cycle_detector.rb

cycledetector.rb

class CycleDetector

  def initialize(list)
    @tortoise = list
    @hare = list.next_node if list
  end

  def self.detect(list)
    self.new(list).detect
  end

  def detect
    while list_continues?
      move_tortoise
      move_hare
      return true if @tortoise == @hare
    end
    return false
  end

  private

  def move_hare
    if @hare.next_node
      @hare = @hare.next_node.next_node 
    else
      @hare = nil
    end
  end

  def move_tortoise
    @tortoise = @tortoise.next_node
  end

  def list_continues?
    @tortoise && @hare
  end

end