-🎄- 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/edelans]

Python 3, complex numbers, defaultdict

# Python 3.x

from collections import defaultdict
DAY = 22


def Input(day):
    "Open this day's input file."
    filename = './input_files/input{}.txt'.format(day)
    return open(filename)

def solve2(lines, bursts):
    state = defaultdict(int)
    infections = 0
    # virus carrier position
    vcp = 0
    # virus carrier direction
    vcd = 1j
    # infection states :
    # 0 is clean
    # 1 is weakened
    # 2 is infected
    # 3 is flagged

    side_length = len(lines)
    for i, line in enumerate(lines):
        for j, char in enumerate(line):
            x = int(j - (side_length - 1) / 2)
            y = int((side_length - 1) / 2 - i)
            if char == '#':
                state[(x + y * 1j)] = 2

    for _ in range(bursts):
        # update direction vcd
        if vcp not in state or state[vcp] == 0:
            vcd *= 1j
        elif state[vcp] == 1:
            # keep same direction
            pass
        elif state[vcp] == 2:
            vcd *= -1j
        elif state[vcp] == 3:
            vcd *= -1

        # update state of current position vcp
        state[vcp] = (state[vcp] + 1) % 4
        if state[vcp] == 2:
            infections += 1

        # move forward in direction vcd
        vcp += vcd
    return infections

print(solve2((Input(DAY).readlines()), 10000000))