2024 Day 05 part 2 re-written to not sort twice.

fmmr · Dec 5, 2024 · 6bc6836 · 6bc6836
1 parent 6c6da0b
commit 6bc6836
Showing 1 changed file with 7 additions and 4 deletions.
diff --git a/src/main/kotlin/no/rodland/advent_2024/Day05.kt b/src/main/kotlin/no/rodland/advent_2024/Day05.kt
@@ -26,10 +26,13 @@ class Day05(val input: List<String>) : Day<Int, Int, Pair<Map<Int, Set<Int>>, Li
     }
 
     override fun partTwo(): Int {
-        return pages
-            .filterNot { it.valid() }
-            .map { it.sort() }
-            .sumOf { it[it.size / 2] }
+        // only sorting once
+        return pages.map { it.sort() }.zip(pages).filter { it.first != it.second }.map { it.first }.sumOf { it[it.size / 2] }
+        // more readable
+        //        return pages
+        //            .filterNot { it.valid() }
+        //            .map { it.sort() }
+        //            .sumOf { it[it.size / 2] }
     }
 
     private fun List<Int>.valid(): Boolean = sort() == this