Flatten a folded linked list in ruby

Ruby program for Flatten a folded linked list. Here problem description and other solutions.

#  Ruby program for
#  Unfold a folded linked list OR
#  flatten folded linked list

#  Linked list node
class LinkNode 
	# Define the accessor and reader of class LinkNode
	attr_reader :data, :next
	attr_accessor :data, :next
	def initialize(data) 
		self.data = data
		self.next = nil
	end
end

class SingleLL 
	# Define the accessor and reader of class SingleLL
	attr_reader :head
	attr_accessor :head
	def initialize() 
		self.head = nil
	end

	#  Insert node at the beginning of linked list
	def addNode(data) 
		#  Create node
		node = LinkNode.new(data)
		node.next = self.head
		#  Set new head
		self.head = node
	end

	#  Display linked list element
	def display() 
		if (self.head == nil) 
			return
		end

		temp = self.head
		#  iterating linked list elements
		while (temp != nil) 
			print(" ", temp.data ," →")
			#  Visit to next node
			temp = temp.next
		end

		print(" NULL\n")
	end

	#  This is handle the request of unfold given linked list nodes
	def unfoldList() 
		if (self.head == nil) 
			print("\n Empty linked list\n")
			return
		end

		temp = self.head
		auxiliary = nil
		hold = nil
		#  Loop which is separating the fold elements 
		while (temp.next != nil) 
			#  Get the second element
			hold = temp.next
			if (hold.next != nil) 
				#  When exists pair of three elements
				temp.next = hold.next
				#  Visit to 3rd element
				temp = hold.next
			else
				#  When get last two elements
				temp.next = nil
			end

			#  Add new node at beginning of auxiliary linked list
			hold.next = auxiliary
			#  Make new head node
			auxiliary = hold
		end

		if (temp != nil) 
			#  Combine lists
			temp.next = auxiliary
		end
	end
end

def main() 
	#  Create a empty linked lists
	sll1 = SingleLL.new()
	sll2 = SingleLL.new()
	#   Constructed first linked list
	#   2 → 5 → 1 → 8 → 10 → 4 → 9 → 7 → NULL
	sll1.addNode(7)
	sll1.addNode(9)
	sll1.addNode(4)
	sll1.addNode(10)
	sll1.addNode(8)
	sll1.addNode(1)
	sll1.addNode(5)
	sll1.addNode(2)
	#  Constructed second linked list
	#  1 → 2 → 3 → 4 → 5 → 6 → 7 → NULL
	sll2.addNode(7)
	sll2.addNode(6)
	sll2.addNode(5)
	sll2.addNode(4)
	sll2.addNode(3)
	sll2.addNode(2)
	sll2.addNode(1)
	#  Test A
	print(" Before unfold\n")
	sll1.display()
	sll1.unfoldList()
	print(" After unfold\n")
	sll1.display()
	#  Test B
	print(" Before unfold\n")
	sll2.display()
	sll2.unfoldList()
	print(" After unfold\n")
	sll2.display()
end

main()

Output

 Before unfold
 2 → 5 → 1 → 8 → 10 → 4 → 9 → 7 → NULL
 After unfold
 2 → 1 → 10 → 9 → 7 → 4 → 8 → 5 → NULL
 Before unfold
 1 → 2 → 3 → 4 → 5 → 6 → 7 → NULL
 After unfold
 1 → 3 → 5 → 7 → 6 → 4 → 2 → NULL