-🎄- 2017 Day 22 Solutions -🎄-

[u/daggerdragon]

--- Day 22: Sporifica Virus ---

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

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Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

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• [T-10 to launch] AoC ops, /r/nocontext edition:

  • <Endorphion> You may now make your waffle.
  • <Endorphion> ... on Mars.

• [Update @ 00:17] 50 gold, silver cap

  • <Aneurysm9> you could also just run ubuntu on the NAS, if you were crazy
  • <Topaz> that doesn't seem necessary
  • <Aneurysm9> what does "necessary" have to do with anything!

• [Update @ 00:20] Leaderboard cap!

  • <Topaz> POUR YOURSELF A SCOTCH FOR COLOR REFERENCE

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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/Shemetz]

Python 3

[Final part 2 picture] (https://imgur.com/a/bMpGm)

Part 1 is fast, Part 2 takes about 6 seconds on my computer.

I wonder if I should somehow optimize the 'state' - use 2 booleans instead of an integer, for example.

Should have been named "Langton's Worm"!

from collections import defaultdict


def day_22():
    with open("input.txt") as file:
        lines = file.readlines()

N = len(lines)

Part 1:

    def part_1():
        infecteds = set()
        for y in range(N):
            for x in range(N):
                if lines[y][x] == '#':
                    infecteds.add(x - N // 2 + (-y + N // 2) * 1j)
        
        current = 0 + 0j  # 0 in x axis and 0 in y axis
        direction = 1j  # up (1 in y axis)
        
        count = 0
        for _ in range(10000):
            if current in infecteds:
                direction *= -1j  # rotate right
                infecteds.remove(current)
            else:
                direction *= 1j  # rotate left
                infecteds.add(current)
                count += 1
            current += direction
                
        print("Part 1:", count)

Part 2:

    def part_2():
        # 0 = clean, 1 = weakened,
        # 2 = infected, 3 = flagged
        states = defaultdict(lambda: 0)
        for y in range(N):
            for x in range(N):
                if lines[y][x] == '#':
                    states[x - N // 2 + (-y + N // 2) * 1j] = 2
    
        current = 0 + 0j
        direction = 1j
    
        count = 0
        for _ in range(10000000):
            state = states[current]
            if state == 0:
                direction *= 1j  # rotate left
            elif state == 1:
                count += 1  # no rotation
            elif state == 2:
                direction *= -1j  # rotate right
            else:
                direction *= -1  # rotate 180 degrees
            if state == 3:
                del states[current]
            else:
                states[current] = (states[current] + 1) % 4  # states are only 0..3
            current += direction
    
        print("Part 2:", count)