Solved day19 part 2

Author: Gentleman1983

build.gradle

@@ -4,7 +4,7 @@ plugins {
 
 // project meta data
 group 'de.havox_design.aoc2023'
-version '0.18.6'
+version '0.18.7'
 
 // Switch to gradle "all" distribution.
 wrapper {

day19/src/main/kotlin/de/havox_design/aoc2023/day19/Day19.kt

@@ -1,5 +1,7 @@
 package de.havox_design.aoc2023.day19
 
+import java.util.*
+
 class Day19(private var filename: String) {
     private val ICON_ACCEPT = "A"
     private val ICON_REJECT = "R"
@@ -28,8 +30,49 @@ class Day19(private var filename: String) {
             .sumOf { it.total() }
     }
 
-    fun solvePart2(): Long =
-        167409079868000L
+    fun solvePart2(): Long {
+        val (rules) = readInput()
+        val results = mutableListOf<RangeAssignment>()
+        val queue = linkedListOf(RangeAssignment() to ICON_START)
+
+        while (queue.isNotEmpty()) {
+            val (current, label) = queue.removeFirst()
+
+            when (label) {
+                ICON_ACCEPT -> {
+                    results.add(current)
+                    continue
+                }
+
+                ICON_REJECT -> continue
+            }
+
+            val rule = rules[label]!!
+            val result = rule
+                .decisions
+                .runningFold(Triple(current, current, label)) { (_, falseValue), condition ->
+                    falseValue
+                        .split(condition)
+                        .let { (a, b) -> Triple(a, b, condition.successLabel) }
+                }
+                .drop(1)
+            result
+                .map { it.first to it.third }
+                .filter { it.first.isValid() }
+                .toCollection(queue)
+            when {
+                result.last().second.isValid() -> {
+                    queue.add(result.last().second to rule.elseRule)
+                }
+            }
+        }
+
+        return results
+            .sumOf { it.sum() }
+    }
+
+    private fun <T> linkedListOf(vararg elements: T) =
+        elements.toCollection(LinkedList())
 
     private fun readInput(): Pair<Map<String, SortRule>, List<Assignment>> {
         val input = getResourceAsText(filename)

day19/src/main/kotlin/de/havox_design/aoc2023/day19/RangeAssignment.kt

@@ -0,0 +1,47 @@
+package de.havox_design.aoc2023.day19
+
+data class RangeAssignment(
+    val xMin: Long = 1L,
+    val xMax: Long = 4000L,
+    val mMin: Long = 1L,
+    val mMax: Long = 4000L,
+    val aMin: Long = 1L,
+    val aMax: Long = 4000L,
+    val sMin: Long = 1L,
+    val sMax: Long = 4000L
+) {
+    fun split(condition: Condition): Pair<RangeAssignment, RangeAssignment> =
+        when (condition.field) {
+            'x' -> when (condition.lessThen) {
+                true -> copy(xMax = condition.value - 1) to copy(xMin = condition.value)
+                else -> copy(xMin = condition.value + 1) to copy(xMax = condition.value)
+            }
+
+            'm' -> when (condition.lessThen) {
+                true -> copy(mMax = condition.value - 1) to copy(mMin = condition.value)
+                else -> copy(mMin = condition.value + 1) to copy(mMax = condition.value)
+            }
+
+            'a' -> when (condition.lessThen) {
+                true -> copy(aMax = condition.value - 1) to copy(aMin = condition.value)
+                else -> copy(aMin = condition.value + 1) to copy(aMax = condition.value)
+            }
+
+            's' -> when (condition.lessThen) {
+                true -> copy(sMax = condition.value - 1) to copy(sMin = condition.value)
+                else -> copy(sMin = condition.value + 1) to copy(sMax = condition.value)
+            }
+
+            else -> error("Invalid state")
+        }
+
+
+    fun isValid() =
+        xMin <= xMax
+                && mMin <= mMax
+                && aMin <= aMax
+                && sMin <= sMax
+
+    fun sum() =
+        (xMax - xMin + 1) * (mMax - mMin + 1) * (aMax - aMin + 1) * (sMax - sMin + 1)
+}