Day 18

day18/part2.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+
+lines = (x.strip() for x in open("input.txt"))
+queue = [(0, 0, 0)]
+cnt = 0
+visited = set()
+cubes = set()
+
+for line in lines:
+    x, y, z = map(int, line.split(","))
+    cubes.add((x, y, z))
+
+while queue:
+    x, y, z = queue.pop(0)
+    for xn, yn, zn in ((1, 0, 0), (0, 1, 0), (0, 0, 1), (-1, 0, 0), (0, -1, 0), (0, 0, -1)):
+        neighbor = (x+xn, y+yn, z+zn)
+        if neighbor in cubes:
+            cnt += 1
+        elif neighbor not in visited and -2 <= neighbor[0] < 22 and -2 <= neighbor[1] < 22 and -2 <= neighbor[2] < 22:
+            queue.append(neighbor)
+            visited.add(neighbor)
+
+print(cnt)