14周 项目2 形状类族中的纯虚函数

#include <iostream>

using namespace std;

class Shape
{
public:
    virtual double area()=0;
};
class Circle:public Shape
{
public:
    Circle(double r):R(r) {}
    virtual double area()
    {
        return R*R*3.14;
    }
protected:
    double R;
};
class Rectangle:public Shape
{
public:
    Rectangle(double l,double w):length(l),weight(w) {}
    virtual double area()
    {
        return length*weight;
    }
protected:
    double length;
    double weight;
};
class Triangle:public Shape
{
public:
    Triangle(double h,double b):base(b),height(h) {}
    virtual double area()
    {
        return 0.5*base*height;
    }
protected:
    double base;
    double 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
    return 0;
}

14周 项目2 形状类族中的纯虚函数