AoC 2020: day20

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

2020-python/solutions/day_20.py

@@ -0,0 +1,306 @@
+"""AOC 2020 Day 20"""
+
+import pathlib
+import time
+import collections
+import operator
+import itertools
+
+TEST_INPUT = """Tile 2311:
+..##.#..#.
+##..#.....
+#...##..#.
+####.#...#
+##.##.###.
+##...#.###
+.#.#.#..##
+..#....#..
+###...#.#.
+..###..###
+
+Tile 1951:
+#.##...##.
+#.####...#
+.....#..##
+#...######
+.##.#....#
+.###.#####
+###.##.##.
+.###....#.
+..#.#..#.#
+#...##.#..
+
+Tile 1171:
+####...##.
+#..##.#..#
+##.#..#.#.
+.###.####.
+..###.####
+.##....##.
+.#...####.
+#.##.####.
+####..#...
+.....##...
+
+Tile 1427:
+###.##.#..
+.#..#.##..
+.#.##.#..#
+#.#.#.##.#
+....#...##
+...##..##.
+...#.#####
+.#.####.#.
+..#..###.#
+..##.#..#.
+
+Tile 1489:
+##.#.#....
+..##...#..
+.##..##...
+..#...#...
+#####...#.
+#..#.#.#.#
+...#.#.#..
+##.#...##.
+..##.##.##
+###.##.#..
+
+Tile 2473:
+#....####.
+#..#.##...
+#.##..#...
+######.#.#
+.#...#.#.#
+.#########
+.###.#..#.
+########.#
+##...##.#.
+..###.#.#.
+
+Tile 2971:
+..#.#....#
+#...###...
+#.#.###...
+##.##..#..
+.#####..##
+.#..####.#
+#..#.#..#.
+..####.###
+..#.#.###.
+...#.#.#.#
+
+Tile 2729:
+...#.#.#.#
+####.#....
+..#.#.....
+....#..#.#
+.##..##.#.
+.#.####...
+####.#.#..
+##.####...
+##..#.##..
+#.##...##.
+
+Tile 3079:
+#.#.#####.
+.#..######
+..#.......
+######....
+####.#..#.
+.#...#.##.
+#.#####.##
+..#.###...
+..#.......
+..#.###..."""
+
+MONSTER_PATTERN = (
+    '                  # ',
+    '#    ##    ##    ###',
+    ' #  #  #  #  #  #   '
+)
+
+def read_input(input_path: str) -> str:
+    """take input file path and return a str with the file's content"""
+    with open(input_path, 'r') as input_file:
+        input_data = input_file.read().strip()
+        return input_data
+
+def extract(input_data: str) -> dict:
+    """take input data and return the appropriate data structure"""
+    tiles = dict()
+    for tile in input_data.split('\n\n'):
+        parts = tile.split('\n')
+        tile_id = int(parts[0][5:-1])
+        tiles[tile_id] = parts[1:]
+    return tiles
+
+def edge(matrix: list, side: str) -> str:
+    """return a side of a matrix"""
+    if side == 'n':
+        return matrix[0]
+    if side == 's':
+        return matrix[-1]
+    if side == 'e':
+        return ''.join(map(operator.itemgetter(-1), matrix))
+    return ''.join(map(operator.itemgetter(0), matrix))
+
+def get_tiles_corners(tiles: dict) -> dict:
+    """return the corners of a set of tiles"""
+    matching_sides = collections.defaultdict(str)
+    corners = {}
+
+    for id_tile1, id_tile2 in itertools.combinations(tiles, 2):
+        tile1, tile2 = tiles[id_tile1], tiles[id_tile2]
+
+        for side_a in 'nsew':
+            for side_b in 'nsew':
+                edge_a, edge_b = edge(tile1, side_a), edge(tile2, side_b)
+
+                if edge_a == edge_b or edge_a == edge_b[::-1]:
+                    matching_sides[id_tile1] += side_a
+                    matching_sides[id_tile2] += side_b
+
+    for tid, sides in matching_sides.items():
+        if len(sides) == 2:
+            corners[tid] = sides
+
+    assert len(corners) == 4
+    return corners
+
+def rotate90(matrix: list) -> tuple:
+    """return the matrix rotated by 90"""
+    return tuple(''.join(column)[::-1] for column in zip(*matrix))
+
+def possible_orientations(matrix: list) -> list:
+    """return all possible orientations of a given matrix"""
+    orientations = [matrix]
+    for _ in range(3):
+        matrix = rotate90(matrix)
+        orientations.append(matrix)
+    return orientations
+
+def possible_arrangements(matrix: list) -> list:
+    """return all possible arrangements of a given matrix"""
+    arrangements = possible_orientations(matrix)
+    arrangements.extend(possible_orientations(matrix[::-1]))
+    return arrangements
+
+def strip_edges(matrix: list) -> list:
