7、形狀（一）

編寫C++程序完成以下功能：

（1）    聲明一個基類Shape（形狀），其中包含一個方法來計算面積；

（2）    從Shape派生兩個類矩形和圓形；

（3）    從矩形派生正方形；

（4）    分別實現(xiàn)派生類構(gòu)造函數(shù)、析構(gòu)函數(shù)和其他方法；

（5）    創(chuàng)建派生類的對象，觀察構(gòu)造函數(shù)、析構(gòu)函數(shù)調(diào)用次序；

（6）    不同對象計算面積。

#include<iostream>

#define PI 3.1415

using namespace std;

class Shape

{

public:

                   Shape() {cout<<"調(diào)用構(gòu)造函數(shù)Shape"<<endl;}

                   ~Shape() {cout<<"調(diào)用析構(gòu)函數(shù)Shape"<<endl;}

                   double Girth() {}

                   double Area() {}

};

class Rectangle: public Shape

{

private:

                   double len;

                   double wide;

public:

                   Rectangle(double l=0,double w=0) {len=l; wide=w; cout<<"調(diào)用構(gòu)造函數(shù)Rectangle"<<endl;}

                   void SetRectangle(double l=0,double w=0) {len=l; wide=w;}

                   ~Rectangle(){cout<<"調(diào)用析構(gòu)函數(shù)Rectangle"<<endl;}

                   double Girth() {return (len+wide)*2;}

                   double Area() {return len*wide;}

};

class Circle:public Shape

{

private:

                   double r;

public:

                   Circle(double radius=0) {r=radius; cout<<"調(diào)用構(gòu)造函數(shù)Circle"<<endl;}

    void SetCircle(double radius=0) {r=radius;}

                   ~Circle(){cout<<"調(diào)用析構(gòu)函數(shù)Circle"<<endl;}

                   double Girth() {return 2*PI*r;}

                   double Area() {return PI*r*r;}

};

class Square:public Rectangle

{

public:

                   Square(double x=0) {Rectangle(x,x); cout<<"調(diào)用構(gòu)造函數(shù)Square"<<endl;}

    void SetSquare(double x=0) {SetRectangle(x,x);}

                   ~Square(){cout<<"調(diào)用析構(gòu)函數(shù)Square"<<endl;}

};

int main()

{

                   Rectangle b;

                   Circle c;

                   Square d;

                   double x,y,m,n;

                   cout<<endl<<"請輸入矩形長和寬（用空格隔開）："<<endl;

                   cin>>x>>y;

                   b.SetRectangle(x,y);

                   cout<<"矩形周長為："<<b.Girth()<<endl;

                   cout<<"矩形面積為："<<b.Area()<<endl;

    cout<<endl<<"請輸入圓形的半徑："<<endl;

                   cin>>m;

                   c.SetCircle(m);

                   cout<<"圓形周長為："<<c.Girth()<<endl;

                   cout<<"圓形面積為："<<c.Area()<<endl;

    cout<<endl<<"請輸入正方形的邊長："<<endl;

                   cin>>n;

                   d.SetSquare(n);

                   cout<<"正方形周長為："<<d.Girth()<<endl;

                   cout<<"圓形面積為："<<d.Area()<<endl;

                   system("pause");

                   cout<<endl;

                   return 0;

}