Question

C++中继承类的问题

# include "iostream.h"
# include "string.h"

class clock
{
private:
int hour;
int minute;
int second;
public:
clock(int hour = 0,int minute = 0,int second = 0);
int return_hour();
void output();
};

class Newclock:public clock
{
private:
char a[10];
public:
Newclock(int hour = 0,int minute = 0,int second = 0,char a = NULL);
void judge_AM_PM();
void output();
};

clock::clock(int hour, int minute, int second)
{
this -> hour = hour;
this -> minute = minute;
this -> second = second;
}

int clock::return_hour()
{
return hour;
}

void clock::output()
{
cout<<"The time is :"<<endl;
cout<<hour<<":"<<minute<<":"<<second<<endl;
}

Newclock::Newclock(int hour,int minute,int second,char a):clock(hour,minute,second);

void Newclock::judge_AM_PM()
{
if (clock::return_hour > 12)
{
strcpy(a,"AM");
}

else
{
strcpy(a,"PM");
}
}

void Newclock::output()
{
clock::output();
cout<<a<<endl;
}

void main()
{
Newclock time(8,12,13);

time.judge_AM_PM();
time.output();

}

这个程序的功能是：将输入的一个时间（比如：13：12：14）改成（1：12：14 PM），即加上 AM 还是PM，但我运行时，遇到了很多麻烦。怎么改都不行。请高手帮忙改一下。
错误如下：
error C2062: type 'void' unexpected
error C2630: ';' found in what should be a comma-separated list
error C2296: '>' : illegal, left operand has type 'int (__thiscall clock::*)(void)'
error C2664: 'strcpy' : cannot convert parameter 1 from 'char' to 'char *'
type to pointer type requires reinterpret_cast, C-style cast or function-style cast
error C2664: 'strcpy' : cannot convert parameter 1 from 'char' to 'char *'

Answer 1

编译时两个地方有错，功能部分未实现
# include <iostream>
# include <string>

using namespace std;

class clock
{
private:
int hour;
int minute;
int second;
public:
clock(int hour = 0,int minute = 0,int second = 0);
int return_hour();
void output();
};

class Newclock:public clock
{
private:
char a[10];
public:
Newclock(int hour = 0,int minute = 0,int second = 0,char a = NULL);
void judge_AM_PM();
void output();
};

clock::clock(int hour, int minute, int second)
{
this -> hour = hour;
this -> minute = minute;
this -> second = second;
}

int clock::return_hour()
{
return hour;
}

void clock::output()
{
cout<<"The time is :"<<endl;
//
// 实现将输入的一个时间（比如：13：12：14）改成（1：12：14 PM），也就是hour
//如果大于12，就减12
//
if (hour > 12)
hour -= 12;
cout<<hour<<":"<<minute<<":"<<second<<endl;
}

Newclock::Newclock(int hour,int minute,int second,char a):clock(hour,minute,second)
//上面已经声明过了！这里必须定义
{}

void Newclock::judge_AM_PM()
{
if (clock::return_hour() > 12) // 加上函数参数列表，也就是（）
{
strcpy(a,"AM");
}

else
{
strcpy(a,"PM");
}
}

void Newclock::output()
{
clock::output();
cout<<a<<endl;
}

void main()
{
Newclock time(16,12,13);

time.judge_AM_PM();
time.output();

}

Answer 2

#include <iostream>
#include "string.h"

using namespace std;
class clock
{
private:
int hour;
int minute;
int second;
public:
clock(int hour = 0,int minute = 0,int second = 0);
int return_hour();
void output();
};

class Newclock:public clock
{
private:
char a[10];
public:
Newclock(int hour = 0,int minute = 0,int second = 0,char a = NULL);
void judge_AM_PM();
void output();
};

clock::clock(int hour, int minute, int second)
{
this -> hour = hour;
this -> minute = minute;
this -> second = second;
}

int clock::return_hour()
{
return hour;
}

void clock::output()
{
cout<<"The time is :"<<endl;
cout<<hour<<":"<<minute<<":"<<second<<endl;
}

Newclock::Newclock(int hour,int minute,int second,char a):clock(hour,minute,second){};//
//必须要有函数体

void Newclock::judge_AM_PM()
{
if (clock::return_hour() > 12)//函数调用要有()
{
strcpy(a,"AM");
}

else
{
strcpy(a,"PM");
}
}

void Newclock::output()
{
clock::output();
cout<<a<<endl;
}

int main()
{
Newclock time(8,12,13);

time.judge_AM_PM();
time.output();

}