Check for continuous binary tree in swift

Swift program for Check for continuous binary tree. Here problem description and other solutions.

import Foundation
/* 
  Swift 4 program for
  Check if binary tree is continuous tree
  Using recursion
*/
// Binary Tree Node
class TreeNode
{
	var data: Int;
	var left: TreeNode? ;
	var right: TreeNode? ;
	init(_ data: Int)
	{
		// Set node value
		self.data = data;
		self.left = nil;
		self.right = nil;
	}
}
class BinaryTree
{
	var root: TreeNode? ;
	init()
	{
		self.root = nil;
	}
	func absValue(_ num: Int) -> Int
	{
		if (num < 0)
		{
			return -num;
		}
		return num;
	}
	// Check tree is continuous or not
	func isContinuous(_ node: TreeNode? ) -> Bool
	{
		if (node  != nil)
		{
			if ((node!.left  != nil && 
                 self.absValue(node!.data - node!.left!.data)  != 1) ||
              (node!.right  != nil && 
               self.absValue(node!.data - node!.right!.data)  != 1))
			{
				// Case
				// When fail continuous tree rule
				return false;
			}
			if (self.isContinuous(node!.left) && 
                self.isContinuous(node!.right))
			{
				return true;
			}
			// When node value is not satisfied
			//  continuous tree properties
			return false;
		}
		return true;
	}
	static func main()
	{
		// Create new tree
		let tree: BinaryTree = BinaryTree();
		/*  
		   Binary Tree
		   ------------
		       5
		     /   \
		    4     4
		   /     /  \
		  3     5    3
		   \
		    2
		        
		*/
		// Add tree node
		tree.root = TreeNode(5);
		tree.root!.left = TreeNode(4);
		tree.root!.right = TreeNode(4);
		tree.root!.left!.left = TreeNode(3);
		tree.root!.right!.right = TreeNode(3);
		tree.root!.right!.left = TreeNode(5);
		tree.root!.left!.left!.right = TreeNode(2);
		if (tree.isContinuous(tree.root) == true)
		{
			print("Continuous Tree ");
		}
		else
		{
			print("Not Continuous Tree ");
		}
		// Case 2
		/* 
		       5
		     /   \
		    4     4
		   /     /  \
		  3     5    3
		   \
		    1  <--- change value
		        
		*/
		tree.root!.left!.left!.right!.data = 1;
		if (tree.isContinuous(tree.root) == true)
		{
			print("Continuous Tree ");
		}
		else
		{
			print("Not Continuous Tree ");
		}
	}
}
BinaryTree.main();

Output

Continuous Tree
Not Continuous Tree