implement day 12 part 1 in kotlin

day12/part1.kt

@@ -0,0 +1,87 @@
+import java.io.File
+import kotlin.collections.MutableList
+import kotlin.math.abs
+import kotlin.system.exitProcess
+import kotlin.text.Regex
+
+data class Vector(val x: Int, val y: Int, val z: Int) {
+    fun add(other: Vector): Vector {
+        return Vector(this.x + other.x, this.y + other.y, this.z + other.z)
+    }
+
+    fun value(): Int {
+        return abs(this.x) + abs(this.y) + abs(this.z)
+    }
+
+    override fun toString(): String {
+        return "Vector(x=${this.x}, y=${this.y}, z=${this.z})"
+    }
+}
+
+class Moon(val pos: Vector, val vel: Vector) {
+    override fun toString(): String {
+        return "Moon(pos=${this.pos}, vel=${this.vel})"
+    }
+
+    fun value(): Int {
+        return this.pos.value() * this.vel.value()
+    }
+
+    companion object {
+        val reg = Regex("<x=(-?[0-9]+), y=(-?[0-9]+), z=(-?[0-9]+)>")
+        fun parse(s: String): Moon {
+            val parsed = reg.matchEntire(s)!!
+            return Moon(
+                Vector(
+                    parsed.groupValues[1].toInt(),
+                    parsed.groupValues[2].toInt(),
+                    parsed.groupValues[3].toInt()
+                ),
+                Vector(0, 0, 0)
+            )
+        }
+    }
+}
+
+fun main(args: Array<String>) {
+    if (args.count() != 1) {
+        println("error: supply a filename!")
+        exitProcess(1)
+    }
+
+    var moons: MutableList<Moon> = ArrayList()
+    File(args[0]).forEachLine { moons.add(Moon.parse(it)) }
+
+    for (q in 0 until 1000) {
+        for ((i, moon) in moons.withIndex()) {
+            var (vX, vY, vZ) = moon.vel
+            for (o_moon in moons) {
+                if (o_moon == moon) {
+                    continue
+                }
+                if (o_moon.pos.x > moon.pos.x) {
+                    vX += 1
+                } else if (o_moon.pos.x < moon.pos.x) {
+                    vX -= 1
+                }
+                if (o_moon.pos.y > moon.pos.y) {
+                    vY += 1
+                } else if (o_moon.pos.y < moon.pos.y) {
+                    vY -= 1
+                }
+                if (o_moon.pos.z > moon.pos.z) {
+                    vZ += 1
+                } else if (o_moon.pos.z < moon.pos.z) {
+                    vZ -= 1
+                }
+            }
+            moons[i] = Moon(moon.pos, Vector(vX, vY, vZ))
+        }
+
+        for ((i, moon) in moons.withIndex()) {
+            moons[i] = Moon(moon.pos.add(moon.vel), moon.vel)
+        }
+    }
+
+    println(moons.map { it.value() }.sum())
+}