Rectangle矩形类

/*矩形类*/
class Rectangle
{
private:
	double L = 0;
	double W = 0;
public:
	Rectangle() = default;
	Rectangle(double a, double b);
	double GetArea();	/*矩形面积*/
	double GetGirth();	/*矩形周长*/
};
/*构造函数*/
Rectangle::Rectangle(double a, double b) : L{ a }, W{ b } {}
/*矩形面积*/
double Rectangle::GetArea()
{
	double S = L * W;
	return S;
}
/*矩形周长*/
double Rectangle::GetGirth()
{
	double L = 2 * (this->L + W);
	return L;
}

Cuboid长方体类

/*长方体类*/
class Cuboid : public Rectangle 
{
private:
	double H = 0;
public:
	Cuboid() = default;
	Cuboid(double a, double b, double c);
	double GetVolume();        /*长方体体积*/
	double GetSurfaceArea();   /*长方体表面积*/
};
/*构造函数*/
Cuboid::Cuboid(double a, double b, double c) : Rectangle{ a,b }, H{ c } {}
/*长方体体积*/
double Cuboid::GetVolume()
{
	double V = H * GetArea();
	return V;
}
/*长方体表面积*/
double Cuboid::GetSurfaceArea()
{
	double S = 2 * GetArea() + H * GetGirth();
	return S;
}

测试：

#include "Rectangle.h"

#include <iostream>
using namespace std;

int main(void)
{
	Rectangle Re{ 4,4 };
	cout << "矩形面积：" << Re.GetArea() << endl;
	cout << "矩形周长：" << Re.GetGirth() << endl;
	Cuboid Cu{ 3,3,3 };
	cout << "底面积：" << Cu.GetArea() << endl;
	cout << "体积：" << Cu.GetVolume() << endl;
	cout << "底周长：" << Cu.GetGirth() << endl;
	cout << "表面积：" << Cu.GetSurfaceArea() << endl;
	return 0;
}

测试结果：