编写一个程序计算三角-正方形及圆形面积.doc

1、编写一个程序计算三角，正方形和圆形的面积。
分析：依题意，可以抽象出一个基类CBase，在其中说明一个虚函数，用来求面积，并利用单接口、多实现版本设计各个图形求面积的方法。
#include<iostream>
#include<math.h>
#define PI 3.14159
using namespace std;

class Shape{
public:
virtual double getArea() = 0;
protected:
double area;
};

class Triangle:public Shape{
public:
Triangle(double a,double b,double c){
this->a = a;
this->b = b;
this->c = c;
}
virtual double getArea(){
double p = (a+b+c)/2;
this->area = sqrt(p*(p-a)*(p-b)*(p-c));
return this->area;
}
private:
double a;
double b;
double c;
};

class Rectangle:public Shape{
public:
Rectangle(double width,double height){
this->width = width;
this->height = height;
}
virtual double getArea(){
this->area = this->width*this->height;
return this->area;
}
private:
double width;
double height;
};

class Circle:public Shape{
public:
Circle(double radius){
this->radius = radius;
}
virtual double getArea(){
this->area = PI*radius*radius;
return this->area;
}
private:
double radius;
};

int main(){
Shape *pTg = new Triangle(3.0,4.0,5.0);
Shape *pRtg = new Rectangle(4.0,5.0);
Shape *pCle = new Circle(5.0);
cout<<"Area of Triangle is "<<pTg->getArea()<<endl;
cout<<"Area of Rectangle is "<<pRtg->getArea()<<endl;
cout<<"Area of Circle is "<<pCle->getArea()<<endl;
system("pause");
return 0;
}