Merge branch 'feature/day19' into develop

0legg · 0legg · commit d900302d9be0 · 2024-12-18T21:10:02.000-08:00
diff --git a/year2024/src/main/kotlin/net/olegg/aoc/year2024/day19/Day19.kt b/year2024/src/main/kotlin/net/olegg/aoc/year2024/day19/Day19.kt
@@ -0,0 +1,60 @@
+package net.olegg.aoc.year2024.day19
+
+import net.olegg.aoc.someday.SomeDay
+import net.olegg.aoc.year2024.DayOf2024
+
+/**
+ * See [Year 2024, Day 19](https://adventofcode.com/2024/day/19)
+ */
+object Day19 : DayOf2024(19) {
+  override fun first(): Any? {
+    val (rawPatterns, rawTowels) = data.split("\n\n")
+
+    val patterns = rawPatterns.split(", ")
+
+    return rawTowels.lines().count { towel ->
+      val reachable = MutableList(towel.length + 1) { false }
+      reachable[0] = true
+
+      reachable.indices.forEach { index ->
+        if (reachable[index]) {
+          val tail = towel.substring(index)
+          patterns.forEach { pattern ->
+            if (tail.startsWith(pattern)) {
+              reachable[index + pattern.length] = true
+            }
+          }
+        }
+      }
+
+      reachable.last()
+    }
+  }
+
+  override fun second(): Any? {
+    val (rawPatterns, rawTowels) = data.split("\n\n")
+
+    val patterns = rawPatterns.split(", ")
+
+    return rawTowels.lines().sumOf { towel ->
+      val reachable = MutableList(towel.length + 1) { 0L }
+      reachable[0] = 1L
+
+      reachable.indices.forEach { index ->
+        val count = reachable[index]
+        if (count != 0L) {
+          val tail = towel.substring(index)
+          patterns.forEach { pattern ->
+            if (tail.startsWith(pattern)) {
+              reachable[index + pattern.length] += count
+            }
+          }
+        }
+      }
+
+      reachable.last()
+    }
+  }
+}
+
+fun main() = SomeDay.mainify(Day19)
