C++ 計算n天后的日期

#include <iostream>

class CDate {
private:
    int m_nDay; // Range: 1 - 30 (lets assume all months have 30 days!)
    int m_nMonth; // Range: 1 - 12
    int m_nYear;

void AddDays(int nDaysToAdd) {
    m_nDay += nDaysToAdd;

    if (m_nDay > 30) {
        AddMonths(m_nDay / 30);

        m_nDay %= 30; // rollover 30th -> 1st
    }
}

void AddMonths(int nMonthsToAdd) {
    m_nMonth += nMonthsToAdd;

    if (m_nMonth > 12) {
        AddYears(m_nMonth / 12);

        m_nMonth %= 12; // rollover dec -> jan
    }
}

void AddYears(int m_nYearsToAdd) {
    m_nYear += m_nYearsToAdd;
}


public:

// Constructor that initializes the object to a day, month and year
CDate(int nDay, int nMonth, int nYear) :
        m_nDay(nDay), m_nMonth(nMonth), m_nYear(nYear) {
}
;

CDate operator +(int nDaysToAdd) {
    CDate newDate(m_nDay, m_nMonth, m_nYear);
    newDate.AddDays(nDaysToAdd);

    return newDate;
}

void DisplayDate() {
    std::cout << m_nDay << " / " << m_nMonth << " / " << m_nYear;
}

};
int main() {
    // Instantiate and initialize a date object to 25 May 2008
    CDate mDate(25, 6, 2008);

std::cout << "The date object is initialized to: ";

// Display initial date
mDate.DisplayDate();
std::cout << std::endl;

std::cout << "Date after adding 10 days is: ";

// Adding 10 (days)...
CDate datePlus10(mDate + 10);

datePlus10.DisplayDate();

return 0;

}
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