题解 | #日期累加#

C++方法 实现一个日期类的累加，返回相加后的日期结果，那就必须对日期类的+运算符做重载。 重载方法如下：

Date Date::operator+(int n)
{
	int year = _year;
	int month = _month;
	int day = _day;
	int days = GetMonthDay(year, month);

	while (day + n > days)
	{
		month++;
		if (month > 12)
		{
			year++;
			month = 1;
		}
		n -= days;
		days = GetMonthDay(year, month);//取每月天数
	}
	day += n;
	return Date(year, month, day);
}

然后我们对输出运算符做重载，便于输出，重载时要注意，输出运算符最好重载为友元函数，并且我们根据输出要求，不满10的月份和年份前添加0.代码如下

ostream& operator<<(ostream& out, const Date& d)
{
    if(d._month<10&&d._day<10)
        out << d._year << "-" <<0<< d._month << "-" <<0<< d._day;
    else if(d._month>=10&&d._day<10)
        out << d._year << "-" << d._month << "-" <<0<< d._day;
    else if(d._month<10&&d._day>=10)
        out << d._year << "-" <<0<< d._month << "-" << d._day;
    else
        out << d._year << "-" << d._month << "-" << d._day;
    return out;
}

在主函数输入时要注意是循环输入

	for(int cur=0;cur<count;cur++)
    {
        cin>>year>>month>>day>>n;
        Date d(year,month,day);
        Date d1=d+n;
        cout<<d1<<endl;
	}

完整代码如下:

#include<iostream>
using namespace std;
class Date
{
protected:
	friend ostream& operator<<(ostream& out, const Date& d);
public:
    Date(int year,int month,int day);
    Date operator+(int n);
    int GetMonthDay(int year, int month);
private:
    int _year;
    int _month;
    int _day;
};

Date::Date(int year,int month,int day)
{
    _day=day;
    _month=month;
    _year=year;
}
ostream& operator<<(ostream& out, const Date& d)
{
    if(d._month<10&&d._day<10)
        out << d._year << "-" <<0<< d._month << "-" <<0<< d._day;
    else if(d._month>=10&&d._day<10)
        out << d._year << "-" << d._month << "-" <<0<< d._day;
    else if(d._month<10&&d._day>=10)
        out << d._year << "-" <<0<< d._month << "-" << d._day;
    else
        out << d._year << "-" << d._month << "-" << d._day;
    return out;
}
Date Date::operator+(int n)
{
	int year = _year;
	int month = _month;
	int day = _day;
	int days = GetMonthDay(year, month);

	while (day + n > days)
	{
		month++;
		if (month > 12)
		{
			year++;
			month = 1;
		}
		n -= days;
		days = GetMonthDay(year, month);
	}
	day += n;
	return Date(year, month, day);
}

int Date::GetMonthDay(int year, int month)
{
    static int days[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
	int day = days[month];
	if (month == 2 && ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)))
	{
		day += 1;
	}
	return day;
}

int main()
{
    
    int count=0;
    int year=0,month=0,day=0;
    int n=0;
     cin>>count;
    for(int cur=0;cur<count;cur++)
    {
        cin>>year>>month>>day>>n;
        Date d(year,month,day);
        Date d1=d+n;
        cout<<d1<<endl;
}

    
    return 0;
}