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day_20.py
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day_20.py
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from collections import defaultdict
from math import prod
import aoc_helper
raw = aoc_helper.fetch(20, year=2020)
def parse_raw():
tiles = raw.split("\n\n")
return dict(
(int(tile.splitlines()[0][5:-1]), tile.splitlines()[1:]) for tile in tiles
)
data = parse_raw()
def get_data():
edges = defaultdict(set)
neighbours = defaultdict(set)
for id, tile in data.items():
top_edge = tile[0]
neighbours[id] |= edges[top_edge]
for neighbour in edges[top_edge]:
neighbours[neighbour].add(id)
edges[top_edge].add(id)
neighbours[id] |= edges[top_edge[::-1]]
for neighbour in edges[top_edge[::-1]]:
neighbours[neighbour].add(id)
edges[top_edge[::-1]].add(id)
bottom_edge = tile[-1]
neighbours[id] |= edges[bottom_edge]
for neighbour in edges[bottom_edge]:
neighbours[neighbour].add(id)
edges[bottom_edge].add(id)
neighbours[id] |= edges[bottom_edge[::-1]]
for neighbour in edges[bottom_edge[::-1]]:
neighbours[neighbour].add(id)
edges[bottom_edge[::-1]].add(id)
left_edge = "".join(i[0] for i in tile)
neighbours[id] |= edges[left_edge]
for neighbour in edges[left_edge]:
neighbours[neighbour].add(id)
edges[left_edge].add(id)
neighbours[id] |= edges[left_edge[::-1]]
for neighbour in edges[left_edge[::-1]]:
neighbours[neighbour].add(id)
edges[left_edge[::-1]].add(id)
right_edge = "".join(i[-1] for i in tile)
neighbours[id] |= edges[right_edge]
for neighbour in edges[right_edge]:
neighbours[neighbour].add(id)
edges[right_edge].add(id)
neighbours[id] |= edges[right_edge[::-1]]
for neighbour in edges[right_edge[::-1]]:
neighbours[neighbour].add(id)
edges[right_edge[::-1]].add(id)
corners = [k for k, v in neighbours.items() if len(v) == 2]
return edges, neighbours, corners
def get(set):
return next(iter(set))
def part_one():
edges, neighbours, corners = get_data()
return prod(corners)
def flip_x(im):
return [row[::-1] for row in im]
def flip_y(im):
return im[::-1]
def rotate(im):
return [[im[x][y] for x in range(len(im[0]))] for y in range(len(im))]
def monsters(im):
monsters = 0
hashes = "\n".join("".join(row) for row in im).count("#")
for x in range(len(im[0]) - 18):
for y in range(len(im[0]) - 2):
if im[y][x : x + 20][18] != "#":
continue
if any(
monster == "#" and image != monster
for monster, image in zip("# ## ## ###", im[y + 1][x : x + 20])
):
continue
if any(
monster == "#" and image != monster
for monster, image in zip(" # # # # # # ", im[y + 2][x : x + 20])
):
continue
monsters += 1
return monsters, hashes - monsters * 15
def part_two():
edges, neighbours, corners = get_data()
rev_edges = defaultdict(set)
for k, v in edges.items():
for id in v:
rev_edges[id].add(k)
edge_tiles = len([k for k, v in neighbours.items() if len(v) == 3]) // 4
all_values = set.union(*neighbours.values())
grid = [
[all_values.copy() for i in range(edge_tiles + 2)]
for i in range(edge_tiles + 2)
]
grid[0][0] = {corners[0]}
grid[0][1] = {neighbours[corners[0]].pop()}
grid[1][0] = neighbours[corners[0]]
used = set.union(grid[0][0], grid[0][1], grid[1][0])
while any(len(v) > 1 for row in grid for v in row):
for y, row in enumerate(grid):
for x, poss in enumerate(row):
if len(poss) == 1:
continue
poss -= used
if x > 0:
poss &= set.union(*[neighbours[i] for i in row[x - 1]])
if y > 0:
poss &= set.union(*[neighbours[i] for i in grid[y - 1][x]])
if len(poss) == 1:
used |= poss
continue
image = []
for y in grid:
l_idx = get(y[0])
c_idx = get(y[1])
shared_side = rev_edges[l_idx] & rev_edges[c_idx]
tile = data[l_idx]
top_edge = "".join(tile[0])
bottom_edge = "".join(tile[-1])
left_edge = "".join(i[0] for i in tile)
right_edge = "".join(i[-1] for i in tile)
if top_edge in shared_side:
tile = flip_x(rotate(tile))
if bottom_edge in shared_side:
tile = rotate(tile)
if left_edge in shared_side:
tile = flip_x(tile)
edge = "".join(i[-1] for i in tile)
row = [tile]
for last, current in zip(y, y[1:]):
l_idx = get(last)
c_idx = get(current)
shared_side = rev_edges[l_idx] & rev_edges[c_idx]
tile = data[c_idx]
top_edge = "".join(tile[0])
bottom_edge = "".join(tile[-1])
left_edge = "".join(i[0] for i in tile)
right_edge = "".join(i[-1] for i in tile)
if top_edge in shared_side:
tile = rotate(tile)
if bottom_edge in shared_side:
tile = flip_x(rotate(tile))
if right_edge in shared_side:
tile = flip_x(tile)
my_edge = "".join(i[0] for i in tile)
my_right_edge = "".join(i[-1] for i in tile)
if my_edge == edge:
row.append(tile)
edge = my_right_edge
else:
row.append(tile[::-1])
edge = my_right_edge[::-1]
processed_row = [[] for i in row[0]]
for tile in row:
for prow, trow in zip(processed_row, tile):
prow.extend(trow[1:-1])
image.append(processed_row)
processed_image = []
c_top = "".join(image[0][0])
c_bottom = "".join(image[0][-1])
n_top = "".join(image[1][0])
n_bottom = "".join(image[1][-1])
if c_bottom in (n_top, n_bottom):
processed_image.extend(image[0][1:-1])
edge = c_bottom
else:
processed_image.extend(image[0][::-1][1:-1])
edge = c_top
for prev, current in zip(image, image[1:]):
c_top = "".join(current[0])
c_bottom = "".join(current[-1])
if c_top == edge:
processed_image.extend(current[1:-1])
edge = c_bottom
else: # this doesn't work for malformed inputs but why should it
processed_image.extend(flip_y(current)[1:-1])
edge = c_top
results = {}
results[result[0]] = (result := monsters(processed_image))[1]
results[result[0]] = (result := monsters(flip_y(processed_image)))[1]
results[result[0]] = (result := monsters(flip_x(processed_image)))[1]
results[result[0]] = (result := monsters(flip_x(flip_y(processed_image))))[1]
results[result[0]] = (result := monsters(rotate(processed_image)))[1]
results[result[0]] = (result := monsters(flip_y(rotate(processed_image))))[1]
results[result[0]] = (result := monsters(flip_x(rotate(processed_image))))[1]
results[result[0]] = (result := monsters(flip_x(flip_y(rotate(processed_image)))))[
1
]
return results[max(results)]
aoc_helper.lazy_submit(day=20, year=2020, solution=part_one)
aoc_helper.lazy_submit(day=20, year=2020, solution=part_two)