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y2022/p18.py

@@ -0,0 +1,36 @@
+def move(pt):
+    x, y, z = pt
+    for dx in [1, 0, -1]:
+        for dy in [1, 0, -1]:
+            for dz in [1, 0, -1]:
+                if abs(dx) + abs(dy) + abs(dz) == 1:
+                    yield x + dx, y + dy, z + dz
+
+
+def is_outside(pt, outside=set(), inside=set(), tune_f=150):
+    edge = {pt}
+    seen = set()
+    while True:
+        edge = {adj_pt for pt in edge for adj_pt in move(pt)} - seen - cubes
+        seen |= edge
+        if seen & outside or len(edge) > tune_f:
+            outside |= seen
+            return True
+        if seen & inside or not edge:
+            inside |= seen
+            return False
+
+
+def solve(is_outside=lambda *args: True):
+    surface = 0
+    for pt in cubes:
+        for adj_pt in move(pt):
+            if adj_pt not in cubes and is_outside(adj_pt):
+                surface += 1
+    return surface
+
+
+text = open(0).read()
+cubes = {tuple(map(int, ln.split(','))) for ln in text.splitlines()}
+print(solve())
+print(solve(is_outside))