#include <iostream>

using namespace std;

#define cendl cout << endl;

class AA{//这是一个纯虚函数

public :

    virtual void fun() = ;

};

class A{

    int data_a;

public:

    A(){

        data_a = ;

        cout << "A " ;

    }

    A(int a){

        data_a = a;

        cout << "A(a) " ;

    }

    void show(){

        cout << data_a<<' ' ;

    }

    virtual void fun(){

        cout << "this is A ";

    }

    ~A(){

        cout << "~A " ;

    }

};

class B : public A{

    int data_b;

public:

    B(){

        data_b = ;

        cout << "B " ;

    }

    B(int a, int b) :A(a){

        data_b = b;

        cout << "B(a) " ;

    }

    void show(){

        A::show();

        cout << data_b << ' ';

    }

    virtual void fun(){

        cout << "this is B ";

    }

    ~B(){

        cout << "~B " ;

    }

};

class C :public A{
int data_c;
public:
C(){ data_c = 3; cout << "C " ; }
C(int a, int b) :A(a){
data_c = b;
cout << "C(a) " ;
}
void show(){
A::show();
cout << data_c << ' ';
}
virtual void fun(){
cout << "this is C ";
}
~C(){
cout << "~C " ;
}
};

int main()

{

A *a1 = new A(2);
cendl;
A *a2 = new B(2,3);
cendl;
A *a3 = new C(2, 3);
cendl;
a1->fun();
cendl;
a2->fun();
cendl;
a3->fun();
cendl;
delete a1;
cendl;
delete a2;
cendl;
delete a3;
system("pause");
return 0;

}