Remove duplicates from unsorted linked list in kotlin

Kotlin program for Remove duplicates from unsorted linked list. Here problem description and explanation.

// Kotlin Program for 
// Delete duplicate nodes in unsorted linked list
class LinkNode
{
	var data: Int;
	var next: LinkNode ? ;
	constructor(data: Int)
	{
		this.data = data;
		this.next = null;
	}
}
class LinkedList
{
	var head: LinkNode ? ;
	var tail: LinkNode ? ;
	// Class constructors
	constructor()
	{
		this.head = null;
		this.tail = null;
	}
	// Insert new element at end position
	fun insert(value: Int): Unit
	{
		// Create new node
		val node: LinkNode = LinkNode(value);
		if (this.head == null)
		{
			// Add first node
			this.head = node;
		}
		else
		{
			// Add new node at the last position
			this.tail?.next = node;
		}
		// Make new tail 
		this.tail = node;
	}
	// Display all node value
	fun display(): Unit
	{
		if (this.head != null)
		{
			print("Linked List Element :");
			var temp: LinkNode ? = this.head;
			while (temp != null)
			{
				// Display node value
				print("  " + temp.data);
				// Visit to next node
				temp = temp.next;
			}
		}
		else
		{
			println("Empty Linked list");
		}
	}
	fun removeNode(): Unit
	{
		if (this.head == null)
		{
			// When linked list empty
			print("Empty Linked list");
		}
		else
		{
			// Auxiliary variable
			var temp: LinkNode ? = this.head;
			var hold: LinkNode ? = null;
			var initial: LinkNode ? ;
			var current: LinkNode ? ;
			// Outer loop
			while (temp != null)
			{
				this.tail = temp;
				current = temp;
				initial = current.next;
				// Inner loop
				// Remove all node which value is similar to temp node
				while (initial != null)
				{
					if (temp.data == initial.data)
					{
						// Get remove node
						hold = initial;
					}
					else
					{
						current = initial;
					}
					// Visit to next node
					initial = initial.next;
					if (hold != null)
					{
						current?.next = initial;
						// remove node
						hold = null;
					}
				}
				// Visit to next node
				temp = temp.next;
			}
		}
	}
}
fun main(args: Array < String > ): Unit
{
	// new linked list
	val task: LinkedList = LinkedList();
	// Add tested element
	task.insert(1);
	task.insert(2);
	task.insert(9);
	task.insert(4);
	task.insert(9);
	task.insert(3);
	task.insert(1);
	task.insert(7);
	task.insert(2);
	task.insert(1);
	println("\nBefore Delete ");
	task.display();
	task.removeNode();
	println("\nAfter Delete ");
	task.display();
}

Output

Before Delete
Linked List Element :  1  2  9  4  9  3  1  7  2  1
After Delete
Linked List Element :  1  2  9  4  3  7


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