第十三周实验报告（三）

写一个程序，定义抽象基类Shap，由他派生出的Ciecle类Rectangle类Triangle类。求出总面积。

 

#include <iostream>
using namespace std;
class Shape
{
public :
	virtual float area() =0;
};
class Circle:public Shape
{
private :
	float radius;
public :
       virtual float area ();
       Circle (float radius);
};
class Rectangle:public Shape
{
      private:
              float length;
              float wide;
      public :
      virtual float area ();
      Rectangle (float length,float wide);
};

class Triangle:public Shape
{
      private :
              float  side_length;
              float  height;
      public :
      virtual float area();
      Triangle (float side_length,float height);
};

float Circle::area()
{
      return 3.14*(radius)*(radius);
}
Circle::Circle(float radius)
{
                     this->radius=radius;
}
float Rectangle::area()
{
      return (length)*(wide);
}
Rectangle::Rectangle(float length,float wide)
{
                           this->length = length;
                           this->wide = wide;
}
float Triangle::area()
{
      return (side_length)*(height)*(0.5);
}
Triangle::Triangle(float side_lenght,float height)
{
                         this->side_length = side_lenght;
                         this-> height = 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，各元素指向一个派生类对象
	float 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;
}

 

 

 

抽象类是不能被实例化的,所以只能做基类