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2019/Scala/day12/Day12.scala

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+package day12
+
+class Day12 {
+
+  def step(array: Array[Moon], n: Int): Unit = {
+    for (_ <- 0 until n) {
+      for (i <- array.indices; j <- array.indices) {
+        array(i).changeVelBy(array(j))
+      }
+      for (i <- array.indices) {
+        array(i).physStep()
+      }
+    }
+  }
+
+  def print(array: Array[Moon]): Unit = {
+    for (i <- array.indices) {
+      array(i).print()
+    }
+  }
+
+  def solveP1(): Int = {
+    val array: Array[Moon] = Array(new Moon(-16, 15, -9), new Moon(-14, 5, 4), new Moon(2, 0, 6), new Moon(-3, 18, 9))
+
+    step(array, 1000)
+    array.foldLeft (0) {(a, x) => a + x.energy}
+  }
+
+
+  def solveP2(): Long = {
+    val array1: Array[Moon] = Array(new Moon(-16, 15, -9), new Moon(-14, 5, 4), new Moon(2, 0, 6), new Moon(-3, 18, 9))
+    val array2: Array[Moon] = Array(new Moon(-16, 15, -9), new Moon(-14, 5, 4), new Moon(2, 0, 6), new Moon(-3, 18, 9))
+    val array3: Array[Moon] = Array(new Moon(-16, 15, -9), new Moon(-14, 5, 4), new Moon(2, 0, 6), new Moon(-3, 18, 9))
+
+    @scala.annotation.tailrec
+    def findFirstXRepeat(array: Array[Moon], n: Int = 1): Int = {
+      step(array, 1)
+      if (array(0).posX == -16 && array(1).posX == -14 && array(2).posX == 2 && array(3).posX == -3) n+1
+      else findFirstXRepeat(array, n+1)
+    }
+
+    @scala.annotation.tailrec
+    def findFirstYRepeat(array: Array[Moon], n: Int = 1): Int = {
+      step(array, 1)
+      if (array(0).posY == 15 && array(1).posY == 5 && array(2).posY == 0 && array(3).posY == 18) n+1
+      else findFirstYRepeat(array, n+1)
+    }
+
+    @scala.annotation.tailrec
+    def findFirstZRepeat(array: Array[Moon], n: Int = 1): Int = {
+      step(array, 1)
+      if (array(0).posZ == -9 && array(1).posZ == 4 && array(2).posZ == 6 && array(3).posZ == 9) n+1
+      else findFirstZRepeat(array, n+1)
+    }
+
+    @scala.annotation.tailrec
+    def GCD(a: Long, b: Long): Long = if (b == 0) a.abs else GCD(b, a % b)
+
+    def LCM(a: Long, b: Long): Long = (a * b).abs / GCD(a, b)
+
+    val repX = findFirstXRepeat(array1)
+    val repY = findFirstYRepeat(array2)
+    val repZ = findFirstZRepeat(array3)
+
+    LCM(repZ, LCM(repX, repY))
+  }
+
+}

2019/Scala/day12/Main.scala

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+package day12
+
+import kamlib.{Reader, Wrapper}
+
+object Main {
+
+  def main(args: Array[String]): Unit = {
+    val solution: Day12 = new Day12()
+
+    println("Part 1:")
+    Wrapper(solution.solveP1()).print()
+    println("Part 2:")
+    Wrapper(solution.solveP2()).print()
+
+  }
+}

2019/Scala/day12/Moon.scala

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+package day12
+
+class Moon(var x: Int, var y: Int, var z: Int) {
+  var vx = 0
+  var vy = 0
+  var vz = 0
+
+  def changeVelBy(other: Moon): Unit = {
+    if (other.x < x) vx -= 1
+    else if (other.x > x) vx += 1
+    if (other.y < y) vy -= 1
+    else if (other.y > y) vy += 1
+    if (other.z < z) vz -= 1
+    else if (other.z > z) vz += 1
+  }
+
+  def physStep(): Unit = {
+    x += vx
+    y += vy
+    z += vz
+  }
+
+  def print(): Unit = println(s"pos=<x=$x, y=  $y, z= $z>, vel=<x= $vx, y= $vy, z= $vz>")
+
+  def energy: Int = {
+    val potential = x.abs + y.abs + z.abs
+    val kinetic = vx.abs + vy.abs + vz.abs
+    potential * kinetic
+  }
+
+  def kinetic: Int = vx.abs + vy.abs + vz.abs
+
+  def posX: Int = x
+  def posY: Int = y
+  def posZ: Int = z
+}