Day 6.

src/aoc2025/Day06.kt

@@ -0,0 +1,56 @@
+package aoc2025
+
+import println
+import readInput
+import splitLongs
+
+/*
+--- Day 6: Trash Compactor ---
+https://adventofcode.com/2025/day/6
+*/
+fun main() {
+
+    val inlineTestInput = """
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +
+"""
+
+    fun part1(input: List<String>): Long {
+        val numbers = input.dropLast(1).map { it.splitLongs().toLongArray() }.toList()
+        val ops = input.last().split(" ").filter(String::isNotBlank)
+        return ops.withIndex().sumOf { (c, op) -> if (op == "+") numbers.sumOf { it[c] } else numbers.fold(1L) { acc, row -> acc * row[c] } }
+    }
+
+    fun part2(input: List<String>): Long {
+        val numbers = ArrayList<LongArray>()
+        val maxLineLength = input.maxOf { it.length }
+        val spaceMask = BooleanArray(maxLineLength)
+        input.forEach { it.withIndex().filter { (_, ch) -> ch != ' ' }.forEach { (c, _) -> spaceMask[c] = true } }
+        val numColl = ArrayList<Long>()
+        for (c in 0 until maxLineLength) {
+            if (spaceMask[c]) numColl.add(input.dropLast(1).map { it[c] }.joinToString("").trim().toLong())
+            if (!spaceMask[c] || c == maxLineLength - 1) {
+                numbers.add(numColl.toLongArray())
+                numColl.clear()
+            }
+        }
+        return input.last().split(" ").filter(String::isNotBlank).withIndex()
+            .sumOf { (c, op) -> if (op == "+") numbers[c].sum() else numbers[c].fold(1L) { acc, row -> acc * row } }
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = inlineTestInput.trim().reader().readLines()
+    //val testInput = readInput("aoc2025/Day06_test")
+    val testInputPart1Result = part1(testInput)
+    println("Part 1 Test: $testInputPart1Result")
+    val testInputPart2Result = part2(testInput)
+    println("Part 2 Test: $testInputPart2Result")
+    check(testInputPart1Result == 4277556L)
+    check(testInputPart2Result == 3263827L)
+
+    val input = readInput("aoc2025/Day06")
+    part1(input).println()
+    part2(input).println()
+}