day(22): refactor

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/year2021/day22/Day22.kt

@@ -4,12 +4,21 @@ import product
 import readInput
 
 // region Global extensions
-fun IntRange.intersect(other: IntRange): IntRange = maxOf(first, other.first)..minOf(last, other.last)
+fun IntRange.intersect(other: IntRange): IntRange =
-fun IntRange.size(): Long = if (isEmpty()) 0L else last - first + 1L
+    maxOf(first, other.first)..minOf(last, other.last)
+
+val IntRange.size: Long
+    get() = if (isEmpty()) 0L else last - first + 1L
+
 fun IntRange.splitBy(other: IntRange): Sequence<IntRange> =
-    sequenceOf(first until other.first, other, other.last + 1..last)
+    sequenceOf(
+        first until other.first, other, other.last + 1..last
+    )
         .map { it.intersect(this) }
         .filterNot(IntRange::isEmpty)
+
+val IntRange.Companion.MAX_RANGE: IntRange
+    get() = Int.MIN_VALUE..Int.MAX_VALUE
 // endregion Global extensions
 
 // region State
@@ -24,20 +33,12 @@ fun String.toState(): State = when (this) {
 }
 // endregion State
 
-// region Point
-data class Point(val x: Int, val y: Int, val z: Int) {
-    fun within(xRange: IntRange, yRange: IntRange, zRange: IntRange): Boolean =
-        x in xRange && y in yRange && z in zRange
-}
-// endregion Point
-
 // region Cuboid
-data class Cuboid(val xRange: IntRange, val yRange: IntRange, val zRange: IntRange) {
+data class Cuboid(
-    val allPoints: Iterable<Point>
+    val xRange: IntRange, val yRange: IntRange, val zRange: IntRange
-        get() = xRange.flatMap { x -> yRange.flatMap { y -> zRange.map { z -> Point(x, y, z) } } }
+) {
-
     val size: Long
-        get() = xRange.size() * yRange.size() * zRange.size()
+        get() = xRange.size * yRange.size * zRange.size
 
     fun intersect(other: Cuboid): Cuboid = Cuboid(
         xRange = xRange.intersect(other.xRange),
@@ -45,7 +46,13 @@ data class Cuboid(val xRange: IntRange, val yRange: IntRange, val zRange: IntRan
         zRange = zRange.intersect(other.zRange),
     )
 
-    private fun isEmpty(): Boolean = xRange.isEmpty() || yRange.isEmpty() || zRange.isEmpty()
+    private fun intersectedBy(other: Cuboid): Boolean =
+        (xRange.first in other.xRange
+                && yRange.first in other.yRange
+                && zRange.first in other.zRange)
+
+    fun isEmpty(): Boolean =
+        xRange.isEmpty() || yRange.isEmpty() || zRange.isEmpty()
 
     operator fun minus(other: Cuboid): Set<Cuboid> {
         val overlap = this.intersect(other)
@@ -55,33 +62,26 @@ data class Cuboid(val xRange: IntRange, val yRange: IntRange, val zRange: IntRan
         } else if (overlap == this) {
             emptySet()
         } else {
-            buildSet {
+            product(
-                for ((xs, ys, zs) in product(
                 xRange.splitBy(overlap.xRange),
                 yRange.splitBy(overlap.yRange),
                 zRange.splitBy(overlap.zRange),
-                )) {
+            )
-                    if (
+                .map { (xs, ys, zs) -> Cuboid(xs, ys, zs) }
-                        xs.first !in overlap.xRange
+                .filter { !it.intersectedBy(overlap) }
-                        || ys.first !in overlap.yRange
+                .toSet()
-                        || zs.first !in overlap.zRange
-                    ) {
-                        add(Cuboid(xs, ys, zs))
-                    }
-                }
         }
     }
+
+    companion object {
+        val MAX_CUBOID =
+            Cuboid(IntRange.MAX_RANGE, IntRange.MAX_RANGE, IntRange.MAX_RANGE)
     }
 }
 // endregion Cuboid
 
 // region Step
-data class Step(val state: State, val cuboid: Cuboid) {
+data class Step(val state: State, val cuboid: Cuboid)
-    val allPoints: Iterable<Point>
-        get() = cuboid.allPoints
-
-    fun crop(cuboid: Cuboid): Step = this.copy(cuboid = this.cuboid.intersect(cuboid))
-}
 
 fun String.toStep(): Step {
     val (state, regions) = this.split(" ")
@@ -95,23 +95,21 @@ fun String.toStep(): Step {
 }
 // endregion Step
 
-fun part1(input: List<Step>): Int = input.fold(mutableSetOf<Point>()) { turnedOn, step ->
+// region Reactor
-    val croppedStep = step.crop(Cuboid(-50..50, -50..50, -50..50))
+data class Reactor(
-    when (step.state) {
+    val interestingCuboid: Cuboid = Cuboid.MAX_CUBOID,
-        State.On -> turnedOn.addAll(croppedStep.allPoints)
+    val cuboids: List<Cuboid> = emptyList()
-        State.Off -> turnedOn.removeAll(croppedStep.allPoints)
+) {
+    fun execute(step: Step): Reactor {
+        val affectedCuboid = interestingCuboid.intersect(step.cuboid)
+        if (affectedCuboid.isEmpty()) {
+            return this
         }
 
-    turnedOn
-}.size
-
-// region Reactor
-data class Reactor(val cuboids: List<Cuboid> = emptyList()) {
-    fun execute(step: Step): Reactor {
         // remove current one from turned on
-        val withoutStep = cuboids.flatMapTo(mutableListOf()) { it - step.cuboid }
+        val withoutStep = cuboids.flatMapTo(mutableListOf()) { it - affectedCuboid }
         if (step.state == State.On) {
-            withoutStep.add(step.cuboid)
+            withoutStep.add(affectedCuboid)
         }
 
         return copy(cuboids = withoutStep)
@@ -119,17 +117,24 @@ data class Reactor(val cuboids: List<Cuboid> = emptyList()) {
 }
 // endregion Reactor
 
-fun part2(input: List<Step>): Long = input.fold(Reactor()) { reactor, step ->
+val INIT_RANGE = -50..50
+fun part1(input: List<Step>): Long =
+    input.fold(Reactor(Cuboid(INIT_RANGE, INIT_RANGE, INIT_RANGE))) { reactor, step ->
         reactor.execute(step)
-}.cuboids.sumOf { it.size }
+    }.cuboids.sumOf { it.size }
+
+fun part2(input: List<Step>): Long =
+    input.fold(Reactor()) { reactor, step ->
+        reactor.execute(step)
+    }.cuboids.sumOf { it.size }
 
 fun main() {
     val smallerSample = readInput(22, "smaller_sample").map(String::toStep)
     val sample = readInput(22, "sample").map(String::toStep)
     val input = readInput(22, "input").map(String::toStep)
 
-    check(part1(smallerSample) == 39)
+    check(part1(smallerSample) == 39L)
-    check(part1(sample) == 590784)
+    check(part1(sample) == 590784L)
     println(part1(input))
 
     val rebootSample = readInput(22, "reboot_sample").map(String::toStep)