Reindeer Races from Advent of Code

reindeer.rb

# --- Day 14: Reindeer Olympics ---
#
# This year is the Reindeer Olympics! Reindeer can fly at high speeds, but must rest occasionally to recover their energy. Santa would like to know which of his reindeer is fastest, and so he has them race.
#
# Reindeer can only either be flying (always at their top speed) or resting (not moving at all), and always spend whole seconds in either state.

class Reindeer
  attr_accessor :name, :distance, :fly_time, :rest_time, :track, :points

  def initialize(name, distance, fly_time, rest_time)
    @name = name
    @distance = distance.to_i
    @fly_time = fly_time.to_i
    @rest_time = rest_time.to_i
    @track = Track.new(self)
    @points = 0
  end
end

class Track
  attr_accessor :reindeer, :kilometers

  def initialize(reindeer)
    @reindeer = reindeer
    # [@reindeer, "x", "x", "x", "x", "x", etc...]
    @kilometers = ("x" * 5000).split("")
    @flying = true
    @resting = false
    @time_elapsed_in_state = 0
    start_reindeer
  end

  def start_reindeer
    @kilometers[0] = reindeer
  end

  def advance_reindeer
    # one second at a time
    if @flying
      old_position = @kilometers.index(@reindeer)
      @kilometers[old_position + @reindeer.distance] = @reindeer
      @kilometers[old_position] = "x"
      @time_elapsed_in_state += 1
      if @time_elapsed_in_state == @reindeer.fly_time
        @flying = false
        @resting = true
        @time_elapsed_in_state = 0
      end
    elsif @resting
      @time_elapsed_in_state += 1
      if @time_elapsed_in_state == @reindeer.rest_time
        @flying = true
        @resting = false
        @time_elapsed_in_state = 0
      end
    end
  end

  def find_reindeer_index
    @kilometers.index(@reindeer)
  end
end

class Race
  def initialize(time, input)
    @time = time
    @racers = []
    @lead = nil
    register_racers(input)
  end

  def register_racers(input)
    # input comes in as follows:
    # Rudolph can fly 22 km/s for 8 seconds, but then must rest for 165 seconds.
    # Cupid can fly 8 km/s for 17 seconds, but then must rest for 114 seconds.
    input = input.map{|line| line.split(" can fly ")}
    input = input.map{|line| [line[0], line[-1].split(/\D/)]}.flatten
    input.delete("")
    while input.length > 0 do
      reindeer = Reindeer.new(input.shift, input.shift, input.shift, input.shift)
      @racers << reindeer
    end
  end

  def find_lead
    reindeer_positions = {}
    @racers.each do |reindeer|
      reindeer_positions[reindeer] = reindeer.track.find_reindeer_index
    end
    @lead = reindeer_positions.map{ |k, v| k if v == reindeer_positions.values.max }.compact
  end

  def run_race
    @time.times do
      @racers.each do |reindeer|
        reindeer.track.advance_reindeer
      end
    end
    @racers.map { |reindeer| reindeer.track.find_reindeer_index }.sort[-1]
  end

  # Seeing how reindeer move in bursts, Santa decides he's not pleased with the old scoring system.
  # Instead, at the end of each second, he awards one point to the reindeer currently in the lead. (If there are multiple reindeer tied for the lead, they each get one point.) He keeps the traditional 2503 second time limit, of course, as doing otherwise would be entirely ridiculous.

  def run_race_with_points
    @time.times do
      @racers.each { |reindeer| reindeer.track.advance_reindeer }
      find_lead
      @lead.each { |reindeer| reindeer.points += 1 }
    end
    @racers.map { |reindeer| reindeer.points }.sort[-1]
  end
end