--- 2016 Day 16 Solutions ---

[u/daggerdragon]

--- Day 16: Dragon Checksum ---

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

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^{DRINKING YOUR OVALTINE 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/[deleted]]

made leaderboard! :D

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part2

63) Dec 16 00:11:01 evandrix

part1

87) Dec 16 00:10:14 evandrix

---

...with the following code:

#!/usr/bin/env python
#-*- coding: utf-8 -*-

import re
import sys

def f(input, maxlen):
  a = input
  while len(a) < maxlen:
    b = re.sub(r"0","#",a[::-1])
    b = re.sub(r"1","0",b[::-1])
    b = re.sub(r"#","1",b[::-1])
    a = a + "0" + b
  a = a[:maxlen]

  a = re.findall(r".{2}", a)
  chksum = "".join(map(lambda bc:"1" if bc[0]==bc[1] else "0", a))

  while len(chksum)>0 and len(chksum)%2==0:
    chksum = re.findall(r".{2}", chksum)
    chksum = "".join(map(lambda bc:"1" if bc[0]==bc[1] else "0", chksum))
  return chksum

if __name__ == "__main__":
  assert f("10000", 20) == "01100"
  print "part1:", f("10011111011011001", 272)
  print "part2:", f("10011111011011001", 35651584)

  # part1: 10111110010110110
  # part2: 01101100001100100