Delete a node from linked list specific position in kotlin

Kotlin program for Delete a node from linked list specific position. Here problem description and explanation.

// Kotlin Program for
// Delete node at given index of linked list

// Linked list node
class LinkNode
{
	var data: Int;
	var next: LinkNode ? ;
	constructor(data: Int)
	{
		this.data = data;
		this.next = null;
	}
}
class SingleLL
{
	var head: LinkNode ? ;
	var tail: LinkNode ? ;
	constructor()
	{
		this.head = null;
		this.tail = null;
	}
	// Add new node at the end of linked list
	fun addNode(value: Int): Unit
	{
		// Create a new node
		val node: LinkNode = LinkNode(value);
		if (this.head == null)
		{
			this.head = node;
		}
		else
		{
			this.tail?.next = node;
		}
		this.tail = node;
	}
	// Display linked list element
	fun display(): Unit
	{
		if (this.head == null)
		{
			return;
		}
		var temp: LinkNode ? = this.head;
		// iterating linked list elements
		while (temp != null)
		{
			print(""+ temp.data + " → ");
			// Visit to next node
			temp = temp.next;
		}
		println("NULL");
	}
	// Delete node at given position
	fun deleteAtIndex(index: Int): Unit
	{
		var temp: LinkNode ? = this.head;
		if (this.head == null)
		{
			println("Empty linked list");
			return;
		}
		else if (index < 0)
		{
			println("Invalid positions");
			return;
		}
		else if (index == 1)
		{
			// Means deleting a first node
			if (this.tail == this.head)
			{
				// Only one node
				this.tail = null;
			}
			// Make second node as head
			this.head = this.head?.next;
		}
		else
		{
			var count: Int = index - 1;
			// iterating linked list elements and find deleted node
			while (temp != null && count > 1)
			{
				// Visit to next node
				temp = temp.next;
				count -= 1;
			}
			if (count == 1 && temp?.next != null)
			{
				// Get deleted node
				val n: LinkNode? = temp.next;
				if (n == this.tail)
				{
					// When delete last node
					this.tail = temp;
				}
				// Unlink the deleting node
				temp.next = n?.next;
			}
			else
			{
				println(" Index " + index + " are not present");
				return;
			}
		}
	}
}
fun main(args: Array < String > ): Unit
{
	val sll: SingleLL = SingleLL();
	// Test with your index
	// Note index start with 1
	val index: Int = 5;
	// Linked list
	// 10 → 20 → 30 → 40 → 50 → 60 → 70 → 80 → NULL
	sll.addNode(10);
	sll.addNode(20);
	sll.addNode(30);
	sll.addNode(40);
	sll.addNode(50);
	sll.addNode(60);
	sll.addNode(70);
	sll.addNode(80);
	println(" Before Delete Linked List");
	sll.display();
	// Delete node at 5-th position
	sll.deleteAtIndex(index);
	// Display linked list
	println(" After Delete Linked List");
	sll.display();
}

Output

 Before Delete Linked List
10 → 20 → 30 → 40 → 50 → 60 → 70 → 80 → NULL
 After Delete Linked List
10 → 20 → 30 → 40 → 60 → 70 → 80 → NULL