#include <iostream>
#include <vector>
 
struct Animal {
    virtual void talk() = 0;
};
 
struct Dog : Animal {
    void talk() override {
        std::cout << "guau guau" << std::endl;
    }
};
 
struct Cat : Animal {
    void talk() override {
        std::cout << "miau miau" << std::endl;
    }
};
 
int main() {
    auto x = Dog{};
    auto y = Cat{};
 
    std::vector<Animal*> pets{&x, &y};
 
    for(auto& pet : pets) {
        pet->talk();
    }
 
    return 0;
}

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