C++ 纯虚函数和抽象类 实现shape类

#include <iostream>
using namespace std;
const double PI = 3.1415926;
class Shape
{
public:
	virtual double getArea() const = 0;
	Shape() {}
	~Shape() {}
};
class Rectangle :public Shape {
public:
	Rectangle() { length = 0.0; width = 0.0; }
	~Rectangle() {}
	Rectangle(double length, double width) :length(length), width(width) {}
	virtual double getArea() const{
		return length * width;
	}
private:
	double length, width;
};

class Circle :public Shape {
public:
	Circle() { radius = 0.0; }
	Circle(double radius) :radius(radius) {}
	~Circle() {}
	virtual double getArea() const{
		return radius * PI * radius;
	}
private:
	double radius;
};
class Total {
public:
	Total(Shape* shape1, Shape* shape2) :shape1(shape1), shape2(shape2) {}
	double sumArea() {
		return shape1->getArea() + shape2->getArea();
	}
private:
	Shape* shape1;
	Shape* shape2;
};
int main()
{
	Rectangle r(3.0 ,2.0);
	Circle c(1.0);
	Total t(&r, &c);

    std::cout << t.sumArea();

}