1 files changed, 53 insertions, 0 deletions
diff --git a/translation.py b/translation.py
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+import sys
+import numpy as np
+import functools
+
+sys.setrecursionlimit(100000)
+
+# Part 1
+# cubes←⍎¨⊃⎕NGET'input'1
+cubes = [eval(f"({line})") for line in open("input").readlines()]
+
+# movements←{⍵,-⍵}↓(3 3⍴4↑1)
+movements = (lambda w: np.vstack([w, -w]))(np.identity(3, dtype=int))
+
+# sides←,cubes∘.+movements
+sides = [tuple(c + m) for c in cubes for m in movements]
+
+# ≢sides~cubes
+print(sum(1 for side in sides if side not in cubes))
+
+# Part 2
+# mins←(↑⌊/cubes)-1 1 1
+mins = tuple(min(c) - 1 for c in zip(*cubes))
+# maxs←(↑⌈/cubes)+1 1 1
+maxs = tuple(max(c) + 1 for c in zip(*cubes))
+# in_boundary←{0≡+/((⍵<mins),(⍵>maxs))}
+in_boundary = lambda c: 0 == functools.reduce(
+    lambda a, b: a + b,
+    (int(c[i] < mins[i] or c[i] > maxs[i]) for i in range(3)),
+    0,
+)
+# count←0
+count = 0
+
+
+def rec(left, right):
+    global count
+    # 0=≢⍵:count
+    if not right:
+        return count
+    # head←1↑⍵ ⋄ tail←1↓⍵
+    head, tail = right[0], right[1:]
+    # neighbors←movements+¨head
+    neighbors = [tuple(head + m) for m in movements]
+    # next←{(in_boundary¨⍵)/⍵}neighbors
+    next = set(filter(in_boundary, neighbors))
+    # count⊢←count+(+/{(↓⍵)∊cubes}¨neighbors)
+    count += sum((n in cubes) for n in neighbors)
+    # (⍺,head)∇((tail∪next)~⍺)
+    return rec(left | set([head]), list((set(tail) | next) - left))
+
+
+# cubes{...}↓maxs
+print(rec(set(cubes), [maxs]))