Advent of Code 2024 day008.rb

day008.rb

require_relative "main"

module Day008
  INPUT = File.read("INPUT.txt")

  EMPTY = "."

  grid = INPUT.to_grid

  h = grid.each_with_object(Hash.new { |h, k| h[k] = [] }) { |v, c, memo| memo[c].push(v) if c != EMPTY }

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

  ns = h.values.each_with_object([]) do |vs, memo|
    i = 0
    while i < vs.length
      j = i + 1
      while j < vs.length

        d = vs[j] - vs[i]
        a = vs[j] + d
        b = vs[i] - d

        memo.push(a) if grid.in_bounds?(a) && !memo.include?(a)
        memo.push(b) if grid.in_bounds?(b) && !memo.include?(b)

        j += 1
      end
      i += 1
    end
  end

  answer1 = ns.count

  pp answer1

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

  ns = h.values.each_with_object([]) do |vs, memo|
    i = 0
    while i < vs.length
      j = i + 1
      while j < vs.length

        d = vs[j] - vs[i]
        a = vs[j]
        b = vs[i]

        loop do
          memo.push(a) unless memo.include?(a)
          a += d
          break unless grid.in_bounds?(a)
        end

        loop do
          memo.push(b) unless memo.include?(b)
          b -= d
          break unless grid.in_bounds?(b)
        end

        j += 1
      end
      i += 1
    end
  end

  answer2 = ns.count

  pp answer2
end