第十三周任务三

#include <iostream>using namespace std;const double pi = 3.1415926;class Shape{public:virtual double area() const = 0;};class Circle:public Shape{public:Circle(double r):rang(r){}~Circle();double area() const;private:double rang;};class Rectangle :public Shape {public:Rectangle(double l,double w):len(l),wid(w){}~Rectangle();double area() const;private:double len;double wid;};class Triangle :public Shape{public:Triangle(double d,double h):di(d),high(h){}~Triangle();double area() const;private:double di;double high;};Circle::~Circle(){}double Circle::area() const{return pi*rang*rang;}Rectangle::~Rectangle(){}double Rectangle::area() const{return len*wid;}Triangle::~Triangle(){}double Triangle::area() const{return 0.5*di*high;}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;  }