Find Nth from end of a linked list

nthFromEnd.rb

class Node
  attr_accessor :nextNode, :value
  def initialize(value, nextNode = nil)
    @value = value
    @nextNode = nextNode
  end
end

def nthFromEnd(startNode, n)
  rabbit = turtle = startNode

  # jump rabbit ahead of turtle n nodes
  while n >= 0 do
    n -= 1
    rabbit = rabbit.nextNode
  end

  # move rabbit and turtle ahead till rabbit reaches the end
  while not rabbit.nil? do
    rabbit = rabbit.nextNode
    turtle = turtle.nextNode
  end

  turtle.nextNode
end

# build 10 nodes
nodes = 10.times.collect { |i| Node.new i }

# link them together
nodes.each_with_index do |node, i|
  if i != 0
    nodes[i-1].nextNode = node
  end
end

# node values
# [0,1,2,3,4,5,6,7,8,9]
p nthFromEnd(nodes[0], 3).value # outputs 7