shape类

定义一个shape类，在此基类基础上派生Rectangele 和circle类，二者都有getarea()函数计算对象的面积，使用Rectangele 类创建一个派生类square类。请设计各个类并进

#include<iostream>
using namespace std;
class shape
{
public:
 virtual double getarea()=0;

};
class Rectangele:public shape
{
private:
 double longth;
 double width;
public:
Rectangele(double a,double b)
{
 longth=a;
 width=b;
}
~Rectangele()
{cout<<"Rectangele释放"<<endl;}
double getarea()
{return longth*width;}
};
class circle:public shape
{
private:
 double r;
public:
 circle(double a)
 {r=a;}
 ~circle()
 {cout<<"circle释放"<<endl;}
 double getarea()
 {return 3.14*r*r;}
};
class square:public shape
{
private:
 double a;
public:
 square(double aa)
 {a=aa;}
 ~square()
 {cout<<"square释放"<<endl;}
 double getarea()
 {return a*a;}

};
void main()
{
 Rectangele A(1,2);
 cout<<A.getarea()<<endl;
 circle B(2);
 cout<<B.getarea()<<endl;
 square C(3);
 cout<<C.getarea()<<endl;
}