Day 22 simpler version

Day22.cs

@@ -1,7 +1,6 @@
 #define Day22
 #if Day22
 using System.Text.RegularExpressions;
-using AoC2021;
 
 var regex = new Regex(@"(?<turn>on|off) x=(?<xstart>-?\d+)\.\.(?<xend>-?\d+),y=(?<ystart>-?\d+)\.\.(?<yend>-?\d+),z=(?<zstart>-?\d+)\.\.(?<zend>-?\d+)");
 
@@ -10,12 +9,26 @@ var changes = File.ReadAllLines("day22/input")
     .Select(From)
     .ToList();
 
-
 PartOne(changes);
 PartTwo(changes);
+PartTwoSimpler(changes);
+
+void PartTwoSimpler(List<Change> changes) {
+    var onCuboids = new List<Cuboid>();
+
+    foreach (var change in changes) {
+        var newOnCuboids = onCuboids.Where(c => !c.Outside(change)).Select(c => c.CutCommonPart(change)).ToList();
+        if (change.turnOn) {
+            onCuboids.Add(new Cuboid() {from = change.from, to = change.to, negative = false});
+        }
+        onCuboids.AddRange(newOnCuboids);
+    }
+
+    var total = onCuboids.Select(c => c.NumberOfCubes()).Sum();
+    Console.WriteLine(total);
+}
 
 void PartTwo(List<Change> changes) {
-    int i = 0;
     var onCuboids = new List<Cuboid>();
 
     foreach (var change in changes) {
@@ -68,6 +81,8 @@ Change From(Match m) {
 record Change(bool turnOn, Point from, Point to);
 record Point(int x, int y, int z);
 class Cuboid {
+
+    public bool negative { get; set; } // used for part two simpler version only
     public Point from { get; set; }
     public Point to { get; set; }
 
@@ -77,7 +92,7 @@ class Cuboid {
                                        && change.from.z <= from.z && change.to.z >= to.z;
     }
 
-    bool Outside(Change change) {
+    public bool Outside(Change change) {
         return change.to.x < from.x || change.from.x > to.x
                                     || change.to.y < from.y || change.from.y > to.y
                                     || change.to.z < from.z || change.from.z > to.z;
@@ -88,7 +103,8 @@ class Cuboid {
         long y = to.y - from.y + 1;
         long z = to.z - from.z + 1;
 
-        return x * y * z;
+        long total = x * y * z;
+        return negative ? -total : total;
     }
     
     public List<Cuboid> Cut(Change change) {
@@ -169,5 +185,25 @@ class Cuboid {
 
         return newCuboids;
     }
+    
+    public Cuboid CutCommonPart(Change change) {
+        if (Outside(change)) {
+            throw new Exception();
+        }
+
+        return new Cuboid() {
+            negative = !this.negative,
+            from = new Point(
+                Math.Max(from.x, change.from.x),
+                Math.Max(from.y, change.from.y),
+                Math.Max(from.z, change.from.z)
+            ),
+            to = new Point(
+                Math.Min(to.x, change.to.x),
+                Math.Min(to.y, change.to.y),
+                Math.Min(to.z, change.to.z)
+            )
+        };
+    }
 }
 #endif