distance

y2021/p22.py

 import re
 
 
-def intersect(cube, other):
-    return not (
-        cube[1] <= other[0] or
-        cube[0] >= other[1] or
-        cube[3] <= other[2] or
-        cube[2] >= other[3] or
-        cube[5] <= other[4] or
-        cube[4] >= other[5]
-    )
-
-
-def insert(cube, val):
-    to_break = {other for other in seen if intersect(cube, other)}
-    for cu in to_break:
-        seen.discard(cu)
-
-    xAs, xBs, yAs, yBs, zAs, zBs = zip(*{cube} | to_break)
-    xs = sorted(set(xAs + xBs))
-    ys = sorted(set(yAs + yBs))
-    zs = sorted(set(zAs + zBs))
-    N = 0
-    for i in range(len(xs) - 1):
-        for j in range(len(ys) - 1):
-            for k in range(len(zs) - 1):
-                new = (xs[i], xs[i + 1], ys[j], ys[j + 1], zs[k], zs[k + 1])
-
-                if val == 'off' and intersect(new, cube):
-                    seen.discard(new)
-
-                elif val == 'on' and intersect(new, cube):
-                    seen.add(new)
-
-                elif any(intersect(old, new) for old in to_break):
-                    seen.add(new)
-
-
-def volume(xA, xB, yA, yB, zA, zB):
-    return abs(xB - xA) * abs(yB - yA) * abs(zB - zA)
-
-
-text = open(0).read()
-cubes = {}
-for line in text.splitlines():
-    val = line.split()[0]
-    xA, xB, yA, yB, zA, zB = [int(n) for n in re.findall(r'-?\d+', line)]
-    cubes[xA, xB + 1, yA, yB + 1, zA, zB + 1] = val
-
-
-seen = set()
-for i, (cube, val) in enumerate(cubes.items(), 1):
-    insert(cube, val)
-    if i == 20:
-        print(sum(volume(*cu) for cu in seen))
-print(sum(volume(*cu) for cu in seen))
+def net_volume(cubes):
+    if not cubes:
+        return 0
+
+    (is_on, cube), *rest = cubes
+    if not is_on:
+        return net_volume(rest)
+
+    return volume(cube) - net_volume(intersect(cube, rest)) + net_volume(rest)
+
+
+def intersect(cube, rest):
+    return [
+        (True, new)
+        for _, other in rest
+        for new in [[f(a, b) for a, b, f in zip(cube, other, [max, min] * 3)]]
+        if volume(new)
+    ]
+
+
+def volume(cube):
+    xA, xB, yA, yB, zA, zB = cube
+    return max(xB - xA + 1, 0) * max(yB - yA + 1, 0) * max(zB - zA + 1, 0)
+
+
+cubes = tuple(
+    (line.split()[0] == 'on', [int(n) for n in re.findall(r'-?\d+', line)])
+    for line in open(0).read().splitlines()
+)
+print(net_volume(cubes[:20]))
+print(net_volume(cubes))