创建三角形类

#include <iostream>

#include<math.h>

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t

private:

 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 side1;

  double  side2;

  double side3;

 public:

  Triangle(double x,double y,double z):side1(x),side2(y),side3(z){};

  double getArea() const;

     void print() const;

} ;

double Triangle::getArea() const

{

 cout<<"Triangle类的getArea函数，面积是:"<<endl;

    double p=0,q=0;

    p=((side1+side2+side3)/2);

    q=sqrt(p*(p-side1)*(p-side2)*(p-side3));

    return q;

}

void Triangle::print() const

{

 int p;

 p=(side1+side2+side3)/2;

 cout<<"Triangle:side1="<<side1<<",side2="<<side2

 <<",side3="<<side3<<",p=(side1+side2+side3)/2"<<",Area="<<sqrt(p*(p-side1)*(p-side2)*(p-side3))<<endl;

}

void creat_object(Shape **ptr);

void display_area(Shape *ptr);

void delete_object(Shape *ptr);

int main()

{

   Shape *shape_ptr;

   creat_object(&shape_ptr);

   display_area(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<<endl;

    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<<"请输入圆心的坐标和圆的半径：";

   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':

  {

   int side1,side2,side3;

   cout<<"请输入三角形的三条边长度";

   cin>>side1>>side2>>side3;

   *ptr=new Triangle(side1,side2,side3);

   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 delete_object(Shape *ptr)

{ delete(ptr);

}