Add solution to 2023-12-22

fuglede · fuglede · commit 10b898cf28aa · 2023-12-25T16:15:13.000+01:00
diff --git a/2023/day22/solutions.py b/2023/day22/solutions.py
@@ -0,0 +1,58 @@
+import re
+
+with open("input") as f:
+    ls = f.read().strip().split()
+
+ns = (map(int, re.findall("\d+", l)) for l in ls)
+bricks = []
+for x1, y1, z1, x2, y2, z2 in ns:
+    bricks.append(
+        {
+            (x, y, z)
+            for x in range(x1, x2 + 1)
+            for y in range(y1, y2 + 1)
+            for z in range(z1, z2 + 1)
+        }
+    )
+
+all_locs = set.union(*bricks)
+while True:
+    any_dropped = False
+    for i, brick in enumerate(bricks):
+        all_without = all_locs - brick
+        if all((x, y, z - 1) not in all_without for (x, y, z) in brick) and all(z > 1 for _, _, z in brick):
+            brick = {(x, y, z - 1) for (x, y, z) in brick}
+            bricks[i] = brick
+            all_locs = all_without | brick
+            any_dropped = True
+    if not any_dropped:
+        break
+
+depends_on = [
+    {
+        j
+        for j, brick2 in enumerate(bricks)
+        if i != j and any((x, y, z - 1) in brick2 for (x, y, z) in brick1)
+    }
+    for i, brick1 in enumerate(bricks)
+]
+
+# Part 1
+print(len(bricks) - len({list(v)[0] for v in depends_on if len(v) == 1}))
+
+# Part 2
+on_floor = {k for k, v in enumerate(depends_on) if not v}
+
+
+def num_fall_if_removed(removed):
+    unsupported = {
+        k
+        for k, v in enumerate(depends_on)
+        if not v - removed and k not in removed | on_floor
+    }
+    if not unsupported:
+        return 0
+    return len(unsupported) + num_fall_if_removed(removed | unsupported)
+
+
+print(sum(num_fall_if_removed({i}) for i in range(len(bricks))))
