第十四周 【项目2-形状类族的中的纯虚函数】

#include<iostream>using namespace std;class Shape{public:    virtual double area() const =0;};class Circle:public Shape{private:    double r;public:    Circle(double rr):r(rr){};    virtual double area() const    {        return 3.14*r*r;    }};class Rectangle:public Shape{private:    double r1;    double r2;public:    Rectangle(double rr1,double rr2):r1(rr1),r2(rr2){};    virtual double area() const    {        return r1*r2;    }};class Triangle:public Shape{private:    double t1;    double t2;public:    Triangle(double tt1,double tt2):t1(tt1),t2(tt2){};    virtual double area() const    {        return t1*t2;    }};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;}

运行结果