mirror of
https://github.com/Threnklyn/advent-of-code-go.git
synced 2026-05-18 19:13:27 +02:00
alexchao26
215 lines
7.8 KiB
Python
215 lines
7.8 KiB
Python
diff_map: dict[str, tuple[int, int]] = {
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"^": (-1, 0),
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"v": (1, 0),
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"<": (0, -1),
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">": (0, 1),
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}
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def part1(input: str) -> int:
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input_parts = input.split("\n\n")
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grid = [list(line) for line in input_parts[0].splitlines()]
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row: int = 0
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col: int = 0
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for r in range(len(grid)):
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for c in range(len(grid[0])):
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if grid[r][c] == "@":
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row = r
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col = c
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instructions = "".join(input_parts[1].splitlines())
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for inst in instructions:
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diff = diff_map[inst]
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next_row, next_col = row + diff[0], col + diff[1]
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match grid[next_row][next_col]:
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case "#":
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# blocked
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continue
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case ".":
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grid[row][col] = "."
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grid[next_row][next_col] = "@"
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row, col = next_row, next_col
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case "O":
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# attempt push, keep moving in direction of diff until a . or # is hit...
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not_obstacle_row, not_obstacle_col = next_row, next_col
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while grid[not_obstacle_row][not_obstacle_col] == "O":
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not_obstacle_row += diff[0]
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not_obstacle_col += diff[1]
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# if it's a wall "#", nothing moves, so only check for empty spaces "."
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if grid[not_obstacle_row][not_obstacle_col] == ".":
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grid[not_obstacle_row][not_obstacle_col] = "O"
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grid[next_row][next_col] = "@"
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grid[row][col] = "."
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row, col = next_row, next_col
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case _:
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raise Exception("unhandled grid type: ", grid[next_row][next_col])
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# print("\n".join(["".join(row) for row in grid]))
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# 100 times its distance from the top edge of the map plus its distance from the left edge of the map
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# 0-indexed so same as indices in 2D array
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gps_sum: int = 0
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for r in range(len(grid)):
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for c in range(len(grid[0])):
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if grid[r][c] == "O":
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gps_sum += r * 100 + c
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return gps_sum
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def part2(input: str) -> int:
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input_parts = input.split("\n\n")
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input_parts[0] = input_parts[0].replace("O", "[]")
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input_parts[0] = input_parts[0].replace(".", "..")
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input_parts[0] = input_parts[0].replace("#", "##")
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input_parts[0] = input_parts[0].replace("@", "@.")
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grid = [list(line) for line in input_parts[0].splitlines()]
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row: int = 0
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col: int = 0
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for r in range(len(grid)):
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for c in range(len(grid[0])):
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if grid[r][c] == "@":
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row = r
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col = c
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# print("\n".join(["".join(row) for row in grid]))
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instructions = "".join(input_parts[1].splitlines())
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for inst in instructions:
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# first see what's in the next space we want to move into...
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diff = diff_map[inst]
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next_row, next_col = row + diff[0], col + diff[1]
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match grid[next_row][next_col]:
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case "#":
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continue
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case ".":
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grid[row][col] = "."
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row += diff[0]
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col += diff[1]
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grid[row][col] = "@"
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case "[" | "]":
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# handle left and right separately because they only push one row of boxes
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# at this point row == next_row
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if inst in "<>":
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# copy-pasta from part 1
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not_obstacle_col = next_col
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while grid[next_row][not_obstacle_col] in "[]":
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not_obstacle_col += diff[1]
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# if it's a wall "#", nothing moves, so only check for empty spaces "."
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# move everything over towards the diff direction
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if grid[next_row][not_obstacle_col] == ".":
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for c in range(not_obstacle_col, col, -1 * diff[1]):
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grid[row][c] = grid[row][c - diff[1]]
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# move robot..
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grid[next_row][next_col] = "@"
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grid[row][col] = "."
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row, col = next_row, next_col
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else:
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# push boxes up or down, use a stack to maintain the reverse order of boxes that
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# MAY get moved
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coords_to_check: list[tuple[int, int]] = [
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(row, col),
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]
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to_check_index: int = 0
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is_blocked: bool = False
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while to_check_index < len(coords_to_check):
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front = coords_to_check[to_check_index]
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to_check_index += 1
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# variable masking is no bueno, but i guess it's fine here
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next_row, next_col = front[0] + diff[0], front[1] + diff[1]
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next_value = grid[next_row][next_col]
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if next_value == "#":
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is_blocked = True
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break
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if next_value == "[":
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coords_to_check.append((next_row, next_col))
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coords_to_check.append((next_row, next_col + 1))
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if next_value == "]":
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coords_to_check.append((next_row, next_col))
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coords_to_check.append((next_row, next_col - 1))
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# if "." then do nothing... no need to check
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# move everything towards diff if nothing was blocked
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# in reverse order to avoid overwrites
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if not is_blocked:
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# didn't prevent duplicate adds in the "checking" stage, so just no-op them here
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moved_set: set[tuple[int, int]] = set()
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for coord in reversed(coords_to_check):
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if coord in moved_set:
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continue
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moved_set.add(coord)
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next_row, next_col = coord[0] + diff[0], coord[1] + diff[1]
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grid[next_row][next_col], grid[coord[0]][coord[1]] = (
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grid[coord[0]][coord[1]],
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grid[next_row][next_col],
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)
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row, col = next_row, next_col
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case _:
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raise Exception("unexpected grid value: ", grid[next_row][next_col])
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# print("\n".join(["".join(row) for row in grid]))
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gps_sum: int = 0
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for r in range(len(grid)):
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for c in range(len(grid[0])):
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if grid[r][c] == "[":
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gps_sum += r * 100 + c
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return gps_sum
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small_example = """########
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#..O.O.#
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##@.O..#
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#...O..#
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#.#.O..#
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#...O..#
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#......#
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########
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<^^>>>vv<v>>v<<"""
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example = """##########
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#..O..O.O#
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#......O.#
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#.OO..O.O#
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#..O@..O.#
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#O#..O...#
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#O..O..O.#
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#.OO.O.OO#
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#....O...#
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##########
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<vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
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vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
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><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
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<<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
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^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
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^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
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>^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
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<><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
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^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
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v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^"""
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input = open("input.txt").read().strip()
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print(f"part1 small_example: {part1(small_example)} want 2028")
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print(f"part1 example: {part1(example)} want 10092")
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print(f"part1: {part1(input)} want 1413675")
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print(f"part2 example: {part2(example)} want 9021")
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print(f"part2: {part2(input)} want 1399772")
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