import scala.collection.mutable

import scala.collection.mutable.{HashMap, ArrayBuffer}

​

​

​

object Main {

​

  class TreeNode(var value: Int) {

    var children: ArrayBuffer[TreeNode] = new ArrayBuffer[TreeNode]()

  }

  def getDevices(root: TreeNode, server: TreeNode, ttl: Int): ArrayBuffer[Int] = {

    var neighbors = new HashMap[Int, ArrayBuffer[Int]] // Adjacency list

    dfs(null, root, neighbors)

​

    // BFS to find nodes

    var bfs = new ArrayBuffer[Int]

    bfs += server.value

    var lookup = new mutable.HashSet[Int]

    for(b <- bfs){

      lookup += b

    }

    var i = 0

    while(i<ttl){

      var temp = new ArrayBuffer[Int]

​

      for (node <- bfs) {

        for (nei <- neighbors(node)) {

          if (lookup.contains(nei) == false)

            temp += nei

        }

      }

      i += 1

      bfs = temp

      for(b <- bfs){

        lookup += b

      }

​

    }

    bfs

  }

​

  private def dfs(parent: TreeNode, child: TreeNode, neighbors: HashMap[Int, ArrayBuffer[Int]]): Unit = { // DFS to build adjacency list

​

    if (child == null) {

      return

    }

    if (parent != null) {

      if (!neighbors.contains(parent.value))

        neighbors.put(parent.value, new ArrayBuffer[Int])

      if (!neighbors.contains(child.value))

        neighbors.put(child.value, new ArrayBuffer[Int])

      neighbors(parent.value)+= child.value

      neighbors(child.value) += parent.value

    }

    for (i <- 0 until child.children.size) {

      dfs(child, child.children(i), neighbors)

​

    }

​

  }

​

  def main(args: Array[String]): Unit = { // Driver Code

    val root = new TreeNode(1)

    root.children += new TreeNode(2)

    root.children += new TreeNode(3)

    root.children += new TreeNode(4)

    root.children(0).children += new TreeNode(5)

    root.children(0).children(0).children += new TreeNode(10)

    root.children(0).children += new TreeNode(6)

    root.children(0).children(1).children += new TreeNode(11)

    root.children(0).children(1).children += new TreeNode(12)

    root.children(0).children(1).children += new TreeNode(13)

    root.children(2).children += new TreeNode(7)

    root.children(2).children += new TreeNode(8)

    root.children(2).children += new TreeNode(9)

    val server = root.children(0).children(1)

    val ttl = 2

    println("The TTL value will expire on node IDs: " + getDevices(root, server, ttl))

  }

}