题解 | #计算日期到天数转换# - 写写日期类

#include <iostream>

using namespace std;

class Date
{
    friend istream& operator>>(istream& in, Date& d);
public:
    Date(int year, int month = 1, int day = 1)
    {
        _year = year;
        _month = month;
        _day = day;
    }
    int GetMonthDay(int year, int month) const {
        static int monthDayArr[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        int day = monthDayArr[month];
        if (month == 2 && ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))) {
            day += 1;
        }
        return day;
    }
    bool operator!=(const Date& d) const {
        return (_year != d._year) || (_month != d._month) || (_day != d._day);
    }
    Date& operator+=(int day) {
        _day += day;
        while (_day > GetMonthDay(_year, _month)) {
            _day -= GetMonthDay(_year, _month);
            _month++;
            if (_month == 13) {
                _year++;
                _month = 1;
            }
        }
        return *this;
    }
    Date& operator++() {
        *this += 1;
        return *this;
    }
    int operator-(const Date& d)
    {
        // *this 大，d 为小
        Date max = *this, min = d;
        int cnt = 1;
        while (max != min)
        {
            ++min;
            ++cnt;
        }
        return cnt;
    }
public:
    int _year;
private:
    int _month;
    int _day;
};

istream& operator>>(istream& in, Date& d)
{
    in >> d._year >> d._month >> d._day;
    return in;
}

int main()
{
    Date d1(1); // 输入
    cin >> d1;

    Date d2(d1._year);

    cout << (d1 - d2) << endl;
}