C++使用纯虚函数完成正方形和圆形的求面积运算。

#include <iostream>

using namespace std;

class Shape

{

public:

virtual float area()=0;

};

class Rectangle:public Shape

{

private:

float length;

float withd;

public:

Rectangle(float _l=0,float _w=0)

{

length=_l;

withd=_w;

}

float area()

{

return length*withd;

}

};

class Circle:public Shape

{

private:

float radius;

public:

Circle(float _r=0)

{

radius=_r;

}

float area()

{

return 3.14*radius*radius;

}

};

int main(int argc, const char * argv[])

{

Rectangle *rectobj;

rectobj=new Rectangle(10.23f,20.33f);

Circle *circle;

circle=new Circle(102.f);

cout<<"The rectangle area is :"<<rectobj->area()<<endl;

cout<<"The cirlce area is :"<<circle->area()<<endl;

return 0;

}