C++第三次作业

#include <iostream>
using namespace std;
class Date;
class Time
{
public:
Time(int,int,int);
void add_a_second(Date &);
void display(Date &);
private:
int hour;
int minute;
int sec;
};

class Date
{
public:
Date(int,int,int);
friend class Time;
private:
int month;
int day;
int year;
};

int main( )
{
Time t1(23,59,32);
Date d1(12,31,2013);
for(int i=0; i<=80; i++)
{
t1.add_a_second(d1);
t1.display(d1);
}
return 0;
}

Time::Time(int h,int m,int s)
{
hour=h;
minute=m;
sec=s;
}
Date::Date(int m,int d,int y)
{
month=m;
day=d;
year=y;
}
void Time::add_a_second(Date &d)
{
if(++sec>=60) ++minute,sec-=60;
if(minute>=60) ++hour,minute-=60;
if(hour>=24) ++d.day,hour-=24;
if(d.day>30) ++d.month,d.day-=30;
if(d.month>12) ++d.year,d.month-=12;
}
void Time::display(Date &d)
{
cout<<d.month<<"/"<<d.day<<"/"<<d.year<<" ";
cout<<hour<<":"<<minute<<":"<<sec<<endl;
}

#include<iostream>
#include<Cmath>
using namespace std;
class CPoint
{
private:
double x;
double y;
public:
CPoint(double xx=0,double yy=0):x(xx),y(yy) {}
double distance1(CPoint &);
friend double distance2(CPoint &, CPoint &) ;
double getX()
{
return x;
}
double getY()
{
return y;
}
};

double distance3(CPoint &,CPoint &) ;

double CPoint::distance1(CPoint &p)
{
double dx=(x-p.x), dy=y-p.y;
return sqrt(dx*dx+dy*dy);
}

double distance2(CPoint &p1,CPoint &p2)
{
double dx=(p1.x-p2.x), dy=p1.y-p2.y;
return sqrt(dx*dx+dy*dy);
}

double distance3(CPoint &p1,CPoint &p2)
{
double dx=(p1.getX()-p2.getX()), dy=p1.getY()-p2.getY();
return sqrt(dx*dx+dy*dy);
}

int main()
{
CPoint p1(10,13), p2(-5,6);
cout<<"1. "<<p1.distance1(p2)<<endl;
cout<<"2. "<<distance2(p1,p2)<<endl;
cout<<"3. "<<distance3(p1,p2)<<endl;
return 0;
}