125 lines
2.7 KiB
Python
125 lines
2.7 KiB
Python
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import fileinput
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import itertools
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from pprint import pprint
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from collections import deque
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from typing import List, Deque, Dict, Tuple, Optional, Set
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from copy import deepcopy
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Deck = Deque[int]
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Decks = Dict[int, Deck]
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FrozenDeck = Tuple[Tuple[int, ...], Tuple[int, ...]]
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def parse() -> Decks:
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decks: Decks = {}
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deck: Optional[Deck] = None
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player: Optional[int] = None
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for line in fileinput.input():
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line = line.strip()
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if line.startswith("Player "):
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if deck and player:
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decks[player] = deck
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deck = deque()
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player = int(line[len("Player ") : -1])
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elif line.isdigit():
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assert deck is not None
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deck.append(int(line))
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if deck and player:
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decks[player] = deck
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return decks
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def part1_round(decks: Decks):
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p1 = decks[1].popleft()
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p2 = decks[2].popleft()
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assert p1 != p2
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if p1 > p2:
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decks[1].extend((p1, p2))
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else:
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decks[2].extend((p2, p1))
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def part1(decks: Decks) -> None:
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i = 0
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while decks[1] and decks[2]:
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part1_round(decks)
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i += 1
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winner = 1 if decks[1] else 2
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score = sum(card * (i + 1) for i, card in enumerate(reversed(decks[winner])))
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print("Part 1:", score, "(player", winner, "won)")
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def freeze_decks(decks: Decks) -> FrozenDeck:
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return (
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tuple(decks[1]),
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tuple(decks[2]),
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)
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def part2_round(decks: Decks, history: Set[FrozenDeck]):
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frozen = freeze_decks(decks)
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if frozen in history:
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# Player 1 wins if the round happened before
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return 1
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if not decks[1]:
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return 2
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if not decks[2]:
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return 1
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history.add(frozen)
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p1 = decks[1].popleft()
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p2 = decks[2].popleft()
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assert(p1 != p2)
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if len(decks[1]) >= p1 and len(decks[2]) >= p2:
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new_decks = {
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1: deque(list(decks[1])[:p1]),
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2: deque(list(decks[2])[:p2]),
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}
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winner = part2_game(new_decks)
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elif p1 > p2:
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winner = 1
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else:
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winner = 2
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assert(winner == 1 or winner == 2)
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if winner == 1:
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decks[1].extend((p1, p2))
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elif winner == 2:
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decks[2].extend((p2, p1))
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def part2_game(decks: Decks) -> Optional[int]:
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i = 0
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history: Set[FrozenDeck] = set()
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winner: Optional[int] = None
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while winner is None:
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winner = part2_round(decks, history)
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i += 1
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return winner
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def part2(decks: Decks) -> None:
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winner = part2_game(decks)
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assert(winner is not None)
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score = sum(card * (i + 1) for i, card in enumerate(reversed(decks[winner])))
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print("Part 2:", score, "(player", winner, "won)")
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def main() -> None:
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decks = parse()
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part1(deepcopy(decks))
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part2(decks)
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if __name__ == "__main__":
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main()
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