aoc/2018/day8/part1.scala

import scala.io.StdIn.readLine

case class Node(c: Char, nbChild: Int, nbMetadata: Int, children: List[Node], metadata: List[Int])

val it = readLine.split(" ").map(_.toInt).toList

def readNode(c: Char, input: List[Int]): (Int, Node) = input match {
  case nbChild :: nbMeta :: t =>
    val (read, children) = List.range(0, nbChild, 1).foldLeft((0, List.empty[Node])) { case (acc, id) =>
      val (read, node) = readNode((c + id + 1).toChar, t.drop(acc._1))
      (acc._1 + read, node :: acc._2)
    }
    val metadata: List[Int] = input.drop(read + 2).take(nbMeta).toList
  (read + 2 + nbMeta, Node(c, nbChild, nbMeta, children, metadata))
  case _ => (0, null)
}

val rootNode = readNode('A', it)._2

def sumMetadata(node: Node): Int = {
  val childrenSum = node.children.map(sumMetadata).sum
  val metadataSum = node.metadata.sum
//  println(s"Node ${node.c} children sum = $childrenSum, metadataSum = $metadataSum, both = ${childrenSum + metadataSum}")
  childrenSum + metadataSum          
}

// println(rootNode)

println(sumMetadata(rootNode))