第十三周实验报告三

<span style="font-size:16px;">#include<iostream>

using namespace std;

const double PI = 3.14159;

class Shape
{
public:
virtual double area() const =0;    //定义纯虚函数，供派生类使用
};

class Circle: public Shape
{
public:
Circle(double radius);
virtual double area() const;
protected:
double radius;                                                 //半径
};

class Rectangle: public Shape
{
public:
Rectangle(double length, double width);
virtual double area() const;
protected:
double length;
double width;
};

class Triangle: public Shape
{
public:
Triangle(double base, double height);
virtual double area() const;
protected:
double base;
double height;
};

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

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

Rectangle::Rectangle(double length, double width)
{
this->length = length;
this->width = width;
}

double Rectangle::area() const
{
return length * width;
}

Triangle::Triangle(double base, double height)
{
this->base = base;
this->height = height;
}

double Triangle::area() const
{
return 0.5 * base * height;
}

int main()
{
Circle c1(12.6), c2(4.9);    //建立Circle类对象c1,c2,参数为圆半径
Rectangle r1(4.5, 8.4), r2(5.0, 2.5);       //建立Rectangle类对象r1,r2,参数为矩形长、宽
Triangle t1(4.5, 8.4), t2(3.4, 2.8);    //建立Triangle类对象t1,t2，参数为三角形底边长与高
Shape *pt[6] = {&c1, &c2, &r1, &r2, &t1, &t2}; //定义基类指针数组pt，各元素指向一个派生类对象

double areas = 0.0;      //areas为总面积

for(int i = 0; i < 6; i++)
{
areas = areas + pt[i]->area();
}

cout << "totol of all areas=" << areas << endl;   //输出总面积

system("pause");
return 0;
}
</span>