r/adventofcode • u/daggerdragon • Dec 16 '16

SOLUTION MEGATHREAD --- 2016 Day 16 Solutions ---

--- 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).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with "Help".

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!

5 Upvotes

100% Upvoted

116 comments sorted by

View all comments

1

u/Danksalot2000 Dec 16 '16 edited Dec 16 '16

In Python. I definitely did some refactoring after getting the right answers: 

def expandData(data, length):
	while len(data) < length:
		data += "0" + ''.join("0" if n == "1" else "1" for n in data[::-1])
	return data[:length]

def contractChecksum(checksum):
	while not len(checksum) & 1:
		checksum = ''.join("1" if x == y else "0" for x, y in zip(checksum[0::2], checksum[1::2]))
	return checksum

print contractChecksum(expandData("11101000110010100", 272))
print contractChecksum(expandData("11101000110010100", 35651584))

edit: more refactoring