[数据结构与算法]C++：抽象类和虚函数示例

#pragma once
//Shape类为抽象类
const double PI = 3.14;
class Shape
{
public:
	//Shape();
	//~Shape();
	virtual double GetArea()=0;		   //纯虚函数，计算面积
	virtual double GetPerimeter() = 0;		//纯虚函数，计算周长
};

#pragma once
#include "Shape.h"
class Circle :	public Shape	//继承自Shape类
{
public:
	Circle(int nR);
	~Circle();
	double GetArea();		   //计算面积
	double GetPerimeter();		//计算周长
private:
	double m_nR;		//半径
};

#include "stdafx.h"
#include "Circle.h"


Circle::Circle(int nR)
{
	m_nR = nR;
}


Circle::~Circle()
{
}

double Circle::GetArea()		   //计算面积
{
	return PI * m_nR * m_nR;
}
double Circle::GetPerimeter()		//计算周长
{
	return 2 * PI * m_nR;
}

#pragma once
#include "Shape.h"
class Rectangle :public Shape//类的继承
{
public:
	Rectangle(double nLength, double nWidth);
	~Rectangle();
	double GetArea();		   //计算面积
	double GetPerimeter();		//计算周长
private:
	double m_nLength, m_nWidth;	//长，宽
};

#include "stdafx.h"
#include "Rectangle.h"


Rectangle::Rectangle(double nLength, double nWidth)
{
	m_nLength = nLength;
	m_nWidth = nWidth;
}


Rectangle::~Rectangle()
{
}

double Rectangle::GetArea()		   //计算面积,重定义
{
	return m_nLength*m_nWidth;
}
double Rectangle::GetPerimeter()		//计算周长,重定义
{
	return 2 * (m_nLength + m_nWidth);
}

// ClassExampleVirtual2.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "Shape.h"
#include"Circle.h"
#include "Rectangle.h"
#include <iostream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	int r = 3;	//圆的半径
	int a = 8, b = 5;	//矩形的长和宽
	Circle circle(r);	//
	Rectangle 	rectangle(8, 5);
	cout << "圆的面积为：" << circle.GetArea() << endl
		<< "圆的周长为：" << circle.GetPerimeter() << endl
		<< "矩形的面积为" << rectangle.GetArea() << endl
		<< "矩形的周长为：" << rectangle.GetPerimeter() << endl;
	getchar();
	return 0;
}

运行结果：

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