#include <iostream>
 
class Animal
{
public:
    virtual ~Animal() {};
 
    virtual void doSmth() = 0;
};
 
class Cat : public Animal
{
public:
    void doSmth() override
    {
        std::cout << "Miau" << std::endl;
    }
};
 
class Dog : public Animal
{
public:
    void doSmth() override
    {
        std::cout << "Wuff" << std::endl;
    }
};
 
int main()
{
    Dog dog;
    Cat cat;
 
    Animal *animal = &dog;
    animal->doSmth();
 
    animal = &cat;
    animal->doSmth();
 
    return 0;
}
 

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