shape派生circle,rectangle,square

#include<iostream>//不正确代码。。using namespace std;const double PI=3.1415926;class shape{public:virtual double getArea(){return -1;}virtual double getPerimeter(){return -1;}};class circle:public shape{double radius;public:circle(double r=0){radius=r;}double getArea(){return PI*radius*radius;}double getPerimeter(){return 2*PI*radius;}};class rectangle:public shape{double length;double width;public:rectangle(double le=0,double wi=0){length=le;width=wi;}double getArea(){return length*width;}double getPerimeter(){return 2*width+2*length;}};class square:public rectangle{double sqlength;public:square(double sq){sqlength=sq;}double getArea(){return sqlength*sqlength;}double getPerimeter(){return 4*sqlength;}};void fun(shape* p,double *a,double *per){*a=p->getArea();*per=p->getPerimeter();}int main(){double area,perimeter;shape*pp;circle r(5);pp=&r;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;rectangle b(5,6);pp=&b;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;square c(20);pp=&c;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;}

#include <iostream>//转自http://blog.csdn.net/sxhelijian/article/details/7566500using namespace std;//定义抽象基类Shapeclass Shape{public:virtual double area() const =0;            //纯虚函数};//定义Circle类class Circle:public Shape{public:Circle(double r):radius(r){}                                     //结构函数virtual double area() const {return 3.14159*radius*radius;};   //定义虚函数protected:double radius;                                                 //半径};//定义Rectangle类class Rectangle:public Shape{public:Rectangle(double w,double h):width(w),height(h){}               //结构函数virtual double area() const {return width*height;}              //定义虚函数protected:double width,height;                                           //宽与高};class Triangle:public Shape{public:Triangle(double w,double h):width(w),height(h){}                //结构函数virtual double area() const {return 0.5*width*height;}          //定义虚函数protected:double width,height;                                            //宽与高};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system("pause");return 0;}

#include<iostream>//比较正确的写法？using namespace std;const double PI=3.1415926;class sharp{public:virtual double getArea()=0;virtual double getPerimeter()=0;};class circle:public sharp{double radius;public:circle(double r=0){radius=r;}double getArea(){return PI*radius*radius;}double getPerimeter(){return 2*PI*radius;}};class rectangle:public sharp{double length;double width;public:rectangle(double le=0,double wi=0){length=le;width=wi;}double getArea(){return length*width;}double getPerimeter(){return 2*width+2*length;}};class square:public rectangle{//double sqlength;public:square(double sq):rectangle(sq,sq){//sqlength=sq;}//double getArea()//{//return sqlength*sqlength;//}//double getPerimeter()//{//return 4*sqlength;//}};void fun(sharp* p,double *a,double *per){*a=p->getArea();*per=p->getPerimeter();}int main(){double area,perimeter;sharp *pp;circle r(5);pp=&r;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;rectangle b(5,6);pp=&b;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;square c(20);pp=&c;fun(pp,&area,&perimeter);cout<<area<<endl;cout<<perimeter<<endl;//计算圆、矩形、正方形总面积    double totalarea=0;sharp* pt[3]={&r,&b,&c};for(int i=0;i<3;i++){totalarea=totalarea+pt[i]->getArea();}cout<<totalarea<<endl;}