2018年上半年程序员考试第六题目，解析

阅读下列说明和C++代码，填写程序中的空（1）～（6），将解答写入答题纸的对应栏内。

【说明】

以下C++代码实现一个简单绘图工具，绘制不同形状以及不同颜色的图形。部分类及其关系如图6－1所示。

【C++代码】

#include

#include

using namespace std;

class DrawCircle { //绘制圆形，抽象类

public:

（1） ；//定义参数为 int radius, int x, int y

virtual～DrawCircle() { }

};

 

class RedCircle：public DrawCircle { //绘制红色圆形

public:

void drawCircle(int radius, int x, int y) {

cout << "Drawing Circle[red,radius: " <

cout << ",x: " <

}

};

 

class GreenCircle：public DrawCircle { //绘制绿色圆形

public:

void drawCircle(int radius, int x, int y) {

cout <<"Drawing Circle[green,radius: " << radius;

cout <<",x: " <

}

};

 

class Shape { //形状，抽象类

protected:

（2） ;

public:

Shape(DrawCircle *drawCircle) {

this -> drawCircle = drawCircle;

}

virtual～shape() { }

public:

virtual void draw() = 0;

};

 

class Circle：public Shape { //圆形

private:

int x,y,radius;

public:

Circle(int x,int y,int radius,DrawCircle *drawCircle) （3） {

this->x = x;

this->y = y;

this->radius = radius;

}

public:

void draw() {

drawCircle -> （4） ;

}

};

 

int main()

{

Shape *redCircle＝new Circle(100,100,10, （5） );//绘制红色圆形

Shape *greenCircle＝new Circle(100,100,10, （6） );//绘制绿色圆形

redCircle ->draw();

greenCircle ->draw();

return 0;

}

 

上机测试了一下：得到的结论答案：某些网站给的错误的答案

（1）virtual void drawCircle(int radius, int x, int y)=0; //因为下面的class Circle的draw调用了，所以需要是纯虚函数。

（2）DrawCircle *drawCircle

（3）:Shape(drawCircle)

（4）drawCircle(radius, x, y)

（5）new RedCircle()

（6）new GreenCircle()

 

一下可以测试一下跑在vs2005下代码：

#include 

#include 

using namespace std;

class DrawCircle {      //绘制圆形，抽象类

public:

	virtual void drawCircle(int radius, int x, int y)=0;//定义参数为 int radius, int x, int y,-----(1)

	virtual~ DrawCircle() { }

};



class RedCircle : public DrawCircle {     //绘制红色圆形

public:

	void drawCircle(int radius, int x, int y) {

		cout << "Drawing Circle[red,radius: " << radius;

		cout << ",x: " << x << ",y: " << y << "]" << endl;

	}

};



class GreenCircle : public DrawCircle {    //绘制绿色圆形

public:

	void drawCircle(int radius, int x, int y) {

		cout << "Drawing Circle[green,radius: " << radius;

		cout << ",x: " << x << ",y: " << y << "]" << endl;

	}

};



class Shape {    //形状，抽象类

protected:

	DrawCircle* drawCircle;///-------------------(2)

public:

	Shape(DrawCircle *drawCircle) {

		this->drawCircle = drawCircle;

	}

	virtual~ Shape() { }

public:

	virtual void draw()=0;

};



class Circle : public Shape {    //圆形

private:

	int x, y, radius;

public:

	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(200, 200, 20, new RedCircle());//绘制红色圆形//---------------(5)

	Shape *greenCircle = new Circle(10, 100, 10, new GreenCircle());//绘制绿色圆形//-------------------(6)

	redCircle->draw();

	greenCircle->draw();
	while(1){};

	return 0;

}

运行结果：

Drawing Circle[red,radius: 20,x: 200,y: 200]
Drawing Circle[green,radius: 10,x: 10,y: 100]