声明一个哺乳动物类Mammal，再由此派生出狗类Dog和猫类Cat。 程序要求： （1）Mammal类中定义名为color和weight的数据成员，分别用来存储动物的颜色和体重；并在Mammal类中定义一个虚函数print，用于输出color和weight值。 （2）每个类中都定义一个名为count的静态数据成员，用来存储各类对象的总数； （3）每个类都有构造函数和析构函数，在构造函数中对color和weight进行初始化，以及执行count++语句，在析构函数中执行count--语句。在Dog和Cat类中输出各自的信息，输出信息要有所区别； （4）主函数中以一般方法定义各类若干个对象，用new创建几个对象指针，用delete删除对象指针。在不同的位置输出各类count的值。最后输出"Main function ends."。

好的，以下是代码实现：

#include <iostream>
using namespace std;

// 哺乳动物类
class Mammal {
public:
    Mammal(string c, double w) : color(c), weight(w) { count++; }
    virtual ~Mammal() { count--; }
    virtual void print() { cout << "Color: " << color << ", Weight: " << weight << endl; }
    static int count;
protected:
    string color;
    double weight;
};

int Mammal::count = 0;

// 狗类
class Dog : public Mammal {
public:
    Dog(string c, double w, string b) : Mammal(c, w), breed(b) { count++; }
    ~Dog() { count--; }
    void print() { cout << "This is a dog. Breed: " << breed << ", "; Mammal::print(); }
    static int count;
private:
    string breed;
};

int Dog::count = 0;

// 猫类
class Cat : public Mammal {
public:
    Cat(string c, double w, bool f) : Mammal(c, w), isFat(f) { count++; }
    ~Cat() { count--; }
    void print() { cout << "This is a cat. Is fat: " << (isFat ? "yes" : "no") << ", "; Mammal::print(); }
    static int count;
private:
    bool isFat;
};

int Cat::count = 0;

int main() {
    Mammal m1("brown", 30), m2("black", 50);
    Dog* d1 = new Dog("white", 20, "Golden Retriever");
    Dog* d2 = new Dog("black", 25, "Labrador");
    Cat* c1 = new Cat("gray", 5, false);
    Cat* c2 = new Cat("white", 3, true);

    cout << "Mammal count: " << Mammal::count << endl;
    cout << "Dog count: " << Dog::count << endl;
    cout << "Cat count: " << Cat::count << endl;

    m1.print();
    m2.print();
    d1->print();
    d2->print();
    c1->print();
    c2->print();

    delete d1;
    delete d2;
    delete c1;
    delete c2;

    cout << "Mammal count: " << Mammal::count << endl;
    cout << "Dog count: " << Dog::count << endl;
    cout << "Cat count: " << Cat::count << endl;

    cout << "Main function ends." << endl;
    return 0;
}

输出结果如下：

Mammal count: 6
Dog count: 2
Cat count: 2
Color: brown, Weight: 30
Color: black, Weight: 50
This is a dog. Breed: Golden Retriever, Color: white, Weight: 20
This is a dog. Breed: Labrador, Color: black, Weight: 25
This is a cat. Is fat: no, Color: gray, Weight: 5
This is a cat. Is fat: yes, Color: white, Weight: 3
Mammal count: 2
Dog count: 0
Cat count: 0
Main function ends.

可以看到，程序按照要求正确地输出了各个类的信息和对象数量，并正确地进行了内存管理。