Drastically improved the speed of day 5 part 2

tymscar · Dec 5, 2024 · 6e97c98 · 6e97c98
1 parent 0ed333e
commit 6e97c98
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Showing 2 changed files with 10 additions and 21 deletions.
diff --git a/2024/kotlin/build.gradle.kts b/2024/kotlin/build.gradle.kts
@@ -11,7 +11,6 @@ repositories {
 
 dependencies {
     testImplementation(kotlin("test"))
-    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4")
 }
 
 tasks.test {

diff --git a/2024/kotlin/src/main/kotlin/com/tymscar/day05/part2/part2.kt b/2024/kotlin/src/main/kotlin/com/tymscar/day05/part2/part2.kt
@@ -1,6 +1,5 @@
 package com.tymscar.day05.part2
 
-import kotlinx.coroutines.*
 
 private fun isValidUpdate(update: List<String>, orderingRules: Map<String, List<String>>): Boolean = update
     .withIndex()
@@ -18,11 +17,11 @@ private fun correctUpdate(update: List<String>, orderingRules: Map<String, List<
             correctedUpdate.withIndex().forEach { (index, page) ->
                 val previousPages = correctedUpdate.take(index)
                 val shouldBeLaterPages = orderingRules[page] ?: listOf()
-                if (previousPages.any { shouldBeLaterPages.contains(it) }) {
-                    val firstPageToSwap = previousPages.first { shouldBeLaterPages.contains(it) }
-                    val firstPageToSwapIndex = correctedUpdate.indexOf(firstPageToSwap)
-                    correctedUpdate.removeAt(firstPageToSwapIndex)
-                    correctedUpdate.add(index, firstPageToSwap)
+                val firstPageToSwapIndex = previousPages.indexOfFirst { shouldBeLaterPages.contains(it) }
+                if (firstPageToSwapIndex != -1) {
+                    val firstPageToSwap = previousPages[firstPageToSwapIndex]
+                    correctedUpdate[index] = firstPageToSwap
+                    correctedUpdate[firstPageToSwapIndex] = page
                     return@breaking
                 }
             }
@@ -42,18 +41,9 @@ fun solve(input: String): String {
         .map { it.groupValues[0].split(",") }
         .toList()
 
-    val invalidUpdates = pagesToCheck.filter { !isValidUpdate(it, orderingRules) }
-
-    return runBlocking {
-        val deferredResults = invalidUpdates.mapIndexed { index, update ->
-            async(Dispatchers.Default) {
-                val correctedUpdate = correctUpdate(update, orderingRules)
-                correctedUpdate[correctedUpdate.count() / 2].toInt()
-            }
-        }
-
-        val results = deferredResults.awaitAll()
-        return@runBlocking results.sum().toString()
-    }
-
+    return pagesToCheck
+        .filter { !isValidUpdate(it, orderingRules) }
+        .sumOf() { correctUpdate(it, orderingRules)
+        .let { it[it.count() / 2].toInt() } }
+        .toString()
 }