十三周任务一

#include<iostream>
using namespace std;

class Shape                 //定义虚基类
{
public:
	virtual double area() const = 0;   //定义纯虚函数
};

class Circle: public Shape
{
public:
	Circle(double radius)    //老师推荐这样初始化
	{
		this->radius = radius;
	}
	virtual double area() const
	{
		return ( 3.14 * radius * radius);
	}
protected:
	double radius;
};

class Rectangle:public Shape
{
public:
   	Rectangle(double width,double height)     //老师推荐这样初始化
	{
		this->width = width;
		this->height = height;
	}
	virtual double area() const
	{
		return ( width * height );
	}
protected:
	double width;
	double height;
};

class Triangle: public Shape
{
public:
	Triangle(double width,double height)    //老师推荐这样初始化
	{
		this->width = width;
		this->height = height;
	}
	virtual double area() const
	{
		return (0.5 * width * height);
	}
protected:
	double width;
	double height;
};

int main()                      //定义主函数
{
	Circle c1(12.6),c2(4.9);
	Rectangle r1(4.5,8.4),r2(5.0,2.5);
	Triangle t1(4.5,8.4),t2(3.4,2.8);
	Shape *pt[6] = {&c1,&c2,&r1,&r2,&t1,&t2};
	double areas = 0.0;
	for(int i = 0;i < 6;i++)
	{
		areas = areas + pt[i]->area();
	}
	cout << "totol of all areas = " << areas << endl;
	system("pause");
	return 0;
}