[C++知识库]c++ 计算图形的面积

Problem Description
定义一个图形基类Shape，在此基础上派生出长方形Rectangle和圆Circle，
使用Rectangle类派生正方形类Square。计算图形的面积。
请完善下面的程序。
//你的代码将被嵌在这里
int main()
{
Shape* ps;
Rectangle* pr;

double r;
cin >> r;
ps = new Circle(r);
cout << "The area of the Circle is " << ps->getArea() << endl;
delete ps;

double l,w;
cin >> l>>w;
ps = new Rectangle(l, w);
cout << "The area of the Rectagle is " << ps->getArea() << endl;
delete ps;

double s1;
cin >> s1;
ps = new Square(s1);
cout << "The area of the Square is " << ps->getArea() << endl;
delete ps;

double s2;
cin >> s2;
pr = new Square(s2);
cout << "The area of the Square is " << pr->getArea() << endl;
delete pr;

return 0;

}

Input Description
第1个数是圆的半径
第2、3个数是长方形的长和宽
第4个数是一个正方形的边长
第5个数是另一个正方形的边长
Sample Input
1 2 3 4 5
Sample Output
The area of the Circle is 3.14
The area of the Rectagle is 6
The area of the Square is 16
The area of the Square is 25

#include <iostream>
using namespace std;
constexpr double PI = 3.14;

class Shape
{
public:
    Shape(){}//基类要有构造函数
    virtual double getArea() = 0;//纯虚函数
};

class Rectangle:public Shape
{
public:
    double x, y;
    Rectangle(double a, double b)
    {
        x = a;
        y = b;
    }
    double getArea()
    {
        return x * y;
    }
    Rectangle(){}
};


class Circle :public Shape
{
public:
    double R;
    Circle(double a)
    {
        R = a;
    }
    double getArea()
    {
        return PI * R * R;
    }
    Circle(){}
};

class Square :public Rectangle
{
public:
    double k;
    Square(double a)
    {
        k = a;
    }
    double getArea()
    {
        return k * k;
    }
    Square(){}
};

int main()
{
    Shape* ps;
    Rectangle* pr;

    double r;//圆的半径
    cin >> r;
    ps = new Circle(r);//堆区创建一块新的内存，图形基类指针维护
    cout << "The area of the Circle is " << ps->getArea() << endl;//输出圆的面积
    delete ps;//手动释放堆区新建空间

    double l, w;//长方形长，宽
    cin >> l >> w;
    ps = new Rectangle(l, w);
    cout << "The area of the Rectagle is " << ps->getArea() << endl;
    delete ps;

    double s1;
    cin >> s1;
    ps = new Square(s1);
    cout << "The area of the Square is " << ps->getArea() << endl;
    delete ps;

    double s2;
    cin >> s2;
    pr = new Square(s2);//长方形类指针指向
    cout << "The area of the Square is " << pr->getArea() << endl;
    delete pr;

    return 0;
}

#include<iostream>
#include<string.h>
#include<string>
#include<iomanip>
#include<math.h>
using namespace std;
class Shape
{
public:
    Shape(){}
    virtual double getArea() = 0;
};
class Rectangle :public Shape
{
public:
    double c, k;
    Rectangle(double a=0, double b=0)
    {
        c = a; k = b;
    }
    virtual double getArea()
    {
        return c * k ;
    }
};
class Circle :public Shape
{
public:
    double r;
    Circle(double a=0.0)
    {
        r = a;
    }
    virtual double getArea()
    {
        return 3.14 * r * r;
    }
};
class Square :public Rectangle
{
public:
    double bc;
    Square(double a)
    {
        bc = a;
    }
    virtual double getArea()
    {
        return bc * bc;
    }
};