习题 12.5 写一个程序，定义抽象基类Shape，由它派生出5个派生类：Circle、Square、Rectangle、Tarpezoid、Triangle。用虚函数分别计算几种图形面积，并求。。。

深碍√TFBOYSˉ_ 2022-05-10 02:06 470阅读 0赞

### C++程序设计（第三版） 谭浩强 习题12.5 个人设计 ###

#### 习题 12.5 写一个程序，定义抽象基类Shape，由它派生出5个派生类：Circle、Square、Rectangle、Tarpezoid、Triangle。用虚函数分别计算几种图形面积，并求它们的和。要求用基类指针数组，使它的每一个元素指向一个派生类对象。 ####

代码块：

#include <iostream>
    #include <iomanip>
    using namespace std;
    class Shape
    {
    public:
    	Shape(){}
    	virtual ~Shape(){}
    	virtual double Area() const{return 0;}
    	virtual void shapeName() const =0;
    };
    class Circle: public Shape
    {
    public:
    	Circle(double r){radius=r;}
    	~Circle(){}
    	virtual double Area() const {return 3.14159*radius*radius;}
    	virtual void shapeName() const {cout<<"Circle ";}
    protected:
    	double radius;
    };
    class Square: public Shape
    {
    public:
    	Square(double a){x=a;}
    	~Square(){}
    	virtual double Area() const {return x*x;}
    	virtual void shapeName() const {cout<<"Square ";}
    protected:
    	double x;
    };
    class Rectangle: public Shape
    {
    public:
    	Rectangle(double a, double b){x=a; y=b;}
    	~Rectangle(){}
    	virtual double Area() const {return x*y;}
    	virtual void shapeName() const {cout<<"Rectangle ";}
    protected:
    	double x, y;
    };
    class Trapezoid: public Shape
    {
    public:
    	Trapezoid(double a, double b, double c){x=a; y=b; z=c;}
    	~Trapezoid(){}
    	virtual double Area() const{return ((x+y)*z)/2;}
    	virtual void shapeName() const {cout<<"Trapezoid ";}
    protected:
    	double x, y, z;
    };
    class Triangle: public Shape
    {
    public:
    	Triangle(double a, double h){x=a; y=h;}
    	~Triangle(){}
    	virtual double Area() const {return (x*y)/2;}
    	virtual void shapeName() const {cout<<"Triangle ";}
    protected:
    	double x, y;
    };
    int main()
    {
    	Circle circle(5);
    	Square square(4);
    	Rectangle rectangle(3, 4);
    	Trapezoid trapezoid(2.0, 3.0, 4.0);
    	Triangle triangle(4, 3);
    	double sum=0;
    	Shape *pt[5]={&circle, &square, &rectangle, &trapezoid, &triangle};
    	Shape **p;
    	for (p=pt; p<pt+5; p++){
    		(*p)->shapeName();
    		cout<<"area="<<(*p)->Area()<<endl;
    		sum+=(*p)->Area();
    	}
    	cout<<"Area sum="<<sum<<endl;
    	system("pause");
    	return 0;
    }