day 16 puzzle 1

README.md

@@ -5,11 +5,11 @@ This repo contains my attempt at this year's Advent of Code (2023)
 I will try and do some problems (probably not all of them) in Scala
 
 ## Progress:
-#### Stars: 28 / 50
+#### Stars: 29 / 50
 |        Mon         |        Tue        |        Wed         |        Thu         |        Fri         |        Sat        |        Sun         |
 |:------------------:|:-----------------:|:------------------:|:------------------:|:------------------:|:-----------------:|:------------------:|
 |                    |                   |                    |                    | 1<br>:star::star:  | 2<br>:star::star: | 3<br>:star::star:  |
 | 4<br>:star::star:  | 5<br>:star::star: | 6<br>:star::star:  | 7<br>:star::star:  | 8<br>:star::star:  | 9<br>:star::star: | 10<br>:star::star: |
-| 11<br>:star::star: |        12         | 13<br>:star::star: | 14<br>:star::star: | 15<br>:star::star: |        16         |         17         |
+| 11<br>:star::star: |        12         | 13<br>:star::star: | 14<br>:star::star: | 15<br>:star::star: |   16<br>:star:    |         17         |
 |         18         |        19         |         20         |         21         |         22         |        23         |         24         |
 |         25         |                   |                    |                    |                    |                   |                    |

src/day16/Mirrors.scala

@@ -0,0 +1,10 @@
+package day16
+
+object Mirrors extends Enumeration {
+  type Mirror = Value
+  val NONE = Value(".")
+  val DIAGONAL_TL_BR = Value("\\")
+  val DIAGONAL_BL_TR = Value("/")
+  val SPLITTER_HOR = Value("-")
+  val SPLITTER_VER = Value("|")
+}

src/day16/Puzzle1.scala

@@ -0,0 +1,103 @@
+package day16
+
+import day16.Mirrors.{DIAGONAL_BL_TR, DIAGONAL_TL_BR, Mirror, NONE, SPLITTER_HOR, SPLITTER_VER}
+
+import scala.collection.mutable.ArrayBuffer
+import scala.io.{BufferedSource, Source}
+
+object Puzzle1 {
+  var mirrors: Array[Array[Mirror]] = Array.empty
+  var energized: Array[Array[Boolean]] = Array.empty
+  var width: Int = 0
+  var height: Int = 0
+  val OFFSETS: Array[(Int, Int)] = Array(
+    (1, 0), (0, 1), (-1, 0), (0, -1)
+  )
+  val path: ArrayBuffer[(Int, Int, Int)] = new ArrayBuffer()
+
+  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
+    mirrors = Array.ofDim(height, width)
+    energized = Array.ofDim(height, width)
+
+    for ((line: String, y: Int) <- lines.zipWithIndex) {
+      for ((c: Char, x: Int) <- line.zipWithIndex) {
+        val mirror: Mirror = Mirrors.withName(""+c)
+        mirrors(y)(x) = mirror
+      }
+    }
+
+    source.close()
+  }
+
+  def shootBeam(startX: Int, startY: Int, startDir: Int): Unit = {
+    if (startX < 0 || startX >= width || startY < 0 || startY >= height) return
+    var x: Int = startX
+    var y: Int = startY
+    var dir: Int = startDir
+    var continue: Boolean = true
+    do {
+      if (path.contains((x, y, dir))) return
+      path.addOne((x, y, dir))
+
+      energized(y)(x) = true
+
+      mirrors(y)(x) match {
+        case NONE => {}
+        case DIAGONAL_TL_BR => {
+          dir = Math.floorDiv(dir, 2)*2 + 1 - (dir % 2)
+        }
+        case DIAGONAL_BL_TR => {
+          dir = 3 - dir
+        }
+        case SPLITTER_HOR => {
+          if (dir % 2 == 1) {
+            continue = false
+            shootBeam(x+1, y, 0)
+            shootBeam(x-1, y, 2)
+          }
+        }
+        case SPLITTER_VER => {
+          if (dir % 2 == 0) {
+            continue = false
+            shootBeam(x, y+1, 1)
+            shootBeam(x, y-1, 3)
+          }
+        }
+      }
+
+      if (continue) {
+        val offset: (Int, Int) = OFFSETS(dir)
+        x += offset._1
+        y += offset._2
+      }
+
+      if (x < 0 || x >= width) continue = false
+      if (y < 0 || y >= height) continue = false
+    } while (continue)
+  }
+
+  def solve(path: String): Int = {
+    loadInput(path)
+    shootBeam(0, 0, 0)
+
+    var solution: Int = 0
+
+    for (y: Int <- 0 until height) {
+      for (x: Int <- 0 until width) {
+        if (energized(y)(x)) solution += 1
+      }
+    }
+
+    return solution
+  }
+
+  def main(args: Array[String]): Unit = {
+    val solution: Int = solve("./res/day16/input1.txt")
+    println(solution)
+  }
+}

tests/day16/Puzzle1Test.scala

@@ -0,0 +1,9 @@
+package day16
+
+import org.scalatest.funsuite.AnyFunSuite
+
+class Puzzle1Test extends AnyFunSuite {
+  test("Puzzle1.solve") {
+    assert(Puzzle1.solve("tests_res/day16/input1.txt") == 46)
+  }
+}

tests_res/day16/input1.txt

@@ -0,0 +1,10 @@
+.|...\....
+|.-.\.....
+.....|-...
+........|.
+..........
+.........\
+..../.\\..
+.-.-/..|..
+.|....-|.\
+..//.|....