Delete a node from the end of doubly linked list in swift

Swift program for Delete a node from the end of doubly linked list. Here problem description and other solutions.

import Foundation
// Swift 4 program for
// Delete a node from the end of doubly linked list
class LinkNode
{
	var data: Int;
	var next: LinkNode? ;
	var prev: LinkNode? ;
	init(_ data: Int)
	{
		self.data = data;
		self.next = nil;
		self.prev = nil;
	}
}
class DoublyLinkedList
{
	var head: LinkNode? ;
	var tail: LinkNode? ;
	init()
	{
		self.head = nil;
		self.tail = nil;
	}
	// Insert new node at end position
	func insert(_ value: Int)
	{
		// Create a node
		let node: LinkNode = LinkNode(value);
		if (self.head == nil)
		{
			// Add first node
			self.head = node;
			self.tail = node;
			return;
		}
		// Add node at last position
		self.tail?.next = node;
		node.prev = self.tail;
		self.tail = node;
	}
	// Display node element of doubly linked list
	func display()
	{
		if (self.head == nil)
		{
			print("Empty Linked List");
		}
		else
		{
			print("\nLinked List Head to Tail :");
			// Get first node of linked list
			var temp: LinkNode? = self.head;
			// iterate linked list 
			while (temp  != nil)
			{
				// Display node value
				print("",temp!.data, terminator: " ");
				// Visit to next node
				temp = temp!.next;
			}
		}
	}
	// Remove the given node from end of linked list
	func deletionFromEnd(_ key: Int)
	{
		if (self.head == nil)
		{
			// Empty linked list
			return;
		}
		var auxiliary: LinkNode? = nil;
		var temp: LinkNode? = self.tail;
		// Find the deleted node
		while (temp  != nil && auxiliary == nil)
		{
			if (temp!.data == key)
			{
				// We found deleted node
				auxiliary = temp;
			}
			// Visit to previous node
			temp = temp!.prev;
		}
		if (auxiliary  != nil)
		{
			// When we get deleted node
			if (auxiliary!.prev  != nil)
			{
				// When previous node present
				auxiliary!.prev!.next = auxiliary!.next;
			}
			if (auxiliary!.next  != nil)
			{
				// When next node present
				auxiliary!.next!.prev = auxiliary!.prev;
			}
			if (self.head === auxiliary)
			{
				// When delete head node
				self.head = self.head!.next;
			}
			if (auxiliary === self.tail)
			{
				// When delete last node
				self.tail = self.tail!.prev;
			}
			auxiliary = nil;
		}
		else
		{
			print("\nNode not exist "
				+ String(key));
		}
	}
	static func main(_ args: [String])
	{
		let dll: DoublyLinkedList = DoublyLinkedList();
		// Insert following linked list nodes
		dll.insert(1);
		dll.insert(2);
		dll.insert(9);
		dll.insert(4);
		dll.insert(5);
		dll.insert(2);
		dll.insert(7);
		dll.insert(9);
		print("\nBefore Delete", terminator: "");
		dll.display();
		let key: Int = 2;
		dll.deletionFromEnd(key);
		print("\nAfter Delete Node "
			+ String(key), terminator: "");
		dll.display();
	}
}
DoublyLinkedList.main([String]());

Output

Before Delete
Linked List Head to Tail :
 1  2  9  4  5  2  7  9
After Delete Node 2
Linked List Head to Tail :
 1  2  9  4  5  7  9