d5_part_one.rb

# frozen_string_literal: true

def day5_part_one(input)
  almanac = {}
  # Parse the input
  seeds =
    input[0]
      .scan(/seeds: (.*)/)
      .flatten[0]
      .split(" ")
      .map(&:to_i)

  map_type = ""
  input[1..]
    .each do |line|
      next if line.empty?

      if line.include?("map:")
        map_type = line.gsub(" map:", "")
        next
      end

      numbers = line.split(" ").map(&:to_i)
      almanac[map_type] ||= []
      almanac[map_type] << { dest: numbers[0], source: numbers[1], range: numbers[2] }
    end

  seeds.reduce(0) do |min_location, seed|
    # Reduce each seed to its location
    location =
      almanac.reduce(seed) do |source, (_, maps)|
        valid_maps = maps.reject do |m|
          m[:source] > source || (m[:source] + m[:range]) < source
        end

        next source if valid_maps.empty?

        entry =
          valid_maps.find do |m|
            (m[:source]...(m[:source] + m[:range])).include?(source)
          end

        next source unless entry # same destination as it is not mapped

        entry[:dest] + (1..(source - entry[:source])).size
      end

    min_location.zero? ? location : [min_location, location].min
  end
end

test = <<~INPUT
  seeds: 79 14 55 13

  seed-to-soil map:
  50 98 2
  52 50 48

  soil-to-fertilizer map:
  0 15 37
  37 52 2
  39 0 15

  fertilizer-to-water map:
  49 53 8
  0 11 42
  42 0 7
  57 7 4

  water-to-light map:
  88 18 7
  18 25 70

  light-to-temperature map:
  45 77 23
  81 45 19
  68 64 13

  temperature-to-humidity map:
  0 69 1
  1 0 69

  humidity-to-location map:
  60 56 37
  56 93 4
INPUT
  .split(/\n/)

puts day5_part_one(test)

# Large puzzle input
file = File.open("d5.txt")
file_data = file.readlines.map(&:chomp)
file.close

puts day5_part_one(file_data)