Find the balanced node of linked list in swift

Swift program for Find the balanced node of linked list. Here problem description and explanation.

import Foundation
/*
  Swift 4 program for
  Find the balanced node in a linked list
*/
// Node of LinkedList
class LinkNode
{
	var data: Int;
	var next: LinkNode? ;
	init(_ data: Int)
	{
		// Set node value
		self.data = data;
		self.next = nil;
	}
}
class SingleLL
{
	var head: LinkNode? ;
	var tail: LinkNode? ;
	init()
	{
		self.head = nil;
		self.tail = nil;
	}
	// Insert node at last of linked list
	func insert(_ value: Int)
	{
		// Create a node
		let node: LinkNode? = LinkNode(value);
		if (self.head == nil)
		{
			// When linked list empty 
			// Add first node
			self.head = node;
		}
		else
		{
			// Add new node at end of linked list
			self.tail!.next = node;
		}
		self.tail = node;
	}
	// Display linked list nodes
	func display()
	{
		if (self.head  != nil)
		{
			print(" Linked List :", terminator: "");
			var temp: LinkNode? = self.head;
			while (temp  != nil)
			{
				// Display node data
				print("",temp!.data, terminator: " ");
				// Visit to next node
				temp = temp!.next;
			}
		}
		else
		{
			print("Empty Linked List");
		}
	}
	func findBalancedNode()
	{
		// Define Useful resultant variables
		var temp: LinkNode? = self.head;
		var result: LinkNode? = nil;
		// Define Useful calculations variables
		var totalSum: Int = 0;
		var currentSum: Int = 0;
		// Sum of all nodes
		while (temp  != nil)
		{
			// sum of node value
			totalSum += temp!.data;
			// Visit to next node
			temp = temp!.next;
		}
		// Get first node of linked list
		temp = self.head;
		while (temp  != nil && result == nil)
		{
			if (totalSum - (currentSum + temp!.data) == currentSum)
			{
				// When current node is balanced node
				result = temp;
			}
			// Calculate node sum 
			currentSum += temp!.data;
			// Visit to next node
			temp = temp!.next;
		}
		if (result  != nil)
		{
			print("\n Balanced node is : ",result!.data);
		}
		else
		{
			print("\n Balanced node not exist");
		}
	}
	static func main()
	{
		let sll1: SingleLL = SingleLL();
		let sll2: SingleLL = SingleLL();
		let sll3: SingleLL = SingleLL();
		// Create first linked list
		sll1.insert(1);
		sll1.insert(2);
		sll1.insert(3);
		sll1.insert(4);
		sll1.insert(2);
		sll1.insert(1);
		sll1.insert(3);
		// Second linked list
		sll2.insert(1);
		sll2.insert(3);
		sll2.insert(6);
		sll2.insert(1);
		sll2.insert(1);
		sll2.insert(1);
		sll2.insert(1);
		// Third linked list
		sll3.insert(1);
		sll3.insert(2);
		sll3.insert(3);
		// Display node elements
		sll1.display();
		// Find balanced node
		sll1.findBalancedNode();
		// Display node elements
		sll2.display();
		// Find balanced node
		sll2.findBalancedNode();
		// Display node elements
		sll3.display();
		// Find balanced node
		sll3.findBalancedNode();
	}
}
SingleLL.main();

Output

 Linked List : 1  2  3  4  2  1  3
 Balanced node is :  4
 Linked List : 1  3  6  1  1  1  1
 Balanced node is :  6
 Linked List : 1  2  3
 Balanced node not exist