Advent of Code, day 3

day3.rb

#!/usr/bin/env ruby

# http://adventofcode.com/day/3

require "set"

class Visits

  def initialize
    @locations = Set.new
  end

  def traverse(path)
    coord = [0, 0]
    @locations << coord
    path.each do |c|
      delta = DIRS.fetch(c)
      coord = coord.zip(delta).map { |a, d| a + d }
      @locations << coord
    end
  end

  def count
    @locations.count
  end

  private

  DIRS = {
    "^" => [0, -1],
    "v" => [0, +1],
    "<" => [-1, 0],
    ">" => [+1, 0],
  }
   
end

PATH = File.read("input").chars

# part 1
visits = Visits.new  
visits.traverse(PATH)
puts visits.count

# part 2
visits = Visits.new
PATH.partition.with_index do |c, i|
  i.even?
end.each do |individual_path|
  visits.traverse(individual_path)
end
puts visits.count