⭐⭐ Merry Christmas

Author: JesperDramsch

2020/day24.py

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+from util import Day
+from aocd import submit
+from collections import Counter
+
+# east, southeast, southwest, west, northwest, and northeast
+# e, se, sw, w, nw, and ne
+# pointy hex
+
+
+def preprocess(row):
+    return row.replace("", " ").strip().replace("n ", "n").replace("s ", "s").split(" ")
+
+directions = {
+    "ne": 1 + 0.5j,
+    "e": 1j,
+    "se": -1 + 0.5j,
+    "sw": -1 - 0.5j,
+    "w": -1j,
+    "nw": 1 - 0.5j,
+}
+
+
+def flip(row):
+    return sum((directions[char] for char in row))
+
+
+def get_neighbours(tile):
+    return [tile + val for val in directions.values()]
+
+
+def möve(state):
+    new_state = set()
+
+    around = Counter()
+    for tile in state:
+        neighbours = get_neighbours(tile)
+        count = 0
+        for n in neighbours:
+            if n in state:
+                count += 1   # neighbour black of this black tile
+            else:
+                around[n] += 1  # counts up one for the neighbouring tiles if white
+        # Any black tile with zero or more than 2 black tiles immediately adjacent to it is flipped to white.
+        if 0 < count < 3:
+            new_state.add(tile)
+
+    # Any white tile with exactly 2 black tiles immediately adjacent to it is flipped to black.
+    for k, v in around.items():
+        if v == 2:
+            new_state.add(k)
+
+    return new_state
+
+
+def hex_of_lyfe(state, moves):
+    for i in range(moves):
+        state = möve(state)
+        print(f"Move {i+1}: {len(state)}")
+    return len(state)
+
+
+def main(day, part=1):
+    day.apply(preprocess)
+    day.apply(flip)
+    count = Counter(day.data)
+    if part == 1:
+        out = sum((1 for _, v in count.items() if (v % 2)))
+    if part == 2:
+        start = set((k for k, v in count.items() if (v % 2)))
+        out = hex_of_lyfe(start, 100)
+    return out
+
+
+if __name__ == "__main__":
+    day = Day(24)
+    day.download()
+
+    day.load(typing=str)
+    p1 = main(day)
+    print(p1)
+    submit(p1, part="a", day=24, year=2020)
+
+    day.load(typing=str)
+    p2 = main(day, part=2)
+    print(p2)
+    submit(p2, part="b", day=24, year=2020)

2020/tests/test_day24.py

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+import sys
+import pytest
+
+sys.path.insert(0, ".")
+from util import Day
+from day24 import *
+
+@pytest.fixture(scope="function")
+def example():
+    day = Day(24)
+    data = """sesenwnenenewseeswwswswwnenewsewsw
+neeenesenwnwwswnenewnwwsewnenwseswesw
+seswneswswsenwwnwse
+nwnwneseeswswnenewneswwnewseswneseene
+swweswneswnenwsewnwneneseenw
+eesenwseswswnenwswnwnwsewwnwsene
+sewnenenenesenwsewnenwwwse
+wenwwweseeeweswwwnwwe
+wsweesenenewnwwnwsenewsenwwsesesenwne
+neeswseenwwswnwswswnw
+nenwswwsewswnenenewsenwsenwnesesenew
+enewnwewneswsewnwswenweswnenwsenwsw
+sweneswneswneneenwnewenewwneswswnese
+swwesenesewenwneswnwwneseswwne
+enesenwswwswneneswsenwnewswseenwsese
+wnwnesenesenenwwnenwsewesewsesesew
+nenewswnwewswnenesenwnesewesw
+eneswnwswnwsenenwnwnwwseeswneewsenese
+neswnwewnwnwseenwseesewsenwsweewe
+wseweeenwnesenwwwswnew"""
+
+    day.load(data, typing=str)
+    return day
+
+@pytest.fixture(scope="function")
+def day():
+    day = Day(24)
+    day.load(typing=str)
+    return day
+
+def test_example(example):
+    assert main(example, part=1) == 10
+
+def test_example_p2(example):
+    assert main(example, part=2) == 2208
+
+def test_part1(day):
+    assert main(day, part=1) == 326
+
+def test_part2(day):
+    assert main(day, part=2) == 3979