94 lines
2.5 KiB
Python
94 lines
2.5 KiB
Python
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#!/usr/bin/env python
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import dataclasses
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import sys
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from collections import Counter, deque
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from typing import Literal, Optional
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@dataclasses.dataclass
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class Operation:
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lhs: Optional[int]
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operator: Literal["+", "*"]
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rhs: Optional[int]
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def __call__(self, old: int) -> int:
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lhs = old if self.lhs is None else self.lhs
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rhs = old if self.rhs is None else self.rhs
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if self.operator == "*":
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return lhs * rhs
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if self.operator == "+":
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return lhs + rhs
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assert False
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@classmethod
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def from_input(cls, input: str) -> "Operation":
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assert input.startswith(" Operation: new = ")
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lhs, op, rhs = input.split()[-3:]
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assert op in ("+", "*") # Sanity check
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return cls(
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None if lhs == "old" else int(lhs),
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op, # type: ignore
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None if rhs == "old" else int(rhs),
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)
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@dataclasses.dataclass
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class Monkey:
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items: deque[int]
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operation: Operation
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test_divisor: int
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transfer: dict[bool, int]
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@classmethod
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def from_input(cls, input: list[str]) -> "Monkey":
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# Sanity checks
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assert input[0].startswith("Monkey ")
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assert "divisible by" in input[3]
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assert "true" in input[4]
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assert "false" in input[5]
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items = deque(
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int(n) for n in input[1].removeprefix(" Starting items: ").split(",")
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)
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operation = Operation.from_input(input[2])
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divisor = int(input[3].split()[-1])
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transfer = {
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True: int(input[4].split()[-1]),
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False: int(input[5].split()[-1]),
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}
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return Monkey(items, operation, divisor, transfer)
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def solve(input: list[str]) -> int:
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def do_round(monkeys: list[Monkey], counts: dict[int, int]) -> None:
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for i, monkey in enumerate(monkeys):
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counts[i] += len(monkey.items)
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while monkey.items:
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item = monkey.items.popleft()
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item = monkey.operation(item)
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item //= 3
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target = monkey.transfer[(item % monkey.test_divisor) == 0]
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monkeys[target].items.append(item)
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monkeys = [Monkey.from_input(monkey_spec.splitlines()) for monkey_spec in input]
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counts: Counter[int] = Counter()
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for _ in range(20):
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do_round(monkeys, counts)
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((_, a), (_, b)) = counts.most_common(2)
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return a * b
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def main() -> None:
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input = sys.stdin.read().split("\n\n")
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print(solve(input))
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if __name__ == "__main__":
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main()
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