GUNWO

sealed trait BT[+A]
case object Empty extends BT[Nothing]
case class Node[+A](value:A, left:BT[A], right:BT[A]) extends BT[A]


sealed trait Graph[A]
case class GNode[A](value:A, list:List[Graph[A]]) extends Graph[A]

def graphToBT[A](graph: Graph[A]) = {
  def aux(graph1: Graph[A], acc: List[Graph[A]]): Node[A] = {
    graph1 match {
      case GNode(a, Nil) => if(acc.length == 0){
        return Node(a, Empty, Empty)}
      else {
        return Node(a, aux(acc.head, acc.tail), Empty)
      }
      case GNode(a, h::t) =>
        t match {
          case Nil => Node(a, aux(h, acc), Empty)
          case h2::t2 => Node(a, aux(h, (acc ++ t2)), aux(h2, List()))
        }
    }
  }
  aux(graph, List())
}

def graph1 = GNode(1, List(GNode(2, List(GNode(3, List(GNode(4, List(GNode(5, List())))))))))
def graph2 = GNode(1, List(GNode(2, List(GNode(3, List(GNode(4, List(GNode(5, List()), GNode(6, List()), GNode(7, List() )) )))))))
def graph3 = GNode(1, List(GNode(2, List(GNode(3, List(GNode(4, List(GNode(5, List()), GNode(6, List()), GNode(7, List() ), GNode(8, List() ), GNode(9, List() ), GNode(10, List() )) )))))))
graphToBT(graph1)
graphToBT(graph2)
graphToBT(graph3)