Day 19.

src/aoc2024/Day19.kt

@@ -0,0 +1,58 @@
+package aoc2024
+
+import println
+import readInput
+
+/*
+--- Day 19: Linen Layout ---
+https://adventofcode.com/2024/day/19
+*/
+fun main() {
+
+    val inlineTestInput = """
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb
+"""
+
+    fun rec(inp: String, towels: Array<String>): Boolean =
+        inp.isEmpty() || towels.any { inp.startsWith(it) && rec(inp.substring(it.length), towels) }
+
+    fun part1(input: List<String>): Int {
+        val towels = input[0].split(", ").toTypedArray()
+        return input.drop(2).count { rec(it, towels) }
+    }
+
+    val cache = HashMap<String, Long>()
+
+    fun rec2(inp: String, towels: Array<String>): Long =
+        if (inp.isEmpty()) 1 else cache.getOrPut(inp) {
+            towels.filter { inp.startsWith(it) }.sumOf { rec2(inp.substring(it.length), towels) }
+        }
+
+    fun part2(input: List<String>): Long {
+        val towels = input[0].split(", ").toTypedArray()
+        return input.drop(2).sumOf { rec2(it, towels) }
+    }
+
+    // test if implementation meets criteria from the description, like:
+    val testInput = inlineTestInput.trim().reader().readLines()
+    //val testInput = readInput("aoc2024/Day19_test")
+    val testInputPart1Result = part1(testInput)
+    println("Part 1 Test: $testInputPart1Result")
+    val testInputPart2Result = part2(testInput)
+    println("Part 2 Test: $testInputPart2Result")
+    check(testInputPart1Result == 6)
+    check(testInputPart2Result == 16L)
+
+    val input = readInput("aoc2024/Day19")
+    part1(input).println()
+    part2(input).println()
+}