2024 Day 05 Part2 - reversing list of elements to move - avoiding mul…

…tiple move-passes.
fmmr · Dec 5, 2024 · b576d7f · b576d7f
1 parent 40723fd
commit b576d7f
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diff --git a/src/main/kotlin/no/rodland/advent_2024/Day05.kt b/src/main/kotlin/no/rodland/advent_2024/Day05.kt
@@ -31,17 +31,17 @@ class Day05(val input: List<String>) : Day<Int, Int, Pair<List<Pair<Int, Int>>,
             .filterNot { it in rules }
             .groupBy({ it.first }, { it.second })
 
-        val fold = breaking.keys.fold(this) { acc, b ->
-            acc.move(b, breaking[b]!!)
-        }
-        return if (fold.valid()){
-            // println("yeah.       $this    $fold    $breaking")
-            fold
-        }else{
-            // still not right - just run it again
-            // println("reordering. $this    $fold    $breaking")
-            fold.reorder()
-        }
+        return breaking.keys.reversed().fold(this) { acc, b -> acc.move(b, breaking[b]!!) }
+
+        // if not reversing the keys above - multiple passes must be done to ensure we have a right-ordered list.
+        // by starting at the end we don't have to.
+        //        return if (fold.valid()) {
+        //             println("yeah.       $this    $fold    $breaking")
+        //        } else {
+        //            // still not right - just run it again
+        //             println("reordering. $this    $fold    $breaking")
+        //            fold.reorder()
+        //        }
     }
 
     private fun List<Int>.move(element: Int, after: List<Int>): List<Int> {

diff --git a/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt b/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt
@@ -30,7 +30,7 @@ internal class Day05Test {
         { Day05(data05) },
         { Day05(test05) },
         numTestPart1 = 10,
-        numTestPart2 = 1,
+        numTestPart2 = 10,
     )
 
     @Nested