73 lines
1.8 KiB
Python
73 lines
1.8 KiB
Python
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#!/usr/bin/env python
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import itertools
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import sys
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from collections.abc import Iterator
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from typing import NamedTuple
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class Point(NamedTuple):
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x: int
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y: int
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def neighbours(self) -> Iterator["Point"]:
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for dx, dy in (
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(-1, 0),
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(1, 0),
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(0, -1),
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(0, 1),
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):
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yield Point(self.x + dx, self.y + dy)
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DIMS = 5
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def solve(input: str) -> int:
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def parse(input: list[str]) -> frozenset[Point]:
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return frozenset(
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Point(x, y)
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for x, line in enumerate(input)
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for y, c in enumerate(line)
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if c == "#"
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)
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def step(bugs: frozenset[Point]) -> frozenset[Point]:
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res: set[Point] = set()
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for p in map(Point._make, itertools.product(range(DIMS), range(DIMS))):
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neighbours = len(set(p.neighbours()) & bugs)
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# Bug dies if not exactly one neighbour
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if p in bugs and neighbours != 1:
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continue
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# An empty space stays empty if it doesn't have 1 or 2 neighbours
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if p not in bugs and neighbours not in (1, 2):
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continue
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res.add(p)
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return frozenset(res)
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def biodiversity(bugs: frozenset[Point]) -> int:
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res = 0
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for x, y in itertools.product(range(DIMS), range(DIMS)):
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res |= (Point(x, y) in bugs) << (x * DIMS + y)
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return res
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bugs = parse(input.splitlines())
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layouts: set[frozenset[Point]] = set()
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while True:
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layouts.add(frozenset(bugs))
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bugs = step(bugs)
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if bugs in layouts:
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return biodiversity(bugs)
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assert False # Sanity check
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def main() -> None:
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input = sys.stdin.read()
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print(solve(input))
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if __name__ == "__main__":
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main()
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