Implementing A Queue Using Array - C# Programming Exercise

// Importing necessary namespace for basic functionalities
using System; // For basic functionalities like Console

// Class that implements a Queue using an array
class Queue
{
    private int[] queueArray; // Array to hold the queue elements
    private int front;        // Index for the front of the queue
    private int rear;         // Index for the rear of the queue
    private int capacity;     // Maximum capacity of the queue
    private int size;         // Current size of the queue

    // Constructor to initialize the queue with a given capacity
    public Queue(int capacity)
    {
        this.capacity = capacity;          // Set the queue's maximum capacity
        queueArray = new int[capacity];    // Initialize the array to hold the queue elements
        front = 0;                         // Front of the queue is initially at index 0
        rear = -1;                         // Rear of the queue is initially empty
        size = 0;                          // The queue is initially empty
    }

    // Method to add an element to the queue
    public void Enqueue(int element)
    {
        if (size == capacity) // Check if the queue is full
        {
            Console.WriteLine("Queue is full! Cannot enqueue.");
            return;
        }
        rear = (rear + 1) % capacity; // Circular increment of the rear index
        queueArray[rear] = element;   // Add the new element to the rear of the queue
        size++;                       // Increase the size of the queue
        Console.WriteLine($"Enqueued: {element}");
    }

    // Method to remove an element from the queue
    public void Dequeue()
    {
        if (size == 0) // Check if the queue is empty
        {
            Console.WriteLine("Queue is empty! Cannot dequeue.");
            return;
        }
        int dequeuedElement = queueArray[front]; // Get the element at the front of the queue
        front = (front + 1) % capacity; // Circular increment of the front index
        size--; // Decrease the size of the queue
        Console.WriteLine($"Dequeued: {dequeuedElement}");
    }

    // Method to display all elements in the queue
    public void DisplayQueue()
    {
        if (size == 0) // Check if the queue is empty
        {
            Console.WriteLine("Queue is empty.");
            return;
        }

        Console.WriteLine("Queue contents:");
        int current = front;
        for (int i = 0; i < size; i++)
        {
            Console.WriteLine(queueArray[current]); // Display each element
            current = (current + 1) % capacity; // Move to the next element (circular)
        }
    }
}

// Main program to demonstrate the Queue functionality
class Program
{
    static void Main(string[] args)
    {
        // Create a queue with a capacity of 5
        Queue queue = new Queue(5);

        // Menu to allow user to interact with the queue
        while (true)
        {
            Console.WriteLine("\nMenu:");
            Console.WriteLine("1. Enqueue an element");
            Console.WriteLine("2. Dequeue an element");
            Console.WriteLine("3. Display the queue");
            Console.WriteLine("4. Exit");
            Console.Write("Enter your choice: ");
            string choice = Console.ReadLine();

            if (choice == "1")
            {
                // Prompt user to enter an element to enqueue
                Console.Write("Enter an element to enqueue: ");
                int element = int.Parse(Console.ReadLine());
                queue.Enqueue(element); // Enqueue the element
            }
            else if (choice == "2")
            {
                // Dequeue an element
                queue.Dequeue(); // Dequeue the element
            }
            else if (choice == "3")
            {
                // Display the current queue
                queue.DisplayQueue(); // Show the current elements in the queue
            }
            else if (choice == "4")
            {
                // Exit the program
                break;
            }
            else
            {
                // Invalid choice
                Console.WriteLine("Invalid choice. Please try again.");
            }
        }
    }
}