class Shape {
public:
    virtual void draw() {
        cout << "绘制图形" << endl;
    }
    virtual ~Shape() {}
};
class Circle : public Shape {
public:
    void draw() override {
        cout << "绘制圆形" << endl;
    }
};
class Rectangle : public Shape {
public:
    void draw() override {
        cout << "绘制矩形" << endl;
    }
};
int main() {
    Shape* s1 = new Circle();
    Shape* s2 = new Rectangle();
    s1->draw();
    s2->draw();
    delete s1;
    delete s2;
    return 0;
}