项目2-形状类族中的纯虚函数

项目2-形状类族的中的纯虚函数

写一个程序，定义抽象基类Shape，由它派生出3个派生类，Circle（圆形）、Rectangle（矩形）、Triangle（三角形）。用例如以下的main()函数。求出定义的几个几何体的面积和。 

int main()
{
    Circle c1(12.6),c2(4.9);//建立Circle类对象c1,c2,參数为圆半径
    Rectangle r1(4.5,8.4),r2(5.0,2.5);//建立Rectangle类对象r1,r2,參数为矩形长、宽
    Triangle t1(4.5,8.4),t2(3.4,2.8); //建立Triangle类对象t1,t2，參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;
}

 

#include <iostream>
using namespace std;
class Shape
{
public:
    virtual double area()=0;
};
class Circle:public Shape
{
public:
    Circle(double r):radius(r) {}
    virtual double area()
    {
        return 3.14159*radius*radius;
    };
protected:
    double radius;
};
class Rectangle:public Shape
{
public:
    Rectangle(double w,double h):width(w),height(h) {}
    virtual double area()
    {
        return width*height;
    }
protected:
    double width,height;
};

class Triangle:public Shape
{
public:
    Triangle(double w,double h):width(w),height(h) {}
    virtual double area()
    {
        return 0.5*width*height;
    }
protected:
    double width,height;
};

int main()
{
    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;
    return 0;
}