第3题

#include <iostream>
using namespace std;
class Date
 {public:
   Date(int=1,int=1,int=2005);
   void display();
  private:
   int month;
   int day;
   int year;
 };
Date::Date(int m,int d,int y):month(m),day(d),year(y)
 { }
void Date::display()
 {cout<<month<<"/"<<day<<"/"<<year<<endl;}
int main()
{
 Date d1(10,13,2005);
 Date d2(12,30);
 Date d3(10);
 Date d4;
 d1.display();
 d2.display();
 d3.display();
 d4.display();
 return 0;
}