Solved day15 part 2

Author: Gentleman1983

build.gradle

@@ -4,7 +4,7 @@ plugins {
 
 // project meta data
 group 'de.havox_design.aoc2023'
-version '0.14.4'
+version '0.14.5'
 
 // Switch to gradle "all" distribution.
 wrapper {

day15/src/main/kotlin/de/havox_design/aoc2023/day15/Box.kt

@@ -0,0 +1,15 @@
+package de.havox_design.aoc2023.day15
+
+data class Box(val code: Int, val lenses: MutableList<Lens> = mutableListOf()) {
+    fun add(lens: Lens) {
+        this
+            .lenses
+            .firstOrNull { it.label == lens.label }
+            ?.also { it.focalLength = lens.focalLength } ?: this.lenses.addLast(lens)
+    }
+    fun remove(label: String) {
+        this
+            .lenses
+            .removeIf { it.label == label }
+    }
+}

day15/src/main/kotlin/de/havox_design/aoc2023/day15/Day15.kt

@@ -9,8 +9,30 @@ class Day15(private var filename: String) {
             .sumOf { word -> calculateHash(word) }
             .toLong()
 
-    fun solvePart2(): Long =
-        145L
+    fun solvePart2(): Long {
+        val instructions = getResourceAsText(filename)[0]
+            .split(ELEMENT_DELIMITER)
+        val boxes = mutableMapOf<Int, Box>()
+
+        for (instruction in instructions) {
+            val (label, focalLength) = instruction.split('=', '-')
+            val hash = calculateHash(label)
+            when {
+                focalLength.isBlank() -> {
+                    boxes[hash]?.remove(label)
+                }
+                else -> {
+                    boxes.computeIfAbsent(hash) { Box(it) }.add(Lens(label, focalLength.toInt()))
+                }
+            }
+        }
+
+        return boxes
+            .filter { it.value.lenses.isNotEmpty() }
+            .flatMap { it.value.lenses.mapIndexed { idx, lens -> Triple(it.key + 1, idx + 1, lens) } }
+            .sumOf { it.first * it.second * it.third.focalLength }
+            .toLong()
+    }
 
     private fun calculateHash(word: String): Int =
         word

day15/src/main/kotlin/de/havox_design/aoc2023/day15/Lens.kt

@@ -0,0 +1,3 @@
+package de.havox_design.aoc2023.day15
+
+data class Lens(val label: String, var focalLength: Int)