My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2024/16
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2024/day16.py
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2024/day16.py
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import heapq
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import fileinput
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from collections import defaultdict
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from utils import Point, DIRS, E
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# Read problem input.
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BOARD = {}
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for y, line in enumerate(fileinput.input()):
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for x, c in enumerate(line.strip()):
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p = Point(x, y)
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BOARD[p] = '#' if c == '#' else '.'
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if c == 'S':
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START = p
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elif c == 'E':
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END = p
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# Best-first search around the maze.
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horizon = [(0, START, E, [])]
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seen = {}
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best_score = 1e9
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best_paths = defaultdict(list)
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while horizon:
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score, pos, d, path = heapq.heappop(horizon)
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if seen.get((pos, d), 1e9) < score:
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continue
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if pos == END:
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best_score = min(best_score, score)
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best_paths[score].append(path + [pos])
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seen[pos, d] = score
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for dd in DIRS:
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np = pos + dd
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if dd == -d:
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continue
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if dd == d and BOARD.get(np) == '.':
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heapq.heappush(horizon, (score + 1, np, dd, [pos] + path))
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elif BOARD.get(np) == '.':
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heapq.heappush(horizon, (score + 1001, np, dd, [pos] + path))
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nice_tiles = set()
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for path in best_paths[best_score]:
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nice_tiles |= set(path)
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print("Part 1:", best_score)
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print("Part 2:", len(nice_tiles))
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