14.2

#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();    private:    double R;};double Circle::area(){    return(3.14*R*R);}class Recentangle:public Shape{    public:    Recentangle(double l,double w):length(l),width(w){}    virtual double area();    private:    double length;    double width;};double Recentangle::area(){    return(length*width);}class Triangle:public Shape{    public:    Triangle(double l,double w):length(l),width(w){}    virtual double area();    private:    double length;    double width;};double Triangle::area(){    return(length*width/2);}int main(){    Circle c1(12.6),c2(4.9);//建立Circle类对象c1,c2,参数为圆半径    Recentangle 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;}