aoc_2023_5_two.rb

# frozen_string_literal: true
require 'parallel'

FILE = 'input.txt'
# FILE = 'sample.txt'
raw_input = File.read(FILE)
lines = raw_input.split("\n")

seed_num_pairs = []
seed_nums = []
location_nums = []
conversion = {} 

puts "Generating seed nums..."
seed_num_line = lines[0].split(':')[1].split(' ').map(&:to_i)
seed_num_line.each_slice(2) do |slice|
  seed_num_pairs << slice
end

pp seed_num_pairs

def get_location_num(key, num, conversion)
  return num if key == 'location'

  source = key
  dest = conversion[key]['dest']
  mapped_num = num

  # Check if num is in source's source nums
  source_map_has_num = false
  conversion[key]['mappings'].each do |nums|
    source_map_has_num ||= Range.new(nums[1], nums[1]+nums[2]-1).cover?(num)
    if source_map_has_num
      # get mapped num
      diff = num-nums[1]
      mapped_num = nums[0]+diff
      break
    end
  end

  get_location_num(dest, mapped_num, conversion)
end

puts "Generating conversion mappings..."
i = 2
while lines[i]
  if lines[i].include?('map')
    keys = lines[i].split(' ')[0].split('-to-')
    source = keys[0]
    dest = keys[1]

    i += 1
    while lines[i] && lines[i] != ''
      conversion[source] = { 'mappings' => [] } unless conversion.key?(source)
      conversion[source]['dest'] = dest
      conversion[source]['mappings'] << lines[i].split(' ').map(&:to_i)

      i += 1
    end
  end

  i += 1
end

puts "Calculating minimum location..."
min_location = Parallel.map_with_index(seed_num_pairs, in_threads: 4) do |pair, index|
  min_location = get_location_num('seed', pair[0], conversion)

  j = 1
  while j < pair[1]
    min_location = [min_location, get_location_num('seed', pair[0]+j, conversion)].min
    j += 1

    puts "Pair #{index+1}; Progress: #{100*j/pair[1]}%" if j % 200_000 == 0
  end

  min_location
end.min

puts min_location