日期類定義

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

class Date {
 public:
  void setDate(int year, int month, int day);
  int year() const;
  int month() const;
  int day() const;

  std::string toString() const {
    const int length_of_date_string = 10;

    char date_string[length_of_date_string + 1];
    snprintf(date_string,
            length_of_date_string + 1,
            "%04d-%02d-%02d",
            year_, month_, day_);

    return std::string(date_string);
  }

  void increase();
  void decrease();

 private:
  int year_;
  int month_;
  int day_;

  int daysOfMonth(int year, int month) const;
};

void Date::setDate(int year, int month, int day){
    year_=year;
    month_=month;
    day_=day;
}
int Date::year() const{
    return year_;
}
int Date::month() const{
    return month_;
}
int Date::day() const{
    return day_;
}
int Date::daysOfMonth(int year, int month) const{
    if(month%2==0&&month>=8)return 31;
    else if (month%2!=0&&month<=7)return 31;
    else if(month!=2)return 30;
    else if(year%400==0||(year%4==0&&year%100!=0))return 29;
    else return 28;
}
void Date::increase(){
    day_++;
    if(day_>daysOfMonth(year_,month_)){
        day_ = 1;
        month_++;
        if(month_>12){
            year_++;
            month_=1;
        }
    }
}
void Date::decrease(){
    day_--;
    if(day_==0){
        month_--;
        if(month_==0){
            year_--;
            month_=12;
            day_=31;
        }
        day_=daysOfMonth(year_,month_);
    }
}


void TestDate(Date& date, int after, int before) {
  cout << "Year: " << date.year() << endl
       << "Month: " << date.month() << endl
       << "Day: " << date.day() << endl;
  cout << "Formatted: " << date.toString() << endl;

  date.increase();
  cout << "1 day later: " << date.toString() << endl;
  for (int i = 0; i < after; ++i) {
    date.increase();
  }
  cout << "Another " << after << " day(s) later: " << date.toString() << endl;
  for (int i = 0; i < before; ++i) {
    date.decrease();
  }
  cout << "Another " << before << " day(s) earlier: " << date.toString() << endl;
}

int main() {
  int year, month, day;
  int after, before;
  cin >> year >> month >> day;
  cin >> after >> before;

  Date date;
  date.setDate(year, month, day);
  TestDate(date, after, before);

  return 0;
}

//還是良心附有測試main函數，先叉會腰冷靜一下