Advent of Code 2024 day007.rb

day007.rb

require_relative "main"

module Day007
  INPUT = File.read('INPUT.txt')

  DATA = INPUT.split("\n").map do |line|
    parts = line.split(":")
    [
      parts[0].to_i,
      parts[1].split(" ").map(&:to_i)
    ]
  end

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

  dfs1 = ->(n, l) do
    return n == l[0] * l[-1] || n == l[0] + l[-1] if l.count == 2
    n % l[-1] == 0 && dfs1.call(n / l[-1], l[0...-1]) || \
      n >= l[-1] && dfs1.call(n - l[-1], l[0...-1])
  end

  answer1 = DATA.sum { dfs1.call(_1[0], _1[1]) ? _1[0] : 0 }

  pp answer1

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

  dfs2 = ->(n, l) do
    return n == l[0] * l[-1] || n == l[0] + l[-1] || n.to_s == l[0].to_s + l[-1].to_s if l.count == 2
    n % l[-1] == 0 && dfs2.call(n / l[-1], l[0...-1]) || \
      n >= l[-1] && dfs2.call(n - l[-1], l[0...-1]) || \
      n.to_s.end_with?(l[-1].to_s) && dfs2.call(n.to_s[0...-l[-1].to_s.length].to_i, l[0...-1])
  end

  answer2 = DATA.sum { dfs2.call(_1[0], _1[1]) ? _1[0] : 0 }

  pp answer2
end