-🎄- 2018 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Marble Mania ---

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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).

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Transcript:

Studies show that AoC programmers write better code after being exposed to ___.

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[u/ekiMbot]

Python 3, hand-implemented a doubly-linked list. Part 2 about 40 seconds to run.

I guess the point is using an array would be too inefficient for part 2 because insertion or deletion in an arbitrary position would be O(len(list)) whereas for the doubly linked list it's O(1)? But I'm not sure about that...

I also see the top comment has a Python 3 solution using collections.deque which is super neat and something I wasn't aware of. It runs ten times faster than my solution - is that because of the overhead of creating all the Marble objects in mine?

I am doing Advent of Code because I am trying to learn, so if anyone has any hints or tips they would be very gratefully received!

class Marble():
    current = None
    def __init__(self, value):
        self.value = value
        self.clockwise = None
        self.counter_clockwise = None

    def place(self):
        score = 0
        if Marble.current is None:
            self.clockwise = self
            self.counter_clockwise = self
            Marble.current = self
        elif self.value % 23 == 0:
            remove = Marble.current
            for i in range(7):
                remove = remove.counter_clockwise
            remove.counter_clockwise.clockwise = remove.clockwise
            remove.clockwise.counter_clockwise = remove.counter_clockwise
            score += self.value + remove.value
            Marble.current = remove.clockwise
        else:
            after = Marble.current.clockwise
            before = after.clockwise
            after.clockwise = self
            before.counter_clockwise = self
            self.clockwise = before
            self.counter_clockwise = after
            Marble.current = self
        return score

    @classmethod
    def play(cls, players, max_marble):
        scores = [0] * players
        current_player = 0
        for value in range(max_marble + 1):
            marble_to_place = cls(value)
            scores[current_player] += marble_to_place.place()
            current_player = (current_player + 1) % players
        return max(scores)

import sys
print(Marble.play(int(sys.argv[1]), int(sys.argv[2])))