83 lines
2.3 KiB
Python
83 lines
2.3 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 typing import List, NamedTuple, Set, Tuple
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class Point(NamedTuple):
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x: int
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y: int
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Algorithm = List[bool]
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Image = Set[Point]
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def solve(input: List[str]) -> int:
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def parse() -> Tuple[Algorithm, Image]:
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algo_str, blank, *image_str = input
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assert blank == "" # Sanity check
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assert len(algo_str) == 512 # Sanity check
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algo = [c == "#" for c in algo_str]
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image = {
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Point(i, j)
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for i in range(len(image_str))
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for j in range(len(image_str[0]))
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if image_str[i][j] == "#"
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}
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return algo, image
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def do_step(algo: Algorithm, image: Image, step: int) -> Image:
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min_x, max_x = min(p.x for p in image), max(p.x for p in image)
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min_y, max_y = min(p.y for p in image), max(p.y for p in image)
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def color(p: Point) -> bool:
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# Always return true if we *know* that it is lit
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if p in image:
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return True
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# Return early if the rules don't lead to a flashing infinity case
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flashes_infinity = algo[0] and not algo[-1]
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if not flashes_infinity:
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return False
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# Pixels in proximity to the image are assumed to change their state normally
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if min_x <= p.x <= max_x and min_y <= p.y <= max_y:
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return False
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# Odd indices have a "lit infinity" which turns off, and vice versa
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return (step % 2) == 1
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def bits(p: Point) -> int:
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x, y = p
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res = 0
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for dx, dy in itertools.product(range(-1, 1 + 1), repeat=2):
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res = (res << 1) + color(Point(x + dx, y + dy))
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return res
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# We know the image we care for cannot grow by more than 1 per turn
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xs, ys = range(min_x - 1, max_x + 1 + 1), range(min_y - 1, max_y + 1 + 1)
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res: Image = set()
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for p in map(Point._make, itertools.product(xs, ys)):
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if algo[bits(p)]:
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res.add(p)
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return res
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rules, image = parse()
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for i in range(50):
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image = do_step(rules, image, i)
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return len(image)
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def main() -> None:
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input = [line.strip() for line in sys.stdin.readlines()]
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print(solve(input))
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if __name__ == "__main__":
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main()
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