mango sour

y2021/p19.py

+from itertools import combinations, product
+
+
+def manhattan(p1, p2):
+    return tuple(abs(a - b) for a, b in zip(p1, p2))
+
+
+def find_shared_transpose(pts):
+    new = {manhattan(a, b): a for a, b in combinations(pts, 2)}
+    deltas = [
+        [(a - b) for a, b in zip(constellations[k], new[k])]
+        for k in set(constellations) & set(new)
+    ]
+    if deltas:
+        return [max(t, key=t.count) for t in zip(*deltas)]
+
+
+def overlap(pts):
+    for fx, fy, fz in product([1, -1], [1, -1], [1, -1]):
+        flipped = {(x * fx, y * fy, z * fz) for x, y, z in pts}
+        if deltas := find_shared_transpose(flipped):
+            dx, dy, dz = deltas
+            transposed = {(x + dx, y + dy, z + dz) for x, y, z in flipped}
+            if len(all_beacons & transposed) >= 12:
+                update_state((-dx, -dy, -dz), transposed)
+                return True
+
+
+def update_state(scanner, beacons):
+    all_scanners.add(scanner)
+    all_beacons.update(beacons)
+    new = {manhattan(a, b): a for a, b in combinations(all_beacons, 2)}
+    constellations.update(new)
+
+
+def transform(step, pts):
+    if step % 3 == 0:
+        pts = [pt[::-1] for pt in pts]
+    return [pt[1:] + pt[:1] for pt in pts]
+
+
+text = open(0).read()
+reference, *readings = [
+    [tuple(int(n) for n in ln.split(',')) for ln in scnr.splitlines()[1:]]
+    for scnr in text.split('\n\n')
+]
+all_scanners = set()
+all_beacons = set()
+constellations = {}
+update_state((0, 0, 0), reference)
+for step in range(30):
+    readings = [transform(step, pts) for pts in readings if not overlap(pts)]
+print(len(all_beacons))
+print(max(sum(manhattan(a, b)) for a, b in combinations(all_scanners, 2)))