QueueThroughLinkedList_C#

// C# program for linked-list
// implementation of queue
using System;

// A linked list (LL) node to
// store a queue entry
class QNode {
	public int key;
	public QNode next;

	// constructor to create
	// a new linked list node
	public QNode(int key)
	{
		this.key = key;
		this.next = null;
	}
}

// A class to represent a queue The queue,
// front stores the front node of LL and
// rear stores the last node of LL
class Queue {
	public QNode front, rear;

	public Queue() { this.front = this.rear = null; }

	// Method to add an key to the queue.
	public void enqueue(int key)
	{

		// Create a new LL node
		QNode temp = new QNode(key);

		// If queue is empty, then new
		// node is front and rear both
		if (this.rear == null) {
			this.front = this.rear = temp;
			return;
		}

		// Add the new node at the
		// end of queue and change rear
		this.rear.next = temp;
		this.rear = temp;
	}

	// Method to remove an key from queue.
	public void dequeue()
	{
		// If queue is empty, return NULL.
		if (this.front == null)
			return;

		// Store previous front and
		// move front one node ahead
		this.front = this.front.next;

		// If front becomes NULL,
		// then change rear also as NULL
		if (this.front == null)
			this.rear = null;
	}
}

// Driver code
public class Test {
	public static void Main(String[] args)
	{
		Queue q = new Queue();
		q.enqueue(10);
		q.enqueue(20);
		q.dequeue();
		q.dequeue();
		q.enqueue(30);
		q.enqueue(40);
		q.enqueue(50);
		q.dequeue();
		Console.WriteLine("Queue Front : " + ((q.front != null) ? (q.front).key : -1));
		Console.WriteLine("Queue Rear : " + ((q.rear != null) ? (q.rear).key : -1));
	}
}

// This code has been contributed by Rajput-Ji