题解 | 日期累加

#include <iostream>
#include <iomanip>
using namespace std;

class Date
{
    public:
        Date(int y = 1,int m = 1, int d = 1)//err 要么全缺省要么无参
        :_y(y),_m(m),_d(d)
        {}
        int Get(int y, int m)const
        {
            static int M[12] = {31,28,31,30,31,30,31,31,30,31,30,31};
            if(m == 2 && (y%4 == 0 && y%100 != 0) || (y%400 == 0) )
                return 29; 
            return M[m-1];
        }
        Date& operator++();
        Date& operator+=(int day);
        int GetY()
        {
            return _y;
        }
        int GetM()
        {
            return _m;
        }
        int GetD()
        {
            return _d;
        }
    private:
    int _y;
    int _m;
    int _d;

};
Date& Date::operator+=(int day) //err Date类名忘加
{
    while(day--)
    {
        // (*this)++;//这是后置++!!
        ++(*this);
    }
    return *this;
}

Date& Date::operator++()
        {
            if(_d + 1 > Get(_y,_m))
            {
                if(_m + 1 > 12)
                {
                    ++_y;
                    _m = 1;
                    _d = 1;
                }
                else
                {
                    ++_m;
                    _d = 1;
                }
            }
            else
            {
                ++_d;
            }
            return *this;
        }
int main() 
{
    int m1, y, m, d;
    cin >> m1;
    int m2 = m1;
    //开数组用于存储结果
    // int* arr = new int[3m1]{0};
    int* arr = new int[3*m1](); //err 3*m1写成了3m1 要想"全部元素初始化为0 就只有()
    int j = 0;
    while(m1--)
    {
        cin >> y >> m >> d;
        int day;
        cin>>day;
        Date D(y,m,d);
        D += day;
        arr[j++] = D.GetY();
        arr[j++] = D.GetM();
        arr[j++] = D.GetD();
    }

    for(int i = 0;i<3*m2;i+=3) //err跳跃错误
    {
        cout << setfill('0') << setw(4) << arr[i];
        cout << "-";
        cout << setfill('0') << setw(2) << arr[i+1];
        cout << "-";
        cout << setfill('0') << setw(2) << arr[i+2] << endl;
    }
}
// 64 位输出请用 printf("%lld")