c 一道面试题【继承，多态】

     写出下面函数的正确输出结果：

#if (__GNUC__ > 2)
#include <iostream>
using std::cerr;
using std::cout;
using std::endl;
using std::flush;
#else
#include <iostream.h>
#endif

using namespace std;

class Base{public:
    virtual void f(float x){ cout << "Base::f(float) " << x << endl; }
    void g(float x){ cout << "Base::g(float) " << x << endl; }
    void h(float x)={ cout << "Base::h(float) " << x << endl; }
};



class Derived : public Base{
public:
   virtual void f(float x){ cout << "Derived::f(float) " << x << endl; }
   void g(int x){ cout << "Derived::g(int) " << x << endl; }
   void h(float x){ cout << "Derived::h(float) " << x << endl; }
};


int main(void){
    Derived d;//派生类对象
    Base *pb = &d;
    Derived *pd = &d;
    pb->f(3.14f);//由virtual 虚函数重写，基类指针指向派生类对象，从而实现多态
    pd->f(3.14f);

    pb->g(3.14f);//基类和派生类都定义了“相同名称之函数”，那么通过对象指针调用成员函数时，到底调用了那个函数，必须视该指针的原始类型而定，而不是视指针实际所指的对象的类型而定
    pd->g(3.14f); //pd 原型为派生类，所以调用派生类的成员函数

    pb->h(3.14f);
    pd->h(3.14f);
    return 1;
}

该题考查了c++的基础知识，基类与派生类之间的关系，基类与派生类实现的多态（virtual的应用）

g++编译后执行结果为

[root@localhost linuxstudy]# ./teituo 

Derived::f(float) 3.14

Derived::f(float) 3.14

Base::g(float) 3.14

Derived::g(int) 3

Base::h(float) 3.14

Derived::h(float) 3.14

[root@localhost linuxstudy]#