前言：

参考：B站UP主鱼C_小甲鱼<C++快速入门>
代码调试平台：VS2017，调试成功。

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问题描述：

问题描述：记录猫狗数量（静态变量）。

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代码实现：

//静态变量static
#include<iostream>
#include <string>

using namespace std;

class Pet
{
public:
	Pet(string theName);
	~Pet();
	
	static int getcount();
protected:
	string name;
private:
	static int count;
};
class Dog:public Pet
{
public:
	Dog(string theName);
};
class Cat :public Pet
{
public:
	Cat(string theName);
};

int Pet::count = 0;  //为count分配了内存空间，并赋值

Pet::Pet(string theName)
{
	name = theName;
	count++;

	cout << "一只动物出生了,名字是" <<name<<"\n"<< endl;
}
Pet::~Pet()
{
	count--;
	cout << name << "挂掉了。" << "\n" << endl;
}

int Pet::getcount()
{
	return count;
}

Dog::Dog(string theName) :Pet(theName)
{

}
Cat::Cat(string theName) : Pet(theName)
{

}

int main()
{
	Dog dog("Tom");
	Cat cat("Jerry");

	cout << "已经诞生了" << Pet::getcount() << "只动物。\n"<<endl;
	{
		Dog dog2("TP");
		Cat cat1("je");

		cout << "\n现在已经诞生了" << Pet::getcount() << "只宠物.\n" << endl;
	}

	cout << "现在还剩" << Pet::getcount() << "只宠物！\n";

	return 0;
}