From 5033bf5ce48e7278ba9877edb4b35e3243bb8fda Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20R=C3=B8dland?= <fmr@finn.no>
Date: Thu, 5 Dec 2024 12:39:30 +0100
Subject: [PATCH] 2024 Day 05 Part2

---
 .../kotlin/no/rodland/advent_2024/Day05.kt    | 46 +++++++++++++++----
 .../no/rodland/advent_2024/Day05Test.kt       |  6 +--
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/src/main/kotlin/no/rodland/advent_2024/Day05.kt b/src/main/kotlin/no/rodland/advent_2024/Day05.kt
index 9d2201d5..e7a4d23e 100644
--- a/src/main/kotlin/no/rodland/advent_2024/Day05.kt
+++ b/src/main/kotlin/no/rodland/advent_2024/Day05.kt
@@ -5,23 +5,49 @@ import no.rodland.advent.Day
 // template generated: 05/12/2024
 // Fredrik Rødland 2024
 
-class Day05(val input: List<String>) : Day<Int, Long, Pair<List<Pair<Int, Int>>, List<List<Int>>>> {
+class Day05(val input: List<String>) : Day<Int, Int, Pair<List<Pair<Int, Int>>, List<List<Int>>>> {
 
     private val parsed = input.parse()
     private val rules = parsed.first
     private val pages = parsed.second
 
     override fun partOne(): Int {
-       return  pages
-           .filter { list ->
-           val pairs = list.pairs()
-           pairs.all { it in rules }
-       }
-           .sumOf { it.middle() }
+        return pages
+            .filter { it.valid() }
+            .sumOf { it.middle() }
     }
 
-    override fun partTwo(): Long {
-        return 2
+    override fun partTwo(): Int {
+        return pages
+            .filterNot { it.valid() }
+            .map { it.reorder() }
+            .sumOf { it.middle() }
+    }
+
+    private fun List<Int>.valid() = pairs().all { it in rules }
+
+    private fun List<Int>.reorder(): List<Int> {
+        val breaking = pairs()
+            .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()
+        }
+    }
+
+    private fun List<Int>.move(element: Int, after: List<Int>): List<Int> {
+        val indexElement = indexOf(element)
+        val moveAfter = indexOfLast { it in after }
+        return subList(0, indexElement) + subList(indexElement + 1, moveAfter + 1) + element + subList(moveAfter + 1, size)
     }
 
     private fun List<Int>.middle(): Int = get(size / 2)
@@ -49,3 +75,5 @@ class Day05(val input: List<String>) : Day<Int, Long, Pair<List<Pair<Int, Int>>,
 }
 
 
+
+
diff --git a/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt b/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt
index 56ce3e36..c5589d6b 100644
--- a/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt
+++ b/src/test/kotlin/no/rodland/advent_2024/Day05Test.kt
@@ -16,9 +16,9 @@ internal class Day05Test {
     private val test05 = "2024/input_05_test.txt".readFile()
 
     private val resultTestOne = 143
-    private val resultTestTwo = 2L
+    private val resultTestTwo = 123
     private val resultOne = 5762
-    private val resultTwo = 2L
+    private val resultTwo = 4130
 
     val test = defaultTestSuiteParseOnInit(
         Day05(data05),
@@ -30,7 +30,7 @@ internal class Day05Test {
         { Day05(data05) },
         { Day05(test05) },
         numTestPart1 = 10,
-        numTestPart2 = 10,
+        numTestPart2 = 1,
     )
 
     @Nested