十三周任务3

#include<iostream>      #include<Cmath>      using namespace std;  const double pi=3.1415926;    class Shape //定义抽象基类   {  public:      virtual double areas()=0;  };      class Circle: public Shape   //利用抽象基类定义圆类      {    public:        Circle(double Circle_radius);//构造函数          ~Circle(){}       double areas();  private:        double Circle_radius;    };   class Rectangle: public Shape    //利用抽象基类定义矩形类        {    public:        Rectangle(double Rectangle_long,double Rectangle_wide);//构造函数          ~Rectangle(){}        double areas();    private:        double Rectangle_long;        double Rectangle_wide;    };     class Triangle: public Shape  //利用抽象基类定义三角形类      {    public:        Triangle(double Triangle_bottom,double Triangle_high); //构造函数          ~Triangle(){}        double areas();   private:        double Triangle_bottom;      double Triangle_high;    };  Circle::Circle(double Circle_radius)//构造函数   {      this->Circle_radius=Circle_radius;  }  double Circle::areas()  {  return (pi*Circle_radius*Circle_radius);  }  Rectangle::Rectangle(double Rectangle_long,double Rectangle_wide)  {      this->Rectangle_long=Rectangle_long;      this->Rectangle_wide=Rectangle_wide;  }  double Rectangle::areas()  {      return (Rectangle_long*Rectangle_long);  }  Triangle::Triangle(double Triangle_bottom,double Triangle_high)  {      this->Triangle_bottom=Triangle_bottom;      this->Triangle_high=Triangle_high;  }  double Triangle::areas()   {      return (Triangle_bottom*Triangle_high/2);  }    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，各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]->areas();      }      cout<<"totol of all areas="<<areas<<endl;   //输出总面积       system("pause");      return 0;  }