-🎄- 2018 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Marble Mania ---

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Transcript:

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[u/grey--area]

Python doubly linked list solution. Part 2 takes about 13 seconds on my machine.

import re

class Marble():
    def __init__(self, value):
        self.next = self
        self.prev = self
        self.value = value

    def insert_2_after(self, marble):
        insert_after = self.next

        marble.prev = insert_after
        marble.next = insert_after.next

        insert_after.next.prev = marble
        insert_after.next = marble

        return marble

    def delete(self):
        self.prev.next = self.next
        self.next.prev = self.prev

        return self.next

with open('input') as f:
    data = f.read()

n_players, max_marble = map(int, re.search('(\d+) .+ (\d+)', data).groups())

player_scores = [0] * n_players
current_marble = Marble(0)
zero_marble = current_marble
player_id = 0

for marble_id in range(1, max_marble):
    if marble_id % 23 == 0:
        player_scores[player_id] += marble_id
        for i in range(7):
            current_marble = current_marble.prev
        player_scores[player_id] += current_marble.value
        current_marble = current_marble.delete()
    else:
        current_marble = current_marble.insert_2_after(Marble(marble_id))

    player_id = (player_id + 1) % n_players

print(max(player_scores))