几何体类

#include <iostream>using namespace std;class Shape//定义一个Shape抽象基类{public:virtual double area() =0;//公有的面积函数};class Circle:public Shape//定义Shape的子类Circle类 继承方式是公有的{public:    Circle (double r):radius(r){}        double area()    {        return radius*radius*3.1415926;//返回值为圆的面积值    }private: double radius;};class Rectangle:public Shape//定义Shape的子类Recangle类 继承方式是公有的{public:    Rectangle(double w,double h):width(w),height(h){}    double area()    {        return width*height;    }private:double width,height;};class Triangle:public Shape//定义Shape的子类Triangle类 继承方式是公有的{public:Triangle(double b,double h):base(b),height(h){}double area(){return base*height*1/2;}    private: double base,height;};int main(){    Circle c1(12.6),c2(4.9);//建立Circle类对象c1,c2,参数为圆半径    Rectangle r1(4.5,8.4),r2(5.0,2.5);//建立Rectangle类对象r1,r2,参数为矩形长、宽    Triangle t1(4.5,8.4),t2(3.4,2.8); //建立Triangle类对象t1,t2，参数为三角形底边长与高    Shape *pt[6]= {&c1,&c2,&r1,&r2,&t1,&t2}; //定义基类指针数组pt，使它每一个元素指向一个派生类对象    double areas=0.0; //areas为总面积    for(int i=0; i<6; i++)    {        areas=areas + pt[i]->area();    }    cout<<"totol of all areas="<<areas<<endl;   //输出总面积system ("pause");    return 0;}