From 3bfb101052c41045704436eb04930cd0dca85602 Mon Sep 17 00:00:00 2001
From: dece <shgck@pistache.land>
Date: Thu, 6 Jan 2022 20:08:52 +0100
Subject: [PATCH] Day 22

---
 2021/day22.py | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 2021/day22.py

diff --git a/2021/day22.py b/2021/day22.py
new file mode 100644
index 0000000..3de2408
--- /dev/null
+++ b/2021/day22.py
@@ -0,0 +1,59 @@
+with open("input22.txt") as f:
+    lines = [line.rstrip() for line in f]
+steps = []
+for line in lines:
+    toggle, coords = line.split()
+    xr, yr, zr = (
+        tuple(map(int, coord[2:].split("..")))
+        for coord in coords.split(",")
+    )
+    steps.append((toggle == "on", (xr, yr, zr)))
+
+
+def print_volume(cuboids):
+    num_on = sum(
+        (x2 - x1 + 1) * (y2 - y1 + 1) * (z2 - z1 + 1)
+        for (x1, x2), (y1, y2), (z1, z2) in cuboids
+    )
+    print(num_on)
+
+
+cuboids = []
+for index, (toggle, step_cuboid) in enumerate(steps):
+    next_cuboids = []
+    (sx1, sx2), (sy1, sy2), (sz1, sz2) = step_cuboid
+    for cuboid in cuboids:
+        # If this cuboid does not intersect with our step, skip it.
+        if not all(
+            not (a1 > b2 or b1 > a2)
+            for (a1, a2), (b1, b2) in zip(cuboid, step_cuboid)
+        ):
+            next_cuboids.append(cuboid)
+            continue
+        (cx1, cx2), (cy1, cy2), (cz1, cz2) = cuboid
+        # Create a new sliced cube for each intersecting plane.
+        # Probably cleaner to do proper cuboid intersection but pffffff
+        if cx1 <= sx2 <= cx2:
+            next_cuboids.append(((sx2 + 1, cx2), (cy1, cy2), (cz1, cz2)))
+            cx2 = sx2
+        if cx1 <= sx1 <= cx2:
+            next_cuboids.append(((cx1, sx1 - 1), (cy1, cy2), (cz1, cz2)))
+            cx1 = sx1
+        if cy1 <= sy2 <= cy2:
+            next_cuboids.append(((cx1, cx2), (sy2 + 1, cy2), (cz1, cz2)))
+            cy2 = sy2
+        if cy1 <= sy1 <= cy2:
+            next_cuboids.append(((cx1, cx2), (cy1, sy1 - 1), (cz1, cz2)))
+            cy1 = sy1
+        if cz1 <= sz2 <= cz2:
+            next_cuboids.append(((cx1, cx2), (cy1, cy2), (sz2 + 1, cz2)))
+            cz2 = sz2
+        if cz1 <= sz1 <= cz2:
+            next_cuboids.append(((cx1, cx2), (cy1, cy2), (cz1, sz1 - 1)))
+            cz1 = sz1
+    if toggle:
+        next_cuboids.append(step_cuboid)
+    cuboids = next_cuboids
+    if index == 19:
+        print_volume(cuboids)
+print_volume(cuboids)