Day 18, not too neat, part 2

Signed-off-by: Rob Grant <rob.grant@nanoporetech.com>

day18/run.py

@@ -1,12 +1,47 @@
-from itertools import combinations_with_replacement 
-
 from inputs import REAL as data
 
-points = set(tuple(map(int, line.split(","))) for line in data.split("\n"))
-
+MANHATTAN_3D = ((1, 0, 0), (-1, 0, 0), (0, 1, 0), (0, -1, 0), (0, 0, 1), (0, 0, -1))
+
+CUBES = set(tuple(map(int, line.split(","))) for line in data.split("\n"))
+
+
+def face_count(c, cubes):
+    return sum((c[0] + xd, c[1] + yd, c[2] + zd) not in cubes for xd, yd, zd in MANHATTAN_3D)
+
 
-def face_count(p, points):
-    return sum((p[0] + xd, p[1] + yd, p[2] + zd) not in points for xd, yd, zd in ((1, 0, 0), (-1, 0, 0), (0, 1, 0), (0, -1, 0), (0, 0, 1), (0, 0, -1)))
+def face_count_in_steam(c, steam):
+    return sum((c[0] + xd, c[1] + yd, c[2] + zd) in steam for xd, yd, zd in MANHATTAN_3D)
+
+
+def fill_with_steam(cubes):
+    cubes_list = list(cubes)
+    x_min, y_min, z_min = cubes_list[0]
+    x_max, y_max, z_max = cubes_list[0]
+
+    for c in cubes_list[1:]:
+        x_min, x_max = min(x_min, c[0]), max(x_max, c[0])
+        y_min, y_max = min(y_min, c[1]), max(y_max, c[1])
+        z_min, z_max = min(z_min, c[2]), max(z_max, c[2])
+
+    steam = set()
+    cubes_touching_steam = set()
+
+    candidate_steam = [(x_min - 1, y_min - 1, z_min - 1)]
+    while candidate_steam:
+        s = candidate_steam.pop()
+        if s not in steam:
+            steam.add(s)
+            for dx, dy, dz in MANHATTAN_3D:
+                m = s[0] + dx, s[1] + dy, s[2] + dz
+                if (x_min - 1) <= m[0] <= (x_max + 1) and (y_min - 1) <= m[1] <= (y_max + 1) and (z_min - 1) <= m[2] <= (z_max + 1):
+                    if m in cubes:
+                        cubes_touching_steam.add(m)
+                    if m not in steam and m not in cubes:
+                        candidate_steam.append(m)
+
+    return cubes_touching_steam, steam
 
+cubes_touching_steam, steam = fill_with_steam(CUBES)
 
-print(f"Part 1: {sum(face_count(p, points) for p in points)}") 
+print(f"Part 1: {sum(face_count(c, CUBES) for c in CUBES)}") 
+print(f"Part 2: {sum(face_count_in_steam(c, steam) for c in cubes_touching_steam)}")