Maybe solution 2018-11, part 2 (Chronal Charge)

... but it does not terminate in a reasonable time.

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/year2018/day11/ChronalCharge.kt

@@ -1,21 +1,19 @@
 package de.ronny_h.aoc.year2018.day11
 
 import de.ronny_h.aoc.AdventOfCode
+import de.ronny_h.aoc.extensions.grids.Coordinates
 import de.ronny_h.aoc.extensions.grids.Grid
 import de.ronny_h.aoc.extensions.numbers.digit
 
 fun main() = ChronalCharge().run("34,13", "")
 
 class ChronalCharge : AdventOfCode<String>(2018, 11) {
     // start:  11:59
-    override fun part1(input: List<String>): String {
-        val grid = PowerCellGrid(input.single().toInt())
-        return grid.find3x3SquareWithLargestTotal()
-    }
+    override fun part1(input: List<String>): String =
+        PowerCellGrid(input.single().toInt()).find3x3SquareWithLargestTotal()
 
-    override fun part2(input: List<String>): String {
-        return ""
-    }
+    override fun part2(input: List<String>): String =
+        PowerCellGrid(input.single().toInt()).findSquareWithLargestTotal()
 }
 
 class PowerCellGrid(serialNumber: Int) : Grid<Int>(300, 300, -1000) {
@@ -29,19 +27,31 @@ class PowerCellGrid(serialNumber: Int) : Grid<Int>(300, 300, -1000) {
         }.last()
     }
 
+    fun findSquareWithLargestTotal(): String {
+        val max = (1..300)
+            .map { findSquareWithLargestTotalForSize(it) }
+            .maxBy { it.total }
+        return "${max.coordinates.col},${max.coordinates.row},${max.size}"  // X,Y,size
+    }
+
     fun find3x3SquareWithLargestTotal(): String {
-        val maxCoordinates = forEachCoordinates { coordinates, _ ->
-            val total = (0..2).sumOf { i ->
-                (0..2).sumOf { j ->
+        val maxCoordinates = findSquareWithLargestTotalForSize(3).coordinates
+        return "${maxCoordinates.col},${maxCoordinates.row}"  // X,Y
+    }
+
+    private data class Square(val coordinates: Coordinates, val size: Int, val total: Int)
+
+    private fun findSquareWithLargestTotalForSize(squareSize: Int): Square =
+        forEachCoordinates { coordinates, _ ->
+            val total = (0..<squareSize).sumOf { i ->
+                (0..<squareSize).sumOf { j ->
                     this[coordinates.row + i, coordinates.col + j]
                 }
             }
-            coordinates to total
+            Square(coordinates, squareSize, total)
         }
-            .maxBy { it.second }
-            .first
-        return "${maxCoordinates.col},${maxCoordinates.row}"  // X,Y
-    }
+            .maxBy { it.total }
+
 
     override fun Char.toElementType(): Int = digitToInt()
 }

src/test/kotlin/de/ronny_h/aoc/year2018/day11/ChronalChargeTest.kt

@@ -26,8 +26,7 @@ class ChronalChargeTest : StringSpec({
         ChronalCharge().part1(listOf("42")) shouldBe "21,61"
     }
 
-    "part 2" {
-        val input = listOf("")
-        ChronalCharge().part2(input) shouldBe ""
+    "part 2: For grid serial number 18, the largest total square is 16x16 with a top-left corner of 90,269" {
+        ChronalCharge().part2(listOf("18")) shouldBe "90,269,16"
     }
 })