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What is the standard balanced binary search tree implementation one should use in Scala 2.10.x? I am looking around and it seems that AVLTree was removed and RedBlack is deprecated with a message (Since version 2.10.0) use TreeMap or TreeSet instead. However, TreeMap and TreeSet do not provide the functionality I need because I need to be able to traverse the tree and build a more complex data structure based on this.

Is there any new class that provides the plain balanced binary tree functionality that is not deprecated?

jbx
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  • Are you looking for a mutable or immutable structure? – 0__ Feb 24 '14 at 22:09
  • Well anything that works well at this point... immutable would be nice – jbx Feb 25 '14 at 00:31
  • Why aren't you able to traverse? – Edmondo1984 Jul 31 '14 at 11:20
  • Scala TreeMap and TreeSets are implemented using a red-black tree source code of which is available at https://github.com/scala/scala/blob/2.11.x/src/library/scala/collection/immutable/RedBlackTree.scala. –  May 07 '15 at 08:31

2 Answers2

5

Trees are fundamental to functional programming and scala, and depending on the complexity of your requirement it wouldn't be a bad idea to roll your own BTree with whatever linkage type and traversal methods fit.

As a general model it could look something like this:

trait BSTree[+A] {
  def value: Option[A] = this match {
    case n: Node[A] => Some(n.v)
    case l: Leaf[A] => Some(l.v)
    case Empty      => None
  }

  def left: Option[BSTree[A]] = this match {
    case n: Node[A] => Some(n.l)
    case l: Leaf[A] => None
    case Empty      => None
  }

  def right: Option[BSTree[A]] = this match {
    case n: Node[A] => Some(n.r)
    case l: Leaf[A] => None
    case Empty      => None
  }
}

case class Node[A](v: A, l: BSTree[A], r: BSTree[A]) extends BSTree[A]
case class Leaf[A](v: A) extends BSTree[A]
case object Empty extends BSTree[Nothing]
Alex Ehrnschwender
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1

You can try this home-made version of binary search trees:

https://github.com/melvic-ybanez/scala-bst

As far as I'm concerned, I am using HashSet which sort the data by key very efficiently when they are immutable.

Mikaël Mayer
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