项目一（静态成员用于时间类）

#include<iostream>
#include"Time.h"
using namespace std;
int main( )
{
Time t1(23,54,53),t2(11,58,59);
cout<<"24时制, 不前导："<<endl;
cout<<"t1是：";
t1.show_time();
cout<<"t2是：";
t2.show_time();
t1.add_hours(10);
t2.add_hours(10);
Time::changefrom0();
cout<<"10小时后, 切换是否前导："<<endl;
cout<<"t1是：";
t1.show_time();
cout<<"t2是：";
t2.show_time();
t2.change24();
cout<<"换一种制式："<<endl;
cout<<"t1是：";
t1.show_time();
cout<<"t2是：";
t2.show_time();
system("pause");
return 0;
}

#include<iostream>
#include "Time.h"
using namespace std;
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( )
{
int h=(is_24)?hour:hour%12;
if (h<10&&from0) cout<<"0";
cout<<h<<":";
if(minute<10&&from0) cout<<"0";
cout<<minute<<":";
if(sec<10&&from0) cout<<"0";
cout<<sec;
if(!is_24)
{
cout<<((hour>12)?"  pm":"  am");
}
cout<<endl;
}

void Time::add_seconds(int n)
{
sec+=n;
if (sec>59)
{
add_minutes(sec/60);
sec%=60;
}
}

void Time::add_minutes(int n)
{
minute+=n;
if (minute>59)
{
add_hours(minute/60);
minute%=60;
}
}

void Time::add_hours(int n)
{
hour+=n;
if (hour>23)
hour%=24;
}

void Time::change24()
{
is_24=!is_24;
}
void Time::changefrom0()
{
from0=!from0;
}

#pragma once
class Time
{
public:
Time(int=0,int=0,int=0);
void show_time( ); //根据is_24和from0，输出适合形式的时间:23:5/8:23:5 pm/08:23:05 pm
void add_seconds(int); //增加n秒钟
void add_minutes(int); //增加n分钟
void add_hours(int); //增加n小时
static void change24();  //改变静态成员is_24，在和时制之间转换
static void changefrom0();   //改变静态成员from0，转换是否前导
private:
static bool is_24; //为true时，小时制，如:23:5；为flase，小时制，显示为:23:5 pm
static bool from0; //为true时，前导，:23:5显示为:23:05
int hour;
int minute;
int sec;
};