学步园

#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
class	Shape
{
public:
	virtual float area(){return 0;}
	virtual float volume(){return 0;}
	virtual void shapeName()=0;
};
class Circle:public Shape
{
public:
	Circle(float r):radius(r){}
	float area();
	void shapeName()
	{
		cout<<"Circle"<<endl;
	}
private:
	float radius;
};
float Circle::area()
{
	return 3.14*radius*radius;
}
class Rectangle:public Shape
{
public:
	Rectangle(float a,float b):l(a),w(b){}
	float area();
	void shapeName()
	{
		cout<<"Rectangle"<<endl;
	}
private:
	float l,w;
};
float Rectangle::area()
{
	return l*w;
}
class Triangle:public Shape
{
public:
	Triangle(float a,float b,float c):l(a),w(b),h(c){}
	float area();
	void shapeName()
	{
		cout<<"Triangle"<<endl;
	}
private:
	float l,w,h;
};
float Triangle::area()
{
	float t,s;
	t=(l+w+h)/2.0;
	s=sqrt(t*(t-l)*(t-w)*(t-h));
	return s;
}
int main()
{
	Shape *p;
	Circle circle(1.0);
	Rectangle rectangle(2,3);
	Triangle  	triangle(3.0,4.0,5.0);
	p=&circle;
	p->shapeName();
	cout<<p->area()<<endl;
	p=&rectangle;
	p->shapeName ();
	cout<<p->area()<<endl;
	p=▵
	p->shapeName ();
	cout<<p->area()<<endl;
	return 0;
}