Question

急~用C++的高手帮忙一下

设计一个基类base为抽象类，其中包含gettitle()和printtitle()两个成员函数，另有一个纯虚函数isgood()。由该类派生Book和Journal两个类，分别实现纯函数isgood()对于前者版本，如果每月图书销售量超过500，则返回True；对于后者版本，如果每月杂志销售量超过2500，则返回True。

Answer 1

你没有说清楚gettitle和printtitle的作用呢，下面按你要求写的，不知道是不是你所说的那样
class base
{
public:
void gettitle(){}
void printtitle(){}
virtual bool isgood() = 0;
};

class Book : public base
{
public:
bool isgood()
{
if (sold > 500)
{
return true
}
return false;
}
private:
int sold;
};

class Journal : public base
{
public:
bool isgood()
{
if (sold > 2500)
{
return true
}
return false;
}
private:
int sold;
};

追问

感谢你的回答~gettitle和printtitle应该是书的资料（可能是书的书名）的录入和输出吧~我大概猜的

Answer 2

#include <iostream>
using namespace std;

class base
{
private:
int sales;
public:
base()
{
cout<<"base"<<endl;
}
base(int t)
{
sales = t;
cout<<"base sales"<<endl;
}
int gettitle()
{
return sales;
}
void printtitle()
{
cout<<sales<<endl;;
}
virtual bool isgood() = 0;
};

class Book:public base
{
public:
Book(int t):base(t)
{
cout<<"Book sales"<<endl;
}
bool isgood()
{
if (gettitle() >= 500)
{
cout<<"Book sales return true"<<endl;
return true;
}
return false;
}

};
class Journal:public base
{
public:
Journal(int t):base(t)
{
cout<<"Journal sales"<<endl;
}
bool isgood()
{
if (gettitle() >= 2500)
{
cout<<"Journal sales return true"<<endl;
return true;
}
return false;
}
};

void main()
{
base *a;
Book b(600);
a = &b;
a->isgood();
Journal c(3600);
a = &c;
a->isgood();
system("pause");
}

Answer 3

注意纯虚函数定义成virtual bool isgood() = 0;
这样就OK了，其他的都很基础！
另外，你让写的是伪码，楼上写的不错。

Answer 4

#include <iostream>
#include <string>
using namespace std;

class base{
string title;
int sales;
public:
base(string str,int s=0){title=str;sales=s;}
string gettitle(){return title;}
void printtitle(){cout<<title;}
int getsales(){return sales;}
virtual bool isgood(){return true;}
};

class Book:public base{
public:
Book(string str,int s=0):base(str,s){}
bool isgood(){return getsales()>500;}
};

class Journal:public base{
public:
Journal(string str,int s=0):base(str,s){}
bool isgood(){return getsales()>2500;}
};

void main()
{
base *p[2];
p[0]=new Book("abc",600);
p[1]=new Journal("xyz",2000);
if(p[0]->isgood())
cout<<"abc is good."<<endl;
else
cout<<"abc isn't good."<<endl;
if(p[1]->isgood())
cout<<"xyz is good."<<endl;
else
cout<<"xyz isn't good."<<endl;
delete p[0];
delete p[1];
}