Advent of Code 2023 - Day 4

solve.cr

require "string_scanner"

# Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53

puts "Let's gooooo!"

lines = [] of String # ooh fancy, types!
part_one_score = 0
part_two_card_count = 0

h = Hash(Int32, Int32).new(0)

STDIN.each_line do |line|
  card = line.split(":")
  num = card[0].gsub(/\D/, "").to_i
  game_data = card[1].split("|")
  winning_nums_set = game_data[0].scan(/\d+/).map() { |n| n[0].to_i }.to_set
  my_nums = game_data[1].scan(/\d+/).map() { |n| n[0].to_i }

  # Find the winning numbers by looping over my_nums and collecting those that are in the winning_nums_set
  winning_nums = my_nums.select() { |n| winning_nums_set.includes?(n) }

  card_count = 1 + h[num]
  part_two_card_count += card_count

  next if winning_nums.size == 0

  card_count.times() do
    # Push the winning card counts ahead
    winning_nums.each_with_index() do |n, i|
      next_card_num = num + 1 + i
      h[next_card_num] += 1
    end
  end

  # winning_num count must be > 0 so we can subtract one and raise 2 to that power
  score = 2 ** (winning_nums.size - 1)
  part_one_score += score
  
  puts "#{num} (x#{card_count}) #{winning_nums_set.join(",")} ||| #{my_nums.join(":")} => #{winning_nums.join(",")} => #{score}"
end

puts "Part 1 score: #{part_one_score}"
puts "Part 2 total card count: #{part_two_card_count}"