version2.rb

class LinkedListNode
  attr_accessor :value, :next_node
 
  def initialize(value, next_node=nil)
    @value = value
    @next_node = next_node
  end
end
 
class Stack
  attr_reader :data
  
  def initialize
    @data = nil
  end
 
  # Push a value onto the stack
  def push(value)
    @data = LinkedListNode.new(value, @data)
  end
 
  # Pop an item off the stack.  
  # Remove the last item that was pushed onto the
  # stack and return the value to the user
  def pop
    last_stacked_item = @data.value
 
    if @data.next_node.nil?
      @data = nil
    else
      @data = @data.next_node
    end
 
    last_stacked_item
  end
end
 
def reverse_list(list)
  while list
    rev = LinkedList.new(list.value, rev)
  end
 
  rev
end
 
def print_values(list_node)
  print "#{list_node.value} --> "
  if list_node.next_node.nil?
    print "nil\n"
    return
  else
    print_values(list_node.next_node)
  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)