My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Update solution for 2023/23
Store seen state as a bitfield instead of a set when computing the
longest path to improve runtime by around 30%.
+8
-3
+8
-3
2023/day23.py
+8
-3
2023/day23.py
···
39
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def longest_path(graph, start, end, part_2=False):
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-
horizon = [(start, 0, set())]
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+
BITMASK_MAPPING = {k: i for i, k in enumerate(graph)}
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+
horizon = [(start, 0, 0b0)]
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best = 0
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while horizon:
···
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best = max(best, dist)
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continue
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-
if curr in seen:
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+
mask = (1 << BITMASK_MAPPING[curr])
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+
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+
if seen & mask:
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continue
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+
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+
new_seen = seen | mask
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for neighbour, weight in graph[curr]:
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-
horizon.append((neighbour, dist + weight, seen | set([curr])))
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+
horizon.append((neighbour, dist + weight, new_seen))
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return best
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