day 10 puzzle 2

src/day10/Painter.scala

@@ -0,0 +1,77 @@
+package day10
+
+import scala.collection.mutable.ArrayBuffer
+
+class Painter(startX: Int, startY: Int, excludeX: Int, excludeY: Int) extends Walker(startX, startY, excludeX, excludeY) {
+  def walk(grid: Array[Array[Byte]], zones: Array[Array[Int]], path: ArrayBuffer[(Int, Int)]): Unit = {
+    val prevX: Int = lastX
+    val prevY: Int = lastY
+    val curX: Int = x
+    val curY: Int = y
+    val curTile: Byte = grid(y)(x)
+    super.walk(grid)
+    val newX: Int = x
+    val newY: Int = y
+    val dx: Int = newX - prevX
+    val dy: Int = newY - prevY
+
+    // West-East
+    if (curTile == 5) {
+      // Going east
+      if (dx > 0) {
+        setZone(path, zones, curX, curY - 1, 1)
+        setZone(path, zones, curX, curY + 1, 2)
+
+        // Going west
+      } else {
+        setZone(path, zones, curX, curY - 1, 2)
+        setZone(path, zones, curX, curY + 1, 1)
+      }
+
+    // North-South
+    } else if (curTile == 10) {
+      // Going south
+      if (dy > 0) {
+        setZone(path, zones, curX+1, curY, 1)
+        setZone(path, zones, curX-1, curY, 2)
+
+      // Going north
+      } else {
+        setZone(path, zones, curX+1, curY, 2)
+        setZone(path, zones, curX-1, curY, 1)
+      }
+
+    // Corner
+    } else if (curTile != 15) {
+      val east: Boolean = (curTile & 1) != 0
+      val south: Boolean = (curTile & 2) != 0
+
+      val toEast: Boolean = dx > 0
+      val toSouth: Boolean = dy > 0
+
+      val offsetBottom: Boolean = east ^ toEast ^ toSouth
+      val zoneY: Boolean = !toSouth ^ east
+
+      val offsetRight: Boolean = south ^ toEast ^ toSouth
+      val zoneX: Boolean = toEast ^ south
+
+      val offsetY: Int = if (offsetBottom) 1 else -1
+      val zoneYVal: Int = if (zoneY) 2 else 1
+      setZone(path, zones, curX, curY+offsetY, zoneYVal)
+
+      val offsetX: Int = if (offsetRight) 1 else -1
+      val zoneXVal: Int = if (zoneX) 2 else 1
+      setZone(path, zones, curX+offsetX, curY, zoneXVal)
+    }
+  }
+
+  private def setZone(path: ArrayBuffer[(Int, Int)], zones: Array[Array[Int]], posX: Int, posY: Int, zone: Int): Unit = {
+    val height: Int = zones.length
+    val width: Int = if (height == 0) 0 else zones(0).length
+    if (0 <= posX && posX < width && 0 <= posY && posY < height) {
+      if (!path.contains((posX, posY))) {
+        zones(posY)(posX) = zone
+      }
+    }
+  }
+}

