class LinkedListNode

	attr_accessor :value, :next_node

	def initialize(value, next_node=nil)
		@value = value
		@next_node = next_node
	end
end

def print_values(list_node)

	if list_node
		print "#{list_node.value} --> "
		print_values(list_node.next_node)
	else
		print "nil\n"
		return
	end
end

class Stack
	attr_reader :data

	def initialize
		@data = nil
	end

	def push(value)
		@data << (value)
	end

	def pop
		value = @data.value
		@data = @data.next_node
		value
	end
end

def reverse_list(list, previous=nil)

  current_head = list.next_node
  list.next_node = previous

  if current_head
    reverse_list(current_head, list)
  else
    list
  end
end

node1 = LinkedListNode.new(37)
node2 = LinkedListNode.new(99, node1)
node3 = LinkedListNode.new(12, node2)

print_values(node3)

puts "-------"

revlist = reverse_list(node3)

print_values(revlist)