Advent of Code 2023 day004.rb

day004.rb

require_relative "main"

module Day004
  INPUT = File.read('INPUT.txt')

  lines = INPUT.to_lines
  result_counts = lines.map do |line|
    data = line.split_strip(":").last
    winning, mine = data.split_strip("|").map { _1.split_strip(" ").map(&:to_i) }

    (mine & winning).count
  end

  ##########
  # Part 1 #
  ##########

  answer1 = result_counts.reduce(0) do |memo, count|
    memo + ((count > 0) ? 2**(count - 1) : 0)
  end

  pp answer1

  ##########
  # Part 2 #
  ##########

  counts = Array.new(result_counts.count, 1)
  result_counts.each.with_index do |result_count, i|
    counts[i].times do
      result_count.times { |j| counts[1 + i + j] += 1 }
    end
  end

  answer2 = counts.sum

  pp answer2
end