BreadthFirstSearch.scala

// https://www.hackerrank.com/challenges/bfsshortreach/problem


  def height(neighbors: Map[Int, Set[Int]], level: Int, stack: Set[Int], rst: Map[Int, Int]): Map[Int, Int] =
    if (stack.isEmpty) rst
    else {
      val known = stack.filterNot(rst.contains).map((_ -> level)).toMap ++ rst
      val set   = stack.flatMap(neighbors.get).flatten.filterNot(known.contains)
      height(neighbors, level + 1, set, known)
    }

  def bfs(n: Int, m: Int, edges: Array[Array[Int]], s: Int): Array[Int] = {
    val neighbors = edges.foldLeft(Map.empty[Int, Set[Int]]) { case (m, Array(from, to)) =>
      m.updatedWith(from)(_.map(_ + to).orElse(Some(Set(to)))).updatedWith(to)(_.map(_ + from).orElse(Some(Set(from))))
    }
    val map = height(neighbors, 1, neighbors.getOrElse(s, Set()), Map.empty)
    (1 to n).filterNot(_ == s).map(x => map.get(x).map(_ * 6).getOrElse(-1)).toArray
  }