68 lines
2.1 KiB
Python
68 lines
2.1 KiB
Python
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# SPDX-License-Identifier: MIT
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# Copyright (c) 2020 Akumatic
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#
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# https://adventofcode.com/2020/day/17
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from itertools import product
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def read_file() -> list:
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with open(f"{__file__.rstrip('code.py')}input.txt", "r") as f:
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return [list(line.strip()) for line in f.readlines()]
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def parse_input(input: list) -> set:
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active_cubes = set()
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for y in range(len(input)):
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for x in range(len(input[0])):
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if input[y][x] == "#":
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active_cubes.add((x, y, 0, 0))
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return active_cubes
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def simulate(active_cubes: set, size: int = 3, iterations: int = 6) -> int:
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assert 3 <= size <= 4
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# neighbor positions
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positions = product(range(-1, 2), repeat=size)
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if size == 4:
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npos = tuple(pos for pos in positions if pos != (0, 0, 0, 0))
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else: # size == 4
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npos = tuple((pos[0], pos[1], pos[2], 0) for pos in positions if pos != (0, 0, 0))
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# iterations
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for _ in range(iterations):
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next_active = set()
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neighbors = set()
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# check if active cubes stay active
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for cube in active_cubes:
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count = 0
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for n in npos:
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pos = tuple(cube[i] + n[i] for i in range(4))
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if pos in active_cubes:
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count += 1
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else:
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neighbors.add(pos)
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if 2 <= count <= 3:
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next_active.add(cube)
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# check neighbors of active cubes if they become active
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for cube in neighbors:
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count = 0
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for n in npos:
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pos = tuple(cube[i] + n[i] for i in range(4))
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if pos in active_cubes:
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count += 1
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if count == 3:
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next_active.add(cube)
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active_cubes = next_active
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return len(active_cubes)
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def part1(active_cubes: set) -> int:
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return simulate(active_cubes, 3)
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def part2(active_cubes: set) -> int:
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return simulate(active_cubes, 4)
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if __name__ == "__main__":
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input = read_file()
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data = parse_input(input)
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print(f"Part 1: {part1(data)}")
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print(f"Part 2: {part2(data)}")
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