Create day24.py

Author: elvinyhlee

day24.py

@@ -0,0 +1,106 @@
+EAST = 'e'
+WEST = 'w'
+SOUTHEAST = 'se'
+SOUTHWEST = 'sw'
+NORTHWEST = 'nw'
+NORTHEAST = 'ne'
+
+
+direction = {
+    EAST: (+2, 0),
+    WEST: (-2, 0),
+    SOUTHEAST: (+1, -1),
+    SOUTHWEST: (-1, -1),
+    NORTHEAST: (+1, +1),
+    NORTHWEST: (-1, +1),
+}
+
+
+def part1(tiles):
+    black_coord = set()
+
+    for tile in tiles:
+        coord = (0, 0)
+        for i in tile:
+            coord = (coord[0] + direction[i][0], coord[1] + direction[i][1])
+
+        if coord in black_coord:
+            black_coord.remove(coord)
+        else:
+            black_coord.add(coord)
+
+    return len(black_coord)
+
+
+def count_adjacent_black_tiles(coord: tuple, black_coord: set[tuple]) -> int:
+    return sum(
+        1 if (coord[0] + d[0], coord[1] + d[1]) in black_coord else 0
+        for d in direction.values()
+    )
+
+
+def part2(tiles):
+    # Copied from part 1
+    black_coord = set()
+
+    for tile in tiles:
+        coord = (0, 0)
+        for i in tile:
+            coord = (coord[0] + direction[i][0], coord[1] + direction[i][1])
+
+        if coord in black_coord:
+            black_coord.remove(coord)
+        else:
+            black_coord.add(coord)
+
+    # Core logic for part 2
+    for i in range(100):
+        new_black_coord = set()
+
+        min_x, max_x = float('inf'), float('-inf')
+        min_y, max_y = float('inf'), float('-inf')
+        for coord in black_coord:
+            min_x, max_x = min(min_x, coord[0]), max(max_x, coord[0])
+            min_y, max_y = min(min_y, coord[1]), max(max_y, coord[1])
+
+        for j in range(min_x - 2, max_x + 2 + 1):
+            for k in range(min_y - 1, max_y + 1 + 1):
+                coord = (j, k)
+                count = count_adjacent_black_tiles(coord, black_coord)
+
+                if coord in black_coord:
+                    if 0 < count <= 2:
+                        new_black_coord.add(coord)
+                elif count == 2:
+                    new_black_coord.add(coord)
+
+        black_coord = new_black_coord
+
+    return len(black_coord)
+
+
+def extract_data(lines):
+    tiles = []
+    for line in lines:
+        tile = []
+        ix = 0
+        while ix < len(line):
+            if line.startswith((EAST, WEST), ix):
+                tile.append(line[ix])
+                ix += 1
+            else:
+                tile.append(line[ix:ix+2])
+                ix += 2
+        tiles.append(tile)
+
+    return tiles
+
+
+with open('day24-data.txt') as f:
+    inputs = [
+        line
+        for line in f.read().splitlines()
+    ]
+
+    print(part1(extract_data(inputs)))
+    print(part2(extract_data(inputs)))