mirror of
https://github.com/Threnklyn/advent-of-code-go.git
synced 2026-05-18 19:13:27 +02:00
alexchao26
136 lines
3.5 KiB
Python
136 lines
3.5 KiB
Python
import heapq
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diffs: list[tuple[int, int]] = [
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(0, 1), # start at index 0 facing "east"/right
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(-1, 0), # up
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(0, -1), # left
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(1, 0), # down
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]
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def day16(input: str, part: int) -> int:
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grid = [list(line) for line in input.splitlines()]
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start_row: int = 0
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start_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] == "S":
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start_row = r
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start_col = c
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# i think i'd rather write a struct in go... these tuples are easy to make
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# but annoying to maintain in my head...
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# score, row, col, dir_index
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node: tuple[int, int, int, int, set[tuple[int, int]]] = (
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int(0),
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start_row,
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start_col,
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int(0),
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set(),
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)
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min_heap = [node]
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heapq.heapify(min_heap)
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coord_to_min_score: dict[tuple[int, int, int], int] = {}
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best_score: int = 1_000_000 # big enough to not interfere with actual input answer
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final_path_coords: set[tuple[int, int]] = set()
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while len(min_heap) > 0:
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popped = heapq.heappop(min_heap)
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# part2 exit once best_score is set down to the actual min value
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if popped[0] > best_score:
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continue
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# row, col, dir_index
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coord = (popped[1], popped[2], popped[3])
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if coord in coord_to_min_score:
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prev_score = coord_to_min_score[coord]
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# if previous score at this coord and direction is better then continue
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if popped[0] > prev_score:
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continue
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# update best score to reach this coord
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coord_to_min_score[coord] = popped[0]
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# end reached
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if grid[popped[1]][popped[2]] == "E":
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best_score = popped[0]
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final_path_coords |= popped[4]
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final_path_coords.add((popped[1], popped[2]))
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continue
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# in same direction
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diff = diffs[popped[3]]
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next = (
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popped[0] + 1,
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popped[1] + diff[0],
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popped[2] + diff[1],
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popped[3],
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popped[4] | {(popped[1], popped[2])},
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)
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if grid[next[1]][next[2]] in ".E":
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heapq.heappush(min_heap, next)
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# 90 deg turns
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heapq.heappush(
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min_heap,
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(popped[0] + 1000, popped[1], popped[2], (popped[3] + 1) % 4, popped[4]),
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)
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heapq.heappush(
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min_heap,
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(popped[0] + 1000, popped[1], popped[2], (popped[3] - 1) % 4, popped[4]),
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)
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if part == 1:
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return best_score
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return len(final_path_coords)
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example = """###############
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#.......#....E#
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#.#.###.#.###.#
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#.....#.#...#.#
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#.###.#####.#.#
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#.#.#.......#.#
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#.#.#####.###.#
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#...........#.#
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###.#.#####.#.#
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#...#.....#.#.#
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#.#.#.###.#.#.#
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#.....#...#.#.#
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#.###.#.#.#.#.#
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#S..#.....#...#
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###############"""
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example2 = """#################
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#...#...#...#..E#
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#.#.#.#.#.#.#.#.#
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#.#.#.#...#...#.#
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#.#.#.#.###.#.#.#
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#...#.#.#.....#.#
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#.#.#.#.#.#####.#
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#.#...#.#.#.....#
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#.#.#####.#.###.#
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#.#.#.......#...#
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#.#.###.#####.###
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#.#.#...#.....#.#
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#.#.#.#####.###.#
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#.#.#.........#.#
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#.#.#.#########.#
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#S#.............#
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#################"""
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input = open("input.txt").read().strip()
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print(f"day16 example: {day16(example, 1)} want 7036")
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print(f"day16 example2: {day16(example2,1)} want 11048")
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print(f"day16 actual: {day16(input,1)} want 83444")
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print(f"part2 example: {day16(example,2)} want 45")
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print(f"part2 example2: {day16(example2,2)} want 64")
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print(f"part2 actual: {day16(input,2)} want 483")
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