AoC 2020: day17

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

2020-python/inputs/day_17

@@ -0,0 +1,8 @@
+##.#####
+#.##..#.
+.##...##
+###.#...
+.#######
+##....##
+###.###.
+.#.#.#..

2020-python/solutions/day_17.py

@@ -0,0 +1,95 @@
+"""AOC 2020 Day 17"""
+
+import pathlib
+import time
+import itertools
+
+TEST_INPUT = """.#.
+..#
+###"""
+
+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, dims: int) -> set:
+    """take input data and return the appropriate data structure"""
+    alive_cells = set()
+    zeros = [0]*(dims-2)
+    for x_cell, row in enumerate(input_data.split('\n')):
+        for y_cell, cell in enumerate(row):
+            if cell == '#':
+                alive_cells.add((x_cell, y_cell, *zeros))
+    return alive_cells
+
+def count_alive_neighbors(alive_cells: set, coords: tuple) -> int:
+    """return the number of alive neighbors of a given cell"""
+    alive = 0
+    ranges = ((c-1, c, c+1) for c in coords)
+    for cell in itertools.product(*ranges):
+        if cell in alive_cells:
+            alive += 1
+    if coords in alive_cells:
+        alive -= 1
+    return alive
+
+def get_cube_limits(alive_cells: set, dims: int) -> list:
+    """return cube bounds incremented for expansion"""
+    limits = list()
+    for i in range(dims):
+        low = float('Inf')
+        high = -float('Inf')
+        for row in alive_cells:
+            if row[i] < low:
+                low = row[i]
+            elif row[i] > high:
+                high = row[i]
+        limits.append(range(low-1, high+2))
+    return limits
+
+def step_cube(alive_cells: set, dims: int) -> set:
+    """return next step alive cells"""
+    next_step = set()
+    for cell in itertools.product(*get_cube_limits(alive_cells, dims)):
+        alive_neighbors = count_alive_neighbors(alive_cells, cell)
+        if (cell in alive_cells and alive_neighbors in (2, 3)) or alive_neighbors == 3:
+            next_step.add(cell)
+    return next_step
+
+def part1(input_data: str) -> int:
+    """part1 solver"""
+    cube = extract(input_data, 3)
+    for _ in range(6):
+        cube = step_cube(cube, 3)
+    return len(cube)
+
+def part2(input_data: str) -> int:
+    """part2 solver"""
+    cube = extract(input_data, 4)
+    for _ in range(6):
+        cube = step_cube(cube, 4)
+    return len(cube)
+
+def test_input_day_17():
+    """pytest testing function"""
+    assert part1(TEST_INPUT) == 112
+    assert part2(TEST_INPUT) == 848
+
+def test_bench_day_17(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)
+    print("Part 1: %d" % part1(input_data))
+    print("Part 2: %d" % part2(input_data))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()

README.md

@@ -26,3 +26,4 @@
 | [Day 14](https://adventofcode.com/2020/day/14) | [64.058ms](./2020-python/solutions/day_14.py)  | [56.398ms](./2020-python/solutions/day_14.py)  |
 | [Day 15](https://adventofcode.com/2020/day/15) | [4.463s](./2020-python/solutions/day_15.py)    | [718.712ms](./2020-python/solutions/day_15.py) |
 | [Day 16](https://adventofcode.com/2020/day/16) | [11.108ms](./2020-python/solutions/day_16.py)  | [2.903ms](./2020-python/solutions/day_16.py)   |
+| [Day 17](https://adventofcode.com/2020/day/17) | [743.804ms](./2020-python/solutions/day_17.py) | [836.255ms](./2020-python/solutions/day_17.py) |