From 7f8a4ebb896336ba1308aec23d67d062c07dcfd4 Mon Sep 17 00:00:00 2001
From: Sven Weidauer <sven@5sw.de>
Date: Wed, 25 Dec 2024 12:49:52 +0100
Subject: [PATCH] Day 19 part 2

---
 2024/src/main/kotlin/day19.kt | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/2024/src/main/kotlin/day19.kt b/2024/src/main/kotlin/day19.kt
index b95c49c..ae16405 100644
--- a/2024/src/main/kotlin/day19.kt
+++ b/2024/src/main/kotlin/day19.kt
@@ -5,17 +5,22 @@ fun main() {
         .flatMap { it.split(",\\s*".toRegex()) }
         .toList()
 
-    val part1 = Sequence { iterator }.count { isPossible(it, towels) }
+    val patterns = Sequence { iterator }.toList()
+
+    val part1 = patterns.count { waysToMake(it, towels) > 0 }
     println("Part 1: $part1")
+
+    val part2 = patterns.sumOf { waysToMake(it, towels) }
+    println("Part 2: $part2")
 }
 
-private val patternMemo = mutableMapOf<String, Boolean>()
+private val patternMemo = mutableMapOf<String, Long>()
 
-fun isPossible(pattern: String, towels: List<String>): Boolean {
-    if (pattern.isEmpty()) return true
+fun waysToMake(pattern: String, towels: List<String>): Long {
+    if (pattern.isEmpty()) return 1
     return patternMemo.getOrPut(pattern) {
         towels
             .filter { pattern.startsWith(it) }
-            .any { isPossible(pattern.substring(it.length), towels) }
+            .fold(0) { acc, towel -> acc + waysToMake(pattern.substring(towel.length), towels) }
     }
 }