2024 - Day 15 - still part 1 - but re-written to hopefully be compati…

…ble with part 2.

src/main/kotlin/no/rodland/advent_2024/Day15.kt

@@ -25,42 +25,86 @@ class Day15(val input: List<String>) : Day<Long, Long, Pair<Pair<Pos, Cave>, Lis
             .sum().toLong()
     }
 
-    private fun getRest(d: Direction, robot: Pos): List<Pos> = when (d) {
-        Direction.NORTH -> (robot.y downTo 0).map { Pos(robot.x, it) }
-        Direction.SOUTH -> (robot.y..<height).map { Pos(robot.x, it) }
-        Direction.WEST -> (robot.x downTo 0).map { Pos(it, robot.y) }
-        Direction.EAST -> (robot.x..<width).map { Pos(it, robot.y) }
+    override fun partTwo(): Long {
+        return 2
     }
 
-    private fun List<Pos>.changes(cave: Cave, d: Direction, robot: Pos): Map<Pos, Char> {
-        val chars = map { cave[it] }
-        val firstSpace = chars.indexOf('.')
-        val firstWall = chars.indexOf('#')
-        if (firstWall > -1 && firstWall < firstSpace) {
-            return emptyMap()
-        }
-        if (firstSpace == -1) {
-            return emptyMap()
+    private fun getRest(cave: Cave, d: Direction, robot: Pos): Set<Pos> {
+        val set = mutableSetOf<Pos>()
+        val queue = ArrayDeque<Pos>()
+        queue.add(robot)
+        while (queue.isNotEmpty()) {
+            val p = queue.removeFirst()
+            when (cave[p]) {
+                'O', '@' -> {
+                    set.add(p)
+                    queue.add(p.next(d))
+                }
+
+                '#' -> {
+                    return emptySet()
+                }
+
+                '.' -> {
+                    set.add(p)
+                }
+
+//                ']' -> {
+//                    set.add(p)
+//                    val side = Pos(p.x - 1, p.y)
+//                    set.add(side)
+//                    val pnext = p.next(d)
+//                    val sidenext = side.next(d)
+//                    if (pnext !in queue) set.add(pnext)
+//                    if (sidenext !in queue) set.add(sidenext)
+//                }
+//
+//                '[' -> {
+//                    set.add(p)
+//                    val side = Pos(p.x + 1, p.y)
+//                    set.add(side)
+//                    val pNext = p.next(d)
+//                    val sideNext = side.next(d)
+//                    if (pNext !in queue) set.add(pNext)
+//                    if (sideNext !in queue) set.add(sideNext)
+//                }
+
+                else -> error("Unexpected character: ${cave[p]}")
+            }
         }
-        var i = 0
-        return (listOf('.') + (1..firstSpace).map { chars[it - 1] }).associateBy { robot.next(d, i++) }
+        val possible = true
+        return if (possible) set else emptySet()
+    }
+
+    private fun Set<Pos>.changes(cave: Cave, d: Direction, robot: Pos): Map<Pos, Char> {
+
+        val clearAll = map { p -> p to '.' }.toMap()
+        val newValues = map { p -> p.next(d) to cave[p] }.toMap()
+        // XXX probably something I can do here
+        return clearAll.mapValues { (k, v) -> newValues[k] ?: v }
+
+
+//        val chars = map { cave[it] }
+//        var i = 0
+//        val old = if (isEmpty()) {
+//            emptyMap()
+//        } else {
+//            (listOf('.') + (1..<size).map { chars[it - 1] }).associateBy { robot.next(d, i++) }
+//        }
+//        return old
     }
 
     private fun Cave.move(d: Direction, robot: Pos): Pos {
-        val line: List<Pos> = getRest(d, robot)
-        return line
-            .changes(this, d, robot)
+        val line: Set<Pos> = getRest(this, d, robot)
+        val changes = line.changes(this, d, robot)
+        return changes
             .mapNotNull { (p, c) ->
                 this[p] = c
                 if (c == '@') p else null
             }
             .firstOrNull() ?: robot
     }
 
-    override fun partTwo(): Long {
-        return 2
-    }
-
     override fun List<String>.parse(): Pair<Pair<Pos, Cave>, List<Direction>> {
         val (map, move) = joinToString("\n").split("\n\n")
         var start = Pos(0, 0)

src/test/kotlin/no/rodland/advent_2024/Day15Test.kt

@@ -29,7 +29,7 @@ internal class Day15Test {
         resultTwo,
         { Day15(data15) },
         { Day15(test15) },
-        numTestPart1 = 3,
+        numTestPart1 = 5,
         numTestPart2 = 1
     )