Day 18.

2022/day18.py

@@ -0,0 +1,53 @@
+# -*- encoding: utf-8 -*-
+
+import sys
+from typing import FrozenSet
+
+import numpy as np
+
+xyz = np.asarray(
+    [
+        tuple(int(x) for x in row.split(","))  # type: ignore
+        for row in sys.stdin.read().splitlines()
+    ]
+)
+
+xyz = xyz - xyz.min(axis=0) + 1
+
+cubes = np.zeros(xyz.max(axis=0) + 3, dtype=bool)
+cubes[xyz[:, 0], xyz[:, 1], xyz[:, 2]] = True
+
+n_dims = len(cubes.shape)
+
+faces = [(-1, 0, 0), (1, 0, 0), (0, -1, 0), (0, 1, 0), (0, 0, -1), (0, 0, 1)]
+
+answer_1 = sum(
+    1 for x, y, z in xyz for dx, dy, dz in faces if not cubes[x + dx, y + dy, z + dz]
+)
+print(f"answer 1 is {answer_1}")
+
+visited = np.zeros_like(cubes, dtype=bool)
+queue = [(0, 0, 0)]
+
+n_faces = 0
+while queue:
+    x, y, z = queue.pop(0)
+
+    if visited[x, y, z]:
+        continue
+
+    visited[x, y, z] = True
+
+    for dx, dy, dz in faces:
+        nx, ny, nz = x + dx, y + dy, z + dz
+        if not all(n >= 0 and n < cubes.shape[i] for i, n in enumerate((nx, ny, nz))):
+            continue
+
+        if visited[nx, ny, nz]:
+            continue
+
+        if cubes[nx, ny, nz]:
+            n_faces += 1
+        else:
+            queue.append((nx, ny, nz))
+print(f"answer 2 is {n_faces}")