aoc/2020/17/17.py

def main(d):
	# create a set of tuples 
	seed = open('input.txt').read().split('\n')
	active = set(
		(d - 2) * (0,) + (i, j) # zero-pad coords
		for i, row in enumerate(seed)
		for j, cell in enumerate(row)
		if cell == '#'
	)

	# generate all tuples -1..1 in all dimensions
	neighboring = [()] # list contains empty tuple which will be iterated over
	for _ in range(d):
		neighboring = [
			_tuple + (offset,)
			for offset in [-1, 0, 1]
			for _tuple in neighboring
		]
	neighboring.remove(d * (0,)) # this is the center cell

	# do 6 iterations according to rules
	from collections import Counter
	for _ in range(6):
		active = set(
			_tuple
			for _tuple, count in Counter( # unpack the tuple and its count of neighboring active cells
				tuple(map(sum, zip(_tuple, offset))) # add neighbors kernel to each active cell
				for _tuple in active
				for offset in neighboring
			).items()
			if count == 3 or _tuple in active and count == 2
		)

	return len(active)

print(main(3), main(4))