+    """return a matrix without it's edges"""
+    return [row[1:-1] for row in matrix[1:-1]]
+
+def matching_tile(tile: list, tiles: dict, side_a: str, side_b: str) -> list:
+    """return the adjacent tile of a given one"""
+    edge_a = edge(tile, side_a)
+
+    for other_id, other_tile in tiles.items():
+        if tile is other_tile:
+            continue
+
+        for other_arr in possible_arrangements(other_tile):
+            if edge_a == edge(other_arr, side_b):
+                tiles.pop(other_id)
+                return other_arr
+
+def matching_row(prev: list, tiles: dict, tiles_per_row: int) -> list:
+    """return matching tiles in the row of a given one"""
+    matching_tiles = [prev]
+    tile = prev
+    for _ in range(tiles_per_row - 1):
+        tile = matching_tile(tile, tiles, 'e', 'w')
+        matching_tiles.append(tile)
+    return matching_tiles
+
+def build_image(top_left_tile: list, tiles: dict, image_dimension: int) -> list:
+    """build an image of a set of tiles"""
+    first = top_left_tile
+    image = []
+
+    while 1:
+        image_row = matching_row(first, tiles, image_dimension)
+        image_row = map(strip_edges, image_row)
+        image.extend(map(''.join, zip(*image_row)))
+
+        if not tiles:
+            break
+
+        first = matching_tile(first, tiles, 's', 'n')
+
+    return image
+
+def count_pattern(image: list, pattern: tuple) -> int:
+    """return the number of times a given pattern appears in an image"""
+    pattern_h, pattern_w = len(pattern), len(pattern[0])
+    image_sz = len(image)
+    deltas = []
+
+    for row_index, row in enumerate(pattern):
+        for cell_index, cell in enumerate(row):
+            if cell == '#':
+                deltas.append((row_index, cell_index))
+
+    for img in possible_arrangements(image):
+        appearances = 0
+        for row_index in range(image_sz - pattern_h):
+            for cell_index in range(image_sz - pattern_w):
+                if all(img[row_index + dr][cell_index + dc] == '#' for dr, dc in deltas):
+                    appearances += 1
+
+        if appearances != 0:
+            return appearances
+
+def part1(entries: dict) -> int:
+    """part1 solver"""
+    corners = get_tiles_corners(entries)
+    corners_prod = 1
+    for tile_id in corners:
+        corners_prod *= tile_id
+    return corners_prod
+
+def part2(entries: dict) -> int:
+    """part2 solver"""
+    corners = get_tiles_corners(entries)
+    top_left_id, matching_sides = corners.popitem()
+    top_left = entries[top_left_id]
+
+    if matching_sides in ('ne', 'en'):
+        top_left = rotate90(top_left)
+    elif matching_sides in ('nw', 'wn'):
+        top_left = rotate90(rotate90(top_left))
+    elif matching_sides in ('sw', 'ws'):
+        top_left = rotate90(rotate90(rotate90(top_left)))
+
+    image_dimension = int(len(entries) ** 0.5)
+    entries.pop(top_left_id)
+
+    image = build_image(top_left, entries, image_dimension)
+    monster_cells = sum(row.count('#') for row in MONSTER_PATTERN)
+    water_cells = sum(row.count('#') for row in image)
+    n_monsters = count_pattern(image, MONSTER_PATTERN)
+
+    return water_cells - n_monsters * monster_cells
+
+def test_input_day_20():
+    """pytest testing function"""
+    entries = extract(TEST_INPUT)
+    assert part1(entries) == 20899048083289
+    assert part2(entries) == 273
+
+def test_bench_day_20(benchmark):
+    """pytest-benchmark function"""
+    benchmark(main)
+
+def main():
+    """main function"""
+    input_path = str(pathlib.Path(__file__).resolve().parent.parent) + "/inputs/" + str(pathlib.Path(__file__).stem)
+    start_time = time.time()
+    input_data = read_input(input_path)
+    entries = extract(input_data)
+    print("Part 1: %d" % part1(entries))
+    print("Part 2: %d" % part2(entries))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()

