#include <iostream>using namespace std;#define cendl cout << endl;class AA{//这是一个纯虚函数public :    virtual void fun() = 0;};class A{    int data_a;public:    A(){        data_a = 1;        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 = 2;        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;

}