Question

定义一个Shape基类，在此基础上派生出Rectangle和Cirle类，二者都有GetArea()函数计算对象的面积。使用Rec

Answer 1

#include <iostream>
using namespace std;

const double PI=3.1415926;

class Shape
{
public:
double area();
protected:
int kind;
};

double Shape::area()
{
cout<<"nothing"<<endl;
return 0;
}

class Rectangle: public Shape
{
public:
Rectangle(double a, double b);
double area();
protected:
double a, b;
};

Rectangle::Rectangle(double a, double b)
{
this->a=a;
this->b=b;
}

double Rectangle::area()
{
return a*b;
}

class Circle: public Shape
{
public:
Circle(double r);
double area();
private:
double r;
};

Circle::Circle(double r)
{
this->r=r;
}

double Circle::area()
{
return PI*r*r;
}

int main()
{
Rectangle s(4.4, 1.2);
Circle c(1.0);
cout<<"Square area= "<<s.area()<<endl;
cout<<"Circle area= "<<c.area()<<endl;
return 0;
}