题解 | #计算日期到天数转换#

写一个日期类就可以了，不过我这个日期类没写全，够用就行

#include <iostream>
using namespace std;
class Date
{
public:
    Date(int year = 0, int month = 0, int day = 0)
    {
        _year = year;
        _month = month;
        _day = day;
    }
    bool operator>(const Date& d) const
    {
        if(this->_year > d._year)
            return true;
        else if(this->_year == d._year && this->_month > d._month)
            return true;
        else if(this->_year == d._year && this->_month == d._month && this->_day > d._day)
            return true;
        else
            return false;
    }
    bool operator==(const Date& d) const
    {
        if(this->_year == d._year
        && this->_month == d._month
        && this->_day == d._day)
            return true;
        else
            return false;
    }
    bool operator!=(const Date& d) const
    {
        return !(*this == d);
    }
    bool operator<(const Date& d) const
    {
        return !(*this > d || *this == d);
    }
    Date& operator-=(int day)
    {
        if(day < 0)
        {
            *this += -day;
            return *this;
        }
        _day -= day;
        while(_day <= 0)
        {
            _month--;
            if(_month == 0)
            {
                _month = 12;
                _year--;
            }
            _day += GetMonthDays(_year, _month);
        }
        return *this;
    }
    Date& operator+=(int day)
    {
        if(day < 0)
        {
            *this -= -day;
            return *this;
        }
        _day += day;
        while(_day > GetMonthDays(_year, _month))
        {
            _day -= GetMonthDays(_year, _month);
            _month++;
            if(_month == 13)
            {
                _month = 1;
                _year++;
            }
        }
        return *this;
    }
    int GetMonthDays(int year, int month)
    {
        static int monthDays[13]{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        if(month == 2 && ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0))
            return 29;
        else
            return monthDays[month];
    }
    Date& operator++()
    {
        *this += 1;
        return *this;
    }
    int operator-(const Date& d) const
    {
        Date max = *this;
        Date min = d;
        int flag = 1;
        int cnt = 0;
        if(*this < d)
        {
            max = d;
            min = *this;
            flag = -1;
        }
        while(min != max)
        {
            ++cnt;
            ++min;
        }
        return cnt * flag;
    }
    int TheDayOfYear()
    {
        return (*this - Date(_year, 1, 1)) + 1;
    }
private:
    int _year;
    int _month;
    int _day;
};

int main() 
{
    int year, month, day;
    while (cin >> year >> month >> day) 
    { 
        Date d(year, month, day);
        cout << d.TheDayOfYear() << endl;
    }
    return 0;
}