#include<iostream>
#include<stdlib.h>
#include<unistd.h>
#include<stdio.h>
using namespace std;
class B0
{
public:
    virtual void display()                                  //虚函数
    {
        cout<<"B0 display"<<endl;   
    }
};
class B1:public B0
{
public:
    void display()
    {
        cout<<"B1 display"<<endl;   
    }
};
class B2:public B1
{
public:
    void display()
    {
        cout<<"B2 display"<<endl;   
    }
};
int main()
{     
    B0 b,*p0;
    p0=&b;
    p0->display();
    B1 b1;
    p0=&b1;
    p0->display();
    B2 b2;
    p0=&b2;
    p0->display();
    /*B2* b2;
    b2->display();
    b2->B1::display();
    b2->B0::display();*/
    return 0; 
}