Insert linked list node at nth last position in ruby

Ruby program for Insert linked list node at nth last position. Here problem description and explanation.

#  Ruby program for
#  Insert linked list node at nth last position 

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

	#  insert node at end position
	def insert(value) 
		#  Create a new node
		node = LinkNode.new(value)
		if (self.head == nil) 
			self.head = node
		else
 
			temp = self.head
			#  Find the last node
			while (temp.next != nil) 
				#  Visit to next node
				temp = temp.next
			end

			#  Add node
			temp.next = node
		end

	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

	#  Add node at specific position from the end of linked list
	def endPosition(position, value) 
		if (self.head == nil) 
			print("Empty Linked list", "\n")
		elsif (position <= 0) 
			print("Invalid position", "\n")
		else
 
			temp = self.head
			location = nil
			while (temp != nil) 
				position -= 1
				if (position <= 0) 
					if (location == nil) 
						location = self.head
					else
 
						location = location.next
					end

				end

				#  visit to next node
				temp = temp.next
			end

			if (position <= 1) 
				node = LinkNode.new(value)
				if (location == nil) 
					#  Add node at first place
					node.next = self.head
					self.head = node
				else
 
					#  Add node at intermediate position
					node.next = location.next
					location.next = node
				end

			else
 
				print("Opps position not found", "\n")
			end

		end

	end

end

def main() 
	sll = LinkedList.new()
	#  Add node
	sll.insert(5)
	sll.insert(4)
	sll.insert(3)
	sll.insert(2)
	sll.insert(1)
	sll.display()
	position = 2
	data = 10
	sll.endPosition(position, data)
	print(" Add ", data ," at last ", 
          position ,"-nd position", "\n")
	sll.display()
end

main()

Output

5 → 4 → 3 → 2 → 1 → NULL
 Add 10 at last 2-nd position
5 → 4 → 3 → 2 → 10 → 1 → NULL