题目:7-5 定义一个Shape基类,在此基础上派生出Rectangle和Circle,二者都有GetArea()函数计算对象的面积。使用Rectangle类创建一个派生类Square。
#include <iostream>
#define pi 3.14
using namespace std;
class Shape
{
public:
Shape(){}
~Shape(){}
virtual double GetArea() { return -1; }
};
class Circle:public Shape
{
public:
Circle(double radius):itsRadius(radius){}
~Circle(){}
double GetArea() { return pi * itsRadius * itsRadius; }
private:
double itsRadius;
};
class Rectangle : public Shape
{
public:
Rectangle(double len,double width):itsLength(len),itsWidth(width){};
~Rectangle(){};
virtual double GetArea() { return itsLength * itsWidth; }
virtual double GetLength() { return itsLength; }
virtual double GetWidth() { return itsWidth; }
private:
double itsWidth;
double itsLength;
};
class Square:public Rectangle
{
public:
Square(float len);
~Square(){}
};
Square::Square(float len):Rectangle(len,len){}
int main()
{
Shape * sp;
sp = new Circle(1);
cout << "区域的周长为: " << sp->GetArea () << endl;
delete sp;
sp = new Rectangle(4,5);
cout << "矩形的面积为: " << sp->GetArea() << endl;
delete sp;
sp = new Square(1);
cout << "区域的面积为: " << sp->GetArea() << endl;
delete sp;
return 0;
}