d1;
	}
	friend int operator -(const Date d2,const Date d1){//d2-d1
		if(d1<d2){//[d1,d2]
			if(d1.year==d2.year){
				return d2.dayOfBegin()-d1.dayOfBegin();
			}
			int day=d1.dayOfRest()+d2.dayOfBegin();
			day+=dayOfYear(d1.year+1,d2.year-1);
			return day;
		}
		return -(d1-d2);
	}
};
int dayofweek(Date d1,int day1,Date d2){
	int day2=(day1+(d2-d1)%7+7)%7;
	if(!day2) day2=7;
	return day2;
} 
int main(){
	for(int i=1;i<=12;++i){
		dayBegin[i]=dayRest[i]=days[i];
	}
	for(int i=2;i<=12;++i)
		dayBegin[i]+=dayBegin[i-1];
	for(int i=11;i>=1;--i)
		dayRest[i]+=dayRest[i+1];
//	printf("%d\n",dayofweek(Date(1999,12,25),6,Date(2022,2,20)));
	printf("%d\n",dayofweek(Date(2021,12,25),6,Date(2022,2,28)));
	return 0;
}