扩展程序：创建一个三角形类

//扩展程序：创建一个三角形类//修改create_object函数，使得程序支持三角形的创建//和求面积、打印等操作#include <iostream>#include "cmath"using namespace std;class Shape {public:virtual double getArea() const =0;virtual void print() const =0;  virtual ~Shape(){}}; class Circle : public Shape {public:Circle( int = 0, int = 0, double = 0.0 );  virtual double getArea() const;   // 返回面积virtual void print() const;  // 输出Circle 类对象tprivate: int x,y;        // 圆心座标double radius;  // 圆半径}; // 派生类Circle定义结束class Rectangle : public Shape {public:Rectangle( int = 0, int = 0);  // 构造函数virtual double getArea() const;   // 返回面积void print() const;  // 输出Rectangle类对象protected:int a,b;       // 矩形的长和宽}; // 派生类double Shape::getArea() const{    cout<<"基类的getArea函数，面积是 ";   return 0.0;}  // Shape类getArea函数的定义void Shape::print() const{cout<<"Base class Object"<<endl;}//Shape类print函数定义Circle::Circle( int xValue, int yValue, double radiusValue ){x=xValue;  y=yValue;radius= radiusValue ;} // Circle类构造函数double Circle::getArea() const{   cout<<"Circle类的getArea函数，面积是 ";      return 3.14159 * radius * radius;} // Circle类getArea函数定义void Circle::print() const{   cout << "center is ";   cout<<"x="<<x<<"   y="<<y;   cout << "; radius is " << radius<<endl;} // Circle类print函数定义Rectangle::Rectangle( int aValue, int bValue ){a=aValue;  b=bValue;} // Rectangle类构造函数double Rectangle::getArea() const{   cout<<"Rectangle类的getArea函数，面积是 ";      return a * b;}       // Rectangle类getArea函数定义void Rectangle::print() const{   cout << "hight is "<<a;   cout<<"width is"<<b<<endl;} class Cube : public Rectangle {//派生类Cube的定义public:Cube(int x=0, int y=0, int z=0):Rectangle(x,y),c(z){};double getArea() const;void print() const; private:int c;}; double Cube::getArea() const{return a*b*c;}void Cube::print() const{cout<<"Cube:h="<<c<<",length="<<a<<",width="<<b<<",Area="<<a*b*c<<endl;}class Triangle : public Shape{protected:double x, y, z;public:Triangle(double a = 0, double b = 0, double c = 0):x(a), y(b), z(c){}double getArea() const;void print() const;};void Triangle::print() const{cout << "Triangle:x = " << x << ",y =" << y << ",z =" << z << endl;}double Triangle::getArea() const{double len = x + y + z;double p = len / 2;double s = sqrt(p*(p - x)*(p - y)*(p - z));cout<<"Triangle类的getArea函数，面积是 ";return s;}void creat_object(Shape **ptr);void display_area(Shape *ptr);void display_side(Shape *ptr);void delete_object(Shape *ptr);int main(){   Shape *shape_ptr;   creat_object(&shape_ptr);   display_area(shape_ptr);   display_side(shape_ptr);   delete_object(shape_ptr);return 0;}void creat_object(Shape **ptr){char type;*ptr = NULL;//空指针do{   cout<<"创建对象。请选择：";   cout<<"c:Circle类对象；r:Rectangle类对象；u:Cube类对象; t:Triangle类对象"<<endl;   cin>>type;       switch (type)   {case 'c'://创建Ciecle类对象{int xx,yy; double rr; cout<<"请输入圆心的座标和圆的半径："; cin>>xx>>yy>>rr; *ptr = new Circle(xx,yy,rr); break;}  case 'r'://创建Rectangle类对象 {int aa,bb; cout<<"请输入矩形的长和宽："; cin>>aa>>bb; *ptr = new Rectangle(aa,bb); break;}  case 'u'://创建Cube类对象 {int aa,bb,cc; cout<<"请输入立方体的长、宽、高："; cin>>aa>>bb>>cc; *ptr = new Cube(aa,bb,cc); break;}case 't':{double x, y, z;cout << "请输入三角形的三条边：";cin >> x >> y >> z;*ptr = new Triangle(x, y, z);break;}    default:cout<<"类型错误，请重新选择\n";   }   }while(*ptr==NULL);} void display_area(Shape *ptr){   cout<<"显示所创建对象的面积，调用的是"<<endl;    cout<<ptr->getArea() << endl;}void display_side(Shape *ptr){cout << "显示所创建对象的边：" << endl;ptr -> print();}void delete_object(Shape *ptr){delete(ptr);}<img src="http://img.blog.csdn.net/20150519205905306" alt="" />