第11题

#include <iostream>using namespace std;class Time;class Date {public:   Date(int,int,int);   friend Time;private:   int month;   int day;   int year; };Date::Date(int m,int d,int y):month(m),day(d),year(y){ }class Time {public:   Time(int,int,int);   void display(const Date &);  private:   int hour;   int minute;   int sec; };Time::Time(int h,int m,int s):hour(h),minute(m),sec(s){ }void Time::display(const Date &d) {  cout<<d.month<<"/"<<d.day<<"/"<<d.year<<endl;  cout<<hour<<":"<<minute<<":"<<sec<<endl; }int main(){ Time t1(10,13,56); Date d1(12,25,2004); t1.display(d1); return 0;}