Programación orientada a objetos en C ++ 026: Complete los espacios en blanco en la programación: cuente el número de animales ---- (Beijing University Mooc)

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Titulo original

#include <iostream>
using namespace std;
// 在此处补充你的代码
void print() {
    
    
	cout << Animal::number << " animals in the zoo, " << Dog::number << " of them are dogs, " << Cat::number << " of them are cats" << endl;
}

int main() {
    
    
	print();
	Dog d1, d2;
	Cat c1;
	print();
	Dog* d3 = new Dog();
	Animal* c2 = new Cat;
	Cat* c3 = new Cat;
	print();
	delete c3;
	delete c2;
	delete d3;
	print();
}

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Código

class Animal{
    
    
public:
    static int number;
    virtual ~Animal(){
    
    number--;}
};

class Dog:public Animal{
    
    
public:
    static int number;
    Dog()
    {
    
    
        Animal::number++;
        Dog::number++;
    }
    ~Dog(){
    
    number--;}

};

class Cat:public Animal{
    
    
public:
    static int number;
    Cat()
    {
    
    
        Animal::number++;
        Cat::number++;
    }
    ~Cat(){
    
    number--;}

};

int Animal::number = 0,Dog::number = 0,Cat::number = 0;