抽象一个形状类

#include <iostream> 
#include <iomanip> 
using namespace std; 
class Shape 
{ 
public: 
    virtual double area() const=0; 
}; 
  

class Rectangle:public Shape 
{ 
public: 
Rectangle(double r,double l):weigth(r),height(l){} 
virtual double area() const{return weigth*height;} 
protected: 
    double weigth; 
    double height;
}; 
class Triangle:public Shape 
{ 
public: 
Triangle(double r,double l):weigth(r),height(l){} 
virtual double area() const{return 0.5*weigth*height;} 
protected: 
    double weigth; 
    double height; 
}; 

  
  
int main() 
  
{ 
  
    double a,b; 
  
    cin>>a>>b;   //输入矩形的长和宽 
  
    Rectangle r(a,b);//建立Rectangle类对象r, 矩形长a宽b 
  
    Shape *s1=&r; 
  
    cout<<s1->area()<<endl;//输出矩形的面积 
  
    double w,h; 
  
    cin>>w>>h;   //输入矩形的长和宽 
  
    Triangle t(w,h); //建立Triangle类对象t，三角形底边长w高h 
  
    Shape &s2=t; 
  
    cout<<s2.area();//输出三角形面积 
  
    return 0; 
  
}