Solved day14 part 2

Author: Gentleman1983

build.gradle

@@ -4,7 +4,7 @@ plugins {
 
 // project meta data
 group 'de.havox_design.aoc2023'
-version '0.13.3'
+version '0.13.4'
 
 // Switch to gradle "all" distribution.
 wrapper {

day14/src/main/kotlin/de/havox_design/aoc2023/day14/Day14.kt

@@ -7,8 +7,39 @@ class Day14(private var filename: String) {
             .northLoad()
             .toLong()
 
-    fun solvePart2(): Long =
-        64L
+    fun solvePart2(numberOfCycles: Int = 1000000000): Long {
+        val matrix = Matrix(getResourceAsText(filename))
+        val cycleMap: MutableMap<Int, String> = mutableMapOf(0 to matrix.toString())
+        var cycleIndex = 0
+        var cycleLength = 0
+
+        for (index in 1..numberOfCycles) {
+            matrix.cycle()
+            when {
+                cycleMap.containsValue(matrix.toString()) -> {
+                    cycleIndex = cycleMap
+                        .filterValues { it == matrix.toString() }
+                        .keys
+                        .single()
+                    cycleLength = index - cycleIndex
+                    break
+                }
+
+                else -> {
+                    cycleMap[index] = matrix.toString()
+                }
+            }
+        }
+
+        val pointInCycle = (numberOfCycles - cycleIndex) % cycleLength
+        val actualIndex = cycleIndex + pointInCycle
+
+        return cycleMap[actualIndex]!!
+            .split("\n")
+            .let(::Matrix)
+            .northLoad()
+            .toLong()
+    }
 
     private fun getResourceAsText(path: String): List<String> =
         this.javaClass.classLoader.getResourceAsStream(path)!!.bufferedReader().readLines()

day14/src/main/kotlin/de/havox_design/aoc2023/day14/Matrix.kt

@@ -4,6 +4,15 @@ data class Matrix(val matrix: MutableList<CharArray>) {
     private val ICON_ROUND_STONE = 'O'
     private val ICON_SQUARE_STONE = '#'
 
+    fun cycle(cycles: Int = 1): Matrix = apply {
+        repeat(cycles) {
+            rollNorth()
+                .rollWest()
+                .rollSouth()
+                .rollEast()
+        }
+    }
+
     fun rollNorth(): Matrix =
         apply {
             matrix
@@ -30,6 +39,66 @@ data class Matrix(val matrix: MutableList<CharArray>) {
                 }
         }
 
+    fun rollSouth(): Matrix =
+        apply {
+            matrix
+                .first()
+                .indices
+                .forEach { columnIndex ->
+
+                    matrix
+                        .indices
+                        .joinToString("") { rowIndex ->
+                            matrix[rowIndex][columnIndex].toString()
+                        }
+                        .split(ICON_SQUARE_STONE)
+                        .joinToString(ICON_SQUARE_STONE.toString()) {
+                            it
+                                .toCharArray()
+                                .sorted()
+                                .joinToString("")
+                        }
+
+                        .forEachIndexed { rowIndex, c ->
+                            matrix[rowIndex][columnIndex] = c
+                        }
+                }
+        }
+
+    fun rollWest(): Matrix =
+        apply {
+            matrix
+                .forEachIndexed { rowIndex, row ->
+                    matrix[rowIndex] = row
+                        .joinToString("")
+                        .split(ICON_SQUARE_STONE)
+                        .joinToString(ICON_SQUARE_STONE.toString()) {
+                            it
+                                .toCharArray()
+                                .sortedDescending()
+                                .joinToString("")
+                        }
+                        .toCharArray()
+                }
+        }
+
+    fun rollEast(): Matrix =
+        apply {
+            matrix
+                .forEachIndexed { rowIndex, row ->
+                    matrix[rowIndex] = row
+                        .joinToString("")
+                        .split(ICON_SQUARE_STONE)
+                        .joinToString(ICON_SQUARE_STONE.toString()) {
+                            it
+                                .toCharArray()
+                                .sorted()
+                                .joinToString("")
+                        }
+                        .toCharArray()
+                }
+        }
+
     fun northLoad(): Int =
         matrix
             .first()