aoc-8.py

challenge = """
......#....#
...#....0...
....#0....#.
..#....0....
....0....#..
.#....A.....
...#........
#......#....
........A...
.........A..
..........#.
..........#.
"""

challenge = challenge.split("\n")
challenge = [[x for x in c] for c in challenge if len(c) > 0]

nodes = {}

def is_aligned(left, right):
	if abs(left[0] - right[0]) == 1 or abs(left[1] - right[1]) == 1:
		if abs(left[0] - right[0]) == 1 and abs(left[1] - right[1]) == 1:
			return ("x", "y")
		elif abs(left[0] - right[0]) == 1:
			return ("x")
		elif abs(left[1] - right[1]) == 1:
			return ("y")
	return ()

aligned = set()


for idx in range(len(challenge)):
	for idy in range(len(challenge[idx])):
		value = challenge[idx][idy]

		if value != "." and value != "#":
			if value not in nodes:
				nodes[value] = []
			nodes[value].append((idx, idy))	

for node in nodes:
	nodes[node] = sorted(nodes[node], key = lambda v: v[0])

	for idx in range(len(nodes[node]) - 1):
		left, right = nodes[node][idx], nodes[node][idx + 1]

		result = is_aligned(left, right)

		aligned.add((left, right, result))

	nodes[node] = sorted(nodes[node], key = lambda v: v[1])

	for idx in range(len(nodes[node]) - 1):
		left, right = nodes[node][idx], nodes[node][idx + 1]

		result = is_aligned(left, right)

		aligned.add((left, right, result))

def distance(left, right):
	a, b = left
	c, d = right

	return ((((a - c) ** 2) + ((b - d) ** 2))) ** .5	

antinodes = set()

for pair in aligned:
	# find a position on the map where it is x distance from left and 2x distance from right
	left, right, axis = pair
	candidates = []

	if 'x' in axis:
		min_x = min(left, right, key = lambda v: v[0])[0]
		max_x = max(left, right, key = lambda v: v[0])[0]
		
		for idy in range(len(challenge[0])):
			candidates.append((min_x - 1, idy))
			candidates.append((max_x + 1, idy))
	if 'y' in axis:
		min_y = min(left, right, key = lambda v: v[1])[1]
		max_y = max(left, right, key = lambda v: v[1])[1]

		for idx in range(len(challenge)):
			candidates.append((idx, min_y - 1))
			candidates.append((idx, max_y + 1))

	for candidate in candidates:
		dl = distance(candidate, left)
		dr = distance(candidate, right)

		if candidate == (2,4):
			print(candidate, left, right, challenge[left[0]][left[1]], challenge[right[0]][right[1]])

		if candidate[0] < 0 or candidate[0] >= len(challenge) or candidate[1] < 0 or candidate[1] >= len(challenge[candidate[0]]):
			continue
		if (dl * 2 == dr) or (dr * 2 == dl):
			antinodes.add((candidate[0], candidate[1]))

for x in range(len(challenge)):
	for y in range(len(challenge[x])):
		if challenge[x][y] == "#":
			challenge[x][y] = "."

for x, y in antinodes:
	challenge[x][y] = f"#"

print(len(antinodes))

challenge = ["".join(c) for c in challenge]
for idx, line in enumerate(challenge):
	print(" ".join(line), idx)
for idx in range(len(challenge[0])):
	print(idx, end=" ")