bot_trust.rb

require 'fiber'

class Bot
  def initialize(color)
    @position = 1
    @color = color
    @fiber = Fiber.new do |buttons|
      while next_button = buttons.find{ |c,p| c == @color }
        if buttons.first == [@color,@position] && !$pushed
          push_button(@position)
          remaining_buttons = buttons.drop(1)
          $pushed = true
          break if remaining_buttons.empty?
          buttons = Fiber.yield(remaining_buttons)
        else 
          next_position = next_button[1]
          move_to_button(next_position)
          buttons = Fiber.yield(buttons)
        end
      end
      buttons
    end
  end
  
  def resume(buttons)
    @fiber.resume(buttons)
  end
  
  def push_button(number)
    #puts "#{@color}@#{@position} - Push button #{number}"
  end
  
  def move_to_button(target)
    old_postion = @position
    message = (target <=> @position) == 0 ? "Stay at" : "Move to"
    @position = @position + (target <=> @position)
    #puts "#{@color}@#{old_postion} - #{message} button #{@position}"
  end
  
  def alive?
    @fiber.alive?
  end
end

ARGF.readlines.drop(1).each_with_index do |line,index|
  buttons = line[2..-1].scan(/(\w) (\d+)/).map{ |color,position| [color,position.to_i]}
  #puts "buttons: #{buttons}"
  orange  = Bot.new('O')
  blue    = Bot.new('B')

  bots = [orange,blue]
  time = 0
  while bots.any?(&:alive?)
    $pushed = false
    time = time + 1

    buttons = bots.select(&:alive?).inject(buttons) do |buttons,bot|
      bot.resume(buttons)
    end
  end
  puts("Case #%d: %d" % [index+1, time] )
end