C++继承、多态、虚函数

1	// Note:Your choice is C++ IDE #include <iostream> using namespace std; class sharpe //抽象基 { public: virtual void area()const=0;//纯虚函数 }; class rectangle:public sharpe //矩形类 { public: rectangle(double w,double l){width=w;length=l;}//构造 virtual void area()const{cout<<"矩形面积为:"<<width*length<<endl;} protected: double width,length; }; class triangle:public rectangle //三角形类 { public: triangle(double w,double l):rectangle(w,l){} virtual void area()const{cout<<"三角形的面积为:"<<width*length/2<<endl;} }; class circle:public sharpe //圆类 { public: circle(double r){radius=r;} virtual void area()const{cout<<"圆的面积为:"<<radius*radius*3.14<<endl;} protected: double radius; }; int main() { rectangle a(20,34); a.area(); triangle b(20,45); b.area(); sharpe *p=new circle(20); p->area(); delete p; return 0; }