题解 | #KiKi设计类继承#

#include <iostream>
using namespace std;
#include <iostream>
using namespace std;

class Shape {
  private:
    int x, y;

  public:
    Shape(int _x, int _y) : x(_x), y(_y) {}

    virtual double GetArea() const = 0;
};

class Rectangle : public Shape {
  private:
    int length, width;

  public:
    Rectangle(int _x, int _y, int _length, int _width) : Shape(_x, _y),
        length(_length), width(_width) {}

    virtual double GetArea() const {
        return length * width;
    }
};

class Circle : public Shape {
  private:
    int radius;

  public:
    Circle(int _x, int _y, int _radius) : Shape(_x, _y), radius(_radius) {}

    virtual double GetArea() const {
        return 3.14 * radius * radius;
    }
};

class Square : public Rectangle {
  public:
    Square(int _x, int _y, int _side) : Rectangle(_x, _y, _side, _side) {}
};

int main() {
    int length, width, radius, side;

    // 输入矩形的长和宽
    cin >> length >> width;
    Rectangle rectangle(0, 0, length, width);
    cout  << rectangle.GetArea() << endl;

    // 输入圆的半径
    cin >> radius;
    Circle circle(0, 0, radius);
    cout  << circle.GetArea() << endl;

    // 输入正方形的边长
    cin >> side;
    Square square(0, 0, side);
    cout  << square.GetArea() << endl;

    return 0;
}