111 lines
2.9 KiB
Python
111 lines
2.9 KiB
Python
import os
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import sys
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from typing import Literal, TypeAlias, cast
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VERBOSE = os.getenv("AOC_VERBOSE") == "True"
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CellType: TypeAlias = Literal[".", "|", "-", "\\", "/"]
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Direction: TypeAlias = Literal["R", "L", "U", "D"]
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Mappings: dict[
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CellType,
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dict[
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Direction,
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tuple[tuple[tuple[int, int, Direction], ...], tuple[Direction, ...]],
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],
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] = {
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".": {
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"R": (((0, +1, "R"),), ("R", "L")),
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"L": (((0, -1, "L"),), ("R", "L")),
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"U": (((-1, 0, "U"),), ("U", "D")),
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"D": (((+1, 0, "D"),), ("U", "D")),
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},
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"-": {
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"R": (((0, +1, "R"),), ("R", "L")),
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"L": (((0, -1, "L"),), ("R", "L")),
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"U": (((0, +1, "R"), (0, -1, "L")), ("U", "D")),
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"D": (((0, +1, "R"), (0, -1, "L")), ("U", "D")),
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},
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"|": {
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"U": (((-1, 0, "U"),), ("U", "D")),
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"D": (((+1, 0, "D"),), ("U", "D")),
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"R": (((-1, 0, "U"), (+1, 0, "D")), ("R", "L")),
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"L": (((-1, 0, "U"), (+1, 0, "D")), ("R", "L")),
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},
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"/": {
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"R": (((-1, 0, "U"),), ("R", "D")),
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"L": (((+1, 0, "D"),), ("L", "U")),
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"U": (((0, +1, "R"),), ("U", "L")),
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"D": (((0, -1, "L"),), ("R", "D")),
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},
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"\\": {
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"R": (((+1, 0, "D"),), ("R", "U")),
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"L": (((-1, 0, "U"),), ("L", "D")),
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"U": (((0, -1, "L"),), ("U", "R")),
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"D": (((0, +1, "R"),), ("L", "D")),
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},
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}
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def propagate(
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layout: list[list[CellType]], start: tuple[int, int], direction: Direction
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) -> list[list[tuple[Direction, ...]]]:
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n_rows, n_cols = len(layout), len(layout[0])
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beams: list[list[tuple[Direction, ...]]] = [
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[() for _ in range(len(layout[0]))] for _ in range(len(layout))
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]
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queue = [(start, direction)]
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while queue:
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(row, col), direction = queue.pop()
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if (
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row not in range(0, n_rows)
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or col not in range(0, n_cols)
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or direction in beams[row][col]
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):
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continue
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moves, update = Mappings[layout[row][col]][direction]
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beams[row][col] += update
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for move in moves:
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queue.append(((row + move[0], col + move[1]), move[2]))
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return beams
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layout: list[list[CellType]] = [
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[cast(CellType, col) for col in row] for row in sys.stdin.read().splitlines()
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]
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beams = propagate(layout, (0, 0), "R")
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if VERBOSE:
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print("\n".join(["".join("#" if col else "." for col in row) for row in beams]))
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# part 1
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answer_1 = sum(sum(map(bool, row)) for row in beams)
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print(f"answer 1 is {answer_1}")
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# part 2
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n_rows, n_cols = len(layout), len(layout[0])
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cases: list[tuple[tuple[int, int], Direction]] = []
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for row in range(n_rows):
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cases.append(((row, 0), "R"))
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cases.append(((row, n_cols - 1), "L"))
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for col in range(n_cols):
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cases.append(((0, col), "D"))
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cases.append(((n_rows - 1, col), "U"))
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answer_2 = max(
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sum(sum(map(bool, row)) for row in propagate(layout, start, direction))
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for start, direction in cases
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)
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print(f"answer 2 is {answer_2}")
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