97 lines
2.5 KiB
Python
97 lines
2.5 KiB
Python
import itertools
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from collections import defaultdict
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from typing import Any, Iterator
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from ..base import BaseSolver
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Directions = list[
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tuple[
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str, tuple[int, int], tuple[tuple[int, int], tuple[int, int], tuple[int, int]]
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]
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]
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# (Y, X)
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DIRECTIONS: Directions = [
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("N", (-1, 0), ((-1, -1), (-1, 0), (-1, 1))),
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("S", (1, 0), ((1, -1), (1, 0), (1, 1))),
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("W", (0, -1), ((-1, -1), (0, -1), (1, -1))),
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("E", (0, 1), ((-1, 1), (0, 1), (1, 1))),
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]
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def min_max_yx(positions: set[tuple[int, int]]) -> tuple[int, int, int, int]:
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ys, xs = {y for y, _x in positions}, {x for _y, x in positions}
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return min(ys), min(xs), max(ys), max(xs)
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def round(
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positions: set[tuple[int, int]],
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directions: Directions,
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):
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to_move: dict[tuple[int, int], list[tuple[int, int]]] = defaultdict(lambda: [])
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for y, x in positions:
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elves = {
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(dy, dx): (y + dy, x + dx) in positions
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for dy, dx in itertools.product((-1, 0, 1), (-1, 0, 1))
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if (dy, dx) != (0, 0)
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}
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if not any(elves.values()):
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to_move[y, x].append((y, x))
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continue
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found: str | None = None
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for d, (dy, dx), d_yx_check in directions:
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if not any(elves[dy, dx] for dy, dx in d_yx_check):
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found = d
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to_move[y + dy, x + dx].append((y, x))
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break
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if found is None:
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to_move[y, x].append((y, x))
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positions.clear()
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for ty, tx in to_move:
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if len(to_move[ty, tx]) > 1:
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positions.update(to_move[ty, tx])
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else:
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positions.add((ty, tx))
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directions.append(directions.pop(0))
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class Solver(BaseSolver):
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def solve(self, input: str) -> Iterator[Any]:
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POSITIONS = {
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(i, j)
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for i, row in enumerate(input.splitlines())
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for j, col in enumerate(row)
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if col == "#"
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}
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# === part 1 ===
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p1, d1 = POSITIONS.copy(), DIRECTIONS.copy()
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for _ in range(10):
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round(p1, d1)
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min_y, min_x, max_y, max_x = min_max_yx(p1)
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yield sum(
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(y, x) not in p1
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for y in range(min_y, max_y + 1)
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for x in range(min_x, max_x + 1)
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)
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# === part 2 ===
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p2, d2 = POSITIONS.copy(), DIRECTIONS.copy()
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answer_2 = 0
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while True:
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answer_2 += 1
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backup = p2.copy()
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round(p2, d2)
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if backup == p2:
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break
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yield answer_2
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