虚函数与纯虚函数

为了模拟毒株变异、生活在我们体内以及被我们免疫系统消灭的过程，乎优塔写了以下程序，请补充完整程序，并运行出毒株灭亡的结果。

#include <iostream>

using namespace std;

class Virus {

public:

Virus() {

cout << "I am the ancestor of the new virus!" << endl;

}

~Virus() {

cout << "I must disappear!" << endl;

}

_____________________; //定义纯虚函数

};

class vOne : public Virus

{

public:

vOne() {

cout << "vOne is born." << endl;

}

~vOne() {

cout << "vOne is dead." << endl;

}

void eat() {

cout << "vOne is living in your body." << endl;

}

};

class vTwo : public Virus

{

public:

vTwo() {

cout << "vTwo is born." << endl;

}

~vTwo() {

cout << "vTwo is dead." << endl;

}

void eat() {

cout << "vTwo is living in your body." << endl;

}

};

int main() {

_____________________; //定义父类指针v

_____________________; //定义vOne对象v1

_____________________; //定义vTwo对象v2

v = &v1;

_____________________; //通过父类指针调用eat()方法

v = &v2;

_____________________; //通过父类指针调用eat()方法

cout << "Our immune system is kill v1 and v2..." << endl;

return 0;

}

这道题让我明白了，如何实现虚函数与纯虚函数。