C++ Object-Oriented Programming: Shape class and derived shapes

C++ Object oriented programming: Exercise-10 with Solution

Write a C++ program to implement a class called Shape with virtual member functions for calculating area and perimeter. Derive classes such as Circle, Rectangle, and Triangle from the Shape class and override virtual functions accordingly.

Sample Solution:

C Code:

#include <iostream> // Include necessary header for input/output stream
#include <cmath> // Include necessary header for mathematical functions

const double PI = 3.14159; // Define constant value for PI

class Shape { // Define a base class named Shape
  public:
    // Virtual member function to calculate the area (pure virtual function)
    virtual double calculateArea() const = 0;

    // Virtual member function to calculate the perimeter (pure virtual function)
    virtual double calculatePerimeter() const = 0;
};

class Circle: public Shape { // Define a derived class named Circle inheriting from Shape
  private: 
    double radius; // Private member variable to store the radius of the circle

  public:
    // Constructor for Circle class
    Circle(double rad): radius(rad) {}

    // Override the virtual member function to calculate the area
    double calculateArea() const override {
      return PI * pow(radius, 2); // Calculate the area of the circle using the radius
    }

    // Override the virtual member function to calculate the perimeter
    double calculatePerimeter() const override {
      return 2 * PI * radius; // Calculate the perimeter of the circle using the radius
    }
};

class Rectangle: public Shape { // Define a derived class named Rectangle inheriting from Shape
  private: 
    double length; // Private member variable to store the length of the rectangle
    double width; // Private member variable to store the width of the rectangle

  public:
    // Constructor for Rectangle class
    Rectangle(double len, double wid): length(len), width(wid) {}

    // Override the virtual member function to calculate the area
    double calculateArea() const override {
      return length * width; // Calculate the area of the rectangle using its length and width
    }

    // Override the virtual member function to calculate the perimeter
    double calculatePerimeter() const override {
      return 2 * (length + width); // Calculate the perimeter of the rectangle using its length and width
    }
};

class Triangle: public Shape { // Define a derived class named Triangle inheriting from Shape
  private: 
    double side1; // Private member variable to store the first side of the triangle
    double side2; // Private member variable to store the second side of the triangle
    double side3; // Private member variable to store the third side of the triangle

  public:
    // Constructor for Triangle class
    Triangle(double s1, double s2, double s3): side1(s1), side2(s2), side3(s3) {}

    // Override the virtual member function to calculate the area
    double calculateArea() const override {
      // Using Heron's formula to calculate the area of a triangle
      double s = (side1 + side2 + side3) / 2; // Calculate the semi-perimeter of the triangle
      return sqrt(s * (s - side1) * (s - side2) * (s - side3)); // Calculate the area using Heron's formula
    }

    // Override the virtual member function to calculate the perimeter
    double calculatePerimeter() const override {
      return side1 + side2 + side3; // Calculate the perimeter of the triangle using its sides
    }
};

int main() {
  // Create instances of different shapes: Circle, Rectangle, and Triangle
  Circle circle(7.0); // Create a Circle object with radius 7.0
  Rectangle rectangle(4.2, 8.0); // Create a Rectangle object with length 4.2 and width 8.0
  Triangle triangle(4.0, 4.0, 3.2); // Create a Triangle object with sides 4.0, 4.0, and 3.2

  // Calculate and display the area and perimeter of each shape
  std::cout << "Circle: " << std::endl;
  std::cout << "Area: " << circle.calculateArea() << std::endl; // Calculate and output the area of the circle
  std::cout << "Perimeter: " << circle.calculatePerimeter() << std::endl; // Calculate and output the perimeter of the circle

  std::cout << "\nRectangle: " << std::endl;
  std::cout << "Area: " << rectangle.calculateArea() << std::endl; // Calculate and output the area of the rectangle
  std::cout << "Perimeter: " << rectangle.calculatePerimeter() << std::endl; // Calculate and output the perimeter of the rectangle

  std::cout << "\nTriangle: " << std::endl;
  std::cout << "Area: " << triangle.calculateArea() << std::endl; // Calculate and output the area of the triangle
  std::cout << "Perimeter: " << triangle.calculatePerimeter() << std::endl; // Calculate and output the perimeter of the triangle

  return 0; // Return 0 to indicate successful completion
}

Sample Output:

 Circle:
Area: 153.938
Perimeter: 43.9823

Rectangle:
Area: 33.6
Perimeter: 24.4

Triangle:
Area: 5.8657
Perimeter: 11.2

Explanation:

In the above exercise,

• The Shape class is defined by two pure virtual member functions: calculateArea() and calculatePerimeter(). These functions are meant to be overridden by derived classes.
• The Circle class is derived from Shape and overrides the virtual functions to calculate the area and perimeter of a circle. This is based on the given radius.
• The Rectangle class is derived from Shape and overrides the virtual functions to calculate the area and perimeter of a rectangle. This is based on the given length and width.
• The Triangle class is derived from Shape and overrides the virtual functions to calculate the area and perimeter of a triangle. This is based on the given side lengths.
• In the main function, instances of Circle, Rectangle, and Triangle are created.
• The calculateArea() and calculatePerimeter() member functions are called on each shape object to calculate and display the respective area and perimeter.

Flowchart:

CPP Code Editor:

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