src/day10/Puzzle2.scala

@@ -0,0 +1,147 @@
+package day10
+
+import scala.collection.immutable.HashMap
+import scala.collection.mutable.ArrayBuffer
+import scala.io.{BufferedSource, Source}
+
+object Puzzle2 {
+  var grid: Array[Array[Byte]] = Array.empty
+  var zones: Array[Array[Int]] = Array.empty
+
+  // bits: NWSE
+  val TILES: Map[Char, Byte] = HashMap(
+    '|' -> 10,
+    '-' -> 5,
+    'L' -> 9,
+    'J' -> 12,
+    '7' -> 6,
+    'F' -> 3,
+    '.' -> 0,
+    'S' -> 15
+  )
+
+  var height: Int = 0
+  var width: Int = 0
+  var startX: Int = 0
+  var startY: Int = 0
+
+  def loadInput(path: String): Unit = {
+    val source: BufferedSource = Source.fromFile(path)
+    val lines: Array[String] = source.getLines().toArray
+
+    height = lines.length
+    width = if (height == 0) 0 else lines(0).length
+    grid = Array.ofDim(height, width)
+    zones = Array.ofDim(height, width)
+
+    for ((line: String, y: Int) <- lines.zipWithIndex) {
+      for ((c: Char, x: Int) <- line.zipWithIndex) {
+        grid(y)(x) = TILES(c)
+        if (c == 'S') {
+          startX = x
+          startY = y
+        }
+      }
+    }
+
+    source.close()
+  }
+
+  def calculateArea(): Int = {
+    val path: ArrayBuffer[(Int, Int)] = new ArrayBuffer()
+    path.addOne((startX, startY))
+
+    val walker: Walker = new Walker(startX, startY)
+
+    do {
+      walker.walk(grid)
+      path.addOne(walker.getPos())
+    } while (walker.getX() != startX || walker.getY() != startY)
+    println(s"Found path (length = ${path.length})")
+
+    val painter: Painter = new Painter(startX, startY, 2*startX-path(1)._1, 2*startY-path(1)._2)
+    do {
+      painter.walk(grid, zones, path)
+    } while (painter.getX() != startX || painter.getY() != startY)
+    println("Painted path neighbours")
+
+    var newZones: Array[Array[Int]] = Array.ofDim(height, width)
+    var filled: Boolean = false
+    var exteriorZone: Int = 0
+
+    do {
+      filled = true
+      newZones = copyZones()
+      for (y: Int <- 0 until height) {
+        for (x: Int <- 0 until width) {
+          if (zones(y)(x) == 0 && !path.contains((x, y))) {
+            filled = false
+            fillTile(x, y, newZones)
+          }
+        }
+      }
+      zones = newZones
+    } while (!filled)
+    println("Filled zones")
+
+    for (y: Int <- 0 until height) {
+      for (x: Int <- 0 until width) {
+        if (x == 0 || x == width - 1 || y == 0 || y == height - 1) {
+          if (zones(y)(x) != 0) {
+            exteriorZone = zones(y)(x)
+          }
+        }
+      }
+    }
+    println(s"Found exterior zone: $exteriorZone")
+
+    var area: Int = 0
+    for (y: Int <- 0 until height) {
+      for (x: Int <- 0 until width) {
+        if (zones(y)(x) != exteriorZone && zones(y)(x) != 0) area += 1
+      }
+    }
+    println(s"Calculated area: $area")
+
+    return area
+  }
+
+  def fillTile(x: Int, y: Int, newZones: Array[Array[Int]]): Unit = {
+    var zone: Int = 0
+
+    for ((dx: Int, dy: Int) <- Walker.OFFSETS) {
+      val x2: Int = x + dx
+      val y2: Int = y + dy
+      if (0 <= x2 && x2 < width && 0 <= y2 && y2 < height) {
+        if (zones(y2)(x2) != 0) {
+          zone = zones(y2)(x2)
+        }
+      }
+    }
+
+    newZones(y)(x) = zone
+  }
+
+  def copyZones(): Array[Array[Int]] = {
+    val result: Array[Array[Int]] = Array.ofDim(height, width)
+    for (y: Int <- 0 until height) {
+      for (x: Int <- 0 until width) {
+        result(y)(x) = zones(y)(x)
+      }
+    }
+    return result
+  }
+
+  def solve(path: String): Int = {
+    loadInput(path)
+
+    val solution: Int = calculateArea()
+
+    return solution
+  }
+
+  def main(args: Array[String]): Unit = {
+    val solution: Int = solve("./res/day10/input1.txt")
+    println(solution)
+  }
+}

src/day10/Walker.scala

@@ -1,15 +1,11 @@
 package day10
 
 class Walker {
-  private var x: Int = 0
-  private var y: Int = 0
-  private var lastX: Int = -1
-  private var lastY: Int = -1
-  private var distance: Int = 0
-
-  val OFFSETS: Array[(Int, Int)] = Array(
-    (1, 0), (0, 1), (-1, 0), (0, -1)
-  )
+  protected var x: Int = 0
+  protected var y: Int = 0
+  protected var lastX: Int = -1
+  protected var lastY: Int = -1
+  protected var distance: Int = 0
 
   def this(startX: Int, startY: Int) = {
     this()
@@ -41,7 +37,7 @@ class Walker {
 
   private def getNextPos(grid: Array[Array[Byte]], width: Int, height: Int): (Int, Int) = {
     val curTile: Byte = grid(y)(x)
-    for (((dx: Int, dy: Int), i: Int) <- OFFSETS.zipWithIndex) {
+    for (((dx: Int, dy: Int), i: Int) <- Walker.OFFSETS.zipWithIndex) {
       val x2: Int = x + dx
       val y2: Int = y + dy
       if (x2 != lastX || y2 != lastY) {
@@ -58,3 +54,9 @@ class Walker {
     throw new Exception("Dead-end path")
   }
 }
+
+object Walker {
+  val OFFSETS: Array[(Int, Int)] = Array(
+    (1, 0), (0, 1), (-1, 0), (0, -1)
+  )
+}