C++第三次作业（补）

项目三：友元类

#include <iostream>  
using namespace std;  
class Date; //对Date类的提前引用声明  
class Time  
{  
public:  
    Time(int,int,int);  
    void add_a_second(Date &);  //增加1秒，1秒后可能会到了下一天，乃到下一月、下一年  
    void display(Date &);  //显示时间，格式：月/日/年 时:分:秒  
private:  
    int hour;  
    int minute;  
    int sec;  
};  
class Date  
{  
public:  
    Date(int,int,int);  
    friend class Time; //Time为Date的友元类  
private:  
    int month;  
    int day;  
    int year;  
};  
Date::Date(int m,int d,int y):year(y),day(d),month(m){}  
Time::Time(int h,int m,int s):hour(h),minute(m),sec(s){}  
void Time::add_a_second(Date &d)  
{  
    sec=sec+1;  
    if(sec==60)  
    {  
        minute=minute+1;  
        sec=0;  
        if(minute==60)  
        {  
            hour=hour+1;  
            minute=0;  
            if(hour>=24)  
            {  
                d.day=d.day+1;  
                hour=0;  
                if(d.day==29)  
                {  
                    while(d.month==2)  
                    {  
                        d.month=d.month+1;  
                    }  
                    d.day=1;  
                }  
                if(d.day==31)  
                {  
                    while(d.month==4||d.month==6||d.month==9||d.month==11)  
                    {  
                        d.month=d.month+1;  
                    }  
                    d.day=1;  
                }  
                if(d.day==32)  
                {  
                    while(d.month==1||d.month==3||d.month==5||d.month==7||d.month==8||d.month==10||d.month==12)  
                    {  
                        d.month=d.month+1;  
                    }  
                    d.day=1;  
                    if(d.month==13)  
                    {  
                        d.year=d.year+1;  
                        d.month=1;  
                    }  
                }  
  
            }  
        }  
    }  
  
}  
void Time::display(Date &d)  
{  
    cout<<d.year<<"/"<<d.month<<"/"<<d.day<<" "<<hour<<":"<<minute<<":"<<sec<<endl;  
}  
int main( )  
{  
    Time t1(23,59,32);  
    Date d1(12,31,2013);   //测试时，再试试Date d1(2,28,2013)会如何  
    for(int i=0; i<=100; i++)  
    {  
        t1.add_a_second(d1);  
        t1.display(d1);  
    }  
    return 0;  
}  
//下面定义两个类中的成员函数，要求不得再增加成员函数  
//注意体会在Time的成员函数中可以调用Date类的私有数据成员  

项目一：静态成员应用

#include <iostream>    
using namespace std;    
class Time{    
public:    
    Time(int=0,int=0,int=0);    
    void show_time( );   
    void add_seconds(int n);   
    void add_minutes(int n);   
    void add_hours(int n);   
    static void change24();    
    static void changefrom0();    
 private:    
    static bool is_24;   
    static bool from0;   
    int hour;    
    int minute;    
    int sec;    
};    
bool Time::is_24=true;  
bool Time::from0=false;  
Time::Time(int h,int m,int s)  
{  
    hour=h;minute=m;sec=s;  
}  
void Time::show_time()  
{  
    if(is_24)  
    {  
        if(from0)  
            cout<<(hour<10?"0":"")<<hour<<":"<<(minute<10?"0":"")<<minute<<":"<<(sec<10?"0":"")<<sec<<endl;  
        else  
            cout<<hour<<":"<<minute<<":"<<sec<<endl;  
    }  
    else  
    {  
        if(from0)  
        {  
            if(hour<12)  
            {   cout<<(hour<10?"0":"")<<hour<<":"<<(minute<10?"0":"")<<minute<<":"<<(sec<10?"0":"")<<sec<<"   AM"<<endl;}  
            else   
            {   cout<<((hour-12)<10?"0":"")<<hour-12<<":"<<(minute<10?"0":"")<<minute<<":"<<(sec<10?"0":"")<<sec<<"   PM"<<endl;}  
        }  
        else  
        {  
            if(hour<12)  
            {   cout<<hour<<":"<<minute<<":"<<sec<<"   AM"<<endl;}  
            else  
            {   cout<<hour-12<<":"<<minute<<":"<<sec<<"   PM"<<endl;}  
    }  
    }  
}  
  
        void Time::add_seconds(int n)  
        {  
            n+=sec;  
            minute+=n/60;  
            sec=n%60;  
        }  
        void Time::add_minutes(int n)  
        {  
            n+=minute;  
            hour+=n/60;  
            minute=n%60;  
        }  
        void Time::add_hours(int n)  
        {  
            hour=(hour+n)%24;  
        }  
     void Time::change24()  
        {  
            is_24=false;  
        }  
     void Time::changefrom0()  
        {  
            from0=true;  
        }  
        int main()  
        {  
            Time p1(23,14,25),p2(8,45,6);  
            cout<<"24小时制，不前导："<<endl;  
            p1.show_time();  
            p2.show_time();  
            p1.add_hours(10);  
            p2.add_hours(10);  
            p1.changefrom0();  
            p2.changefrom0();  
            cout<<"10小时后，切换是否前导："<<endl;  
            p1.show_time();  
            p2.show_time();  
            p1.change24();  
            p2.change24();  
            cout<<"换一种制式："<<endl;  
            p1.show_time();  
            p2.show_time();  
            return 0;  
        }