README.md

@@ -19,7 +19,7 @@
 | [Day 7](https://adventofcode.com/2020/day/7)   | [1.689ms](./2020-python/solutions/day_07.py)   | [1.565ms](./2020-python/solutions/day_07.py)   |
 | [Day 8](https://adventofcode.com/2020/day/8)   | [6.313ms](./2020-python/solutions/day_08.py)   | [794.417µs](./2020-python/solutions/day_08.py) |
 | [Day 9](https://adventofcode.com/2020/day/9)   | [7.220ms](./2020-python/solutions/day_09.py)   | [4.783ms](./2020-python/solutions/day_09.py)   |
-| [Day 10](https://adventofcode.com/2020/day/10) | [139.110us](./2020-python/solutions/day_10.py) | [98.594µs](./2020-python/solutions/day_10.py)  |
+| [Day 10](https://adventofcode.com/2020/day/10) | [139.110µs](./2020-python/solutions/day_10.py) | [98.594µs](./2020-python/solutions/day_10.py)  |
 | [Day 11](https://adventofcode.com/2020/day/11) | [2.879s](./2020-python/solutions/day_11.py)    | [419.447ms](./2020-python/solutions/day_11.py) |
 | [Day 12](https://adventofcode.com/2020/day/12) | [746.181µs](./2020-python/solutions/day_12.py) | [211.216µs](./2020-python/solutions/day_12.py) |
 | [Day 13](https://adventofcode.com/2020/day/13) | [122.107µs](./2020-python/solutions/day_13.py) | [100.671µs](./2020-python/solutions/day_13.py) |
@@ -29,7 +29,7 @@
 | [Day 17](https://adventofcode.com/2020/day/17) | [743.804ms](./2020-python/solutions/day_17.py) | [836.255ms](./2020-python/solutions/day_17.py) |
 | [Day 18](https://adventofcode.com/2020/day/18) | [10.263ms](./2020-python/solutions/day_18.py)  | [2.053ms](./2020-python/solutions/day_18.py)   |
 | [Day 19](https://adventofcode.com/2020/day/19) | [145.980ms](./2020-python/solutions/day_19.py) | [259.030ms](./2020-python/solutions/day_19.py) |
-| [Day 20](https://adventofcode.com/2020/day/19) |                                                |                                                |
+| [Day 20](https://adventofcode.com/2020/day/19) | [513.955ms](./2020-python/solutions/day_20.py) | [316.973ms](./2020-python/solutions/day_20.py) |
 | [Day 21](https://adventofcode.com/2020/day/21) | [2.177ms](./2020-python/solutions/day_21.py)   | [1.578ms](./2020-python/solutions/day_21.py)   |
 | [Day 22](https://adventofcode.com/2020/day/22) | [1.516s](./2020-python/solutions/day_22.py)    | [1.353s](./2020-python/solutions/day_22.py)    |
 | [Day 23](https://adventofcode.com/2020/day/23) | [14.754s](./2020-python/solutions/day_23.py)   | [3.572s](./2020-python/solutions/day_23.py)    |