#include<iostream>
#include<string>

using namespace std;

class DrawCircle
{
    public:
        // int radius,x,y;  /*定義參數(shù)為int radius, int x, int y*/

        virtual void drawCircle(int radius, int x, int y) = 0;  //(1)
        virtual ~DrawCircle()
        {

        }
};

class RedCircle : public DrawCircle
{
    /*繪制紅色圓形*/
    public:
        void drawCircle(int radius, int x, int y)
        {
            cout << "DrawingCircle: red, radius: " <<radius <<" x: "<< x <<" y: "<< y <<endl;
        }
};

class GreenCircle : public DrawCircle
{
    /*繪制綠色圓形*/
    public:
        void drawCircle(int radius, int x, int y)
        {
            cout << "DrawingCircle: green, radius: " <<radius <<" x: "<< x <<" y: "<< y <<endl;
        }
};

class Shape
{
    protected:
        DrawCircle* drawCircle;  //(2)
    public:
        Shape(DrawCircle* drawCircle)
        {
            this->drawCircle = drawCircle;
        }

        virtual ~Shape()
        {

        }

    public:
        virtual void draw() = 0;
};

class Circle : public Shape
{
    private:
        int x, y, radius;
    
    public:
        // Circle(int x,int y, int radius, DrawCircle* drawCircle):Shape(drawCircle)
        Circle(int x,int y, int radius, DrawCircle* drawCircle):Shape(drawCircle)  //(3)
        {
            this->x = x;
            this->y = y;
            this->radius = radius;
        }

    public:
        void draw()
        {
            drawCircle->drawCircle(radius, x, y);  //(4)
        }
};

int main()
{
    Shape *redCircle = new Circle(100,100,20,(new RedCircle()));  //(5)
    Shape *greenCircle = new Circle(100,100,20,(new GreenCircle()));  //(6)
    redCircle->draw();
    greenCircle->draw();
    return 0;
}

答案：
(1) virtual void drawCircle(int radius, int x, int y) = 0;

(2) DrawCircle* drawCircle;

(3) :Shape(drawCircle)

(4) drawCircle(radius, x, y);

(5) new RedCircle()

(6) new GreenCircle()