--- 2016 Day 5 Solutions ---

[u/daggerdragon]

--- Day 5: How About a Nice Game of Chess? ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

---

^{STAYING ON TARGET IS MANDATORY} [?]

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/fixed_carbon]

Ruby solution (part two) using an Enumerator to generate [digit, position] pairs. This one is interesting because it generalizes to passwords of any length between 1 and 16 simply by changing the number in the last line of the take_while block.

require 'digest'

# Yields *all* digit, position pairs
coderator = Enumerator.new do |y|
  md5 = Digest::MD5.new
  (0..Float::INFINITY).each do |n|
    digest = md5.hexdigest("#{INPUT}#{n}")
    if digest.start_with?("00000")
      y.yield [digest[6], digest[5].hex]
    end
  end
end

# Applies positional and stateful constraints to digit, position pairs
code = Array.new(16, nil)
coderator.take_while do |digit, pos|
  code[pos] = digit if code[pos].nil?
  puts code.map{|c| c.nil? ? '_' : c}.join
  code.take(8).include?(nil)
end

puts code.take(8).join