Insertion in binary search tree without recursion in swift

Swift program for Insertion in binary search tree without recursion. Here more information.

import Foundation
// Swift 4 program for
// iterative insert in binary search tree
class TreeNode
{
	var data: Int;
	var left: TreeNode? ;
	var right: TreeNode? ;
	init(_ data: Int)
	{
		self.data = data;
		self.left = nil;
		self.right = nil;
	}
}
class BinarySearchTree
{
	var root: TreeNode? ;
	init()
	{
		self.root = nil;
	}
	//insert a element
	func addNode(_ data: Int)
	{
		// Create a new node
		let node: TreeNode? = TreeNode(data);
		if (self.root == nil)
		{
			// When adds a first node in bst
			self.root = node;
		}
		else
		{
			var find: TreeNode? = self.root;
			// Add new node to proper position
			while (find  != nil)
			{
				if (find!.data >= data)
				{
					if (find!.left == nil)
					{
						// When left child empty
						// So add new node here
						find!.left = node;
						return;
					}
					else
					{
						// Otherwise
						// Visit left sub-tree
						find = find!.left;
					}
				}
				else
				{
					if (find!.right == nil)
					{
						// When right child empty
						// So add new node here
						find!.right = node;
						return;
					}
					else
					{
						// Visit right sub-tree
						find = find!.right;
					}
				}
			}
		}
	}
	// Display preorder
	func preorder(_ node: TreeNode? )
	{
		if (node  != nil)
		{
			// Display node value
			print(" ",node!.data, terminator: "");
			// Visit to left subtree
			self.preorder(node!.left);
			// Visit to right subtree
			self.preorder(node!.right);
		}
	}
	func inorder(_ node: TreeNode? )
	{
		if (node  != nil)
		{
			// Visit to left subtree
			self.inorder(node!.left);
			// Display node value
			print(" ",(node!.data), terminator: "");
			// Visit to right subtree
			self.inorder(node!.right);
		}
	}
	func postorder(_ node: TreeNode? )
	{
		if (node  != nil)
		{
			// Visit to left subtree
			self.postorder(node!.left);
			// Visit to right subtree
			self.postorder(node!.right);
			// Display node value
			print(" ",(node!.data), terminator: "");
		}
	}
	static func main()
	{
		let tree: BinarySearchTree = BinarySearchTree();
		/*
		         10
		        / \
		       /   \
		      4     15
		     / \   /
		    3   5 12
		    -------------
		    Build binary search tree

		*/
		tree.addNode(10);
		tree.addNode(4);
		tree.addNode(3);
		tree.addNode(5);
		tree.addNode(15);
		tree.addNode(12);
		// Display tree nodes
		print("Preorder ");
		tree.preorder(tree.root);
		print("\nInorder ");
		tree.inorder(tree.root);
		print("\nPostorder ");
		tree.postorder(tree.root);
	}
}
BinarySearchTree.main();

Output

Preorder
  10  4  3  5  15  12
Inorder
  3  4  5  10  12  15
Postorder
  3  5  4  12  15  10


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