BST Insert - Scala DSA

Insert values into a binary search tree by comparing at each node.

Algorithm

The canonical tree is 4(2(1,3),6(5,7)), so this Scala DSA implementation can be compared directly with the rest of the DSA track.

Basic Implementation

basic.scala

import scala.collection.mutable.{ArrayBuffer, Queue}
class Node(val value: Int, var left: Node = null, var right: Node = null)
object Main {
  def render(node: Node): String = {
    if (node == null) "_"
    else if (node.left == null && node.right == null) node.value.toString
    else s"${node.value}(${render(node.left)},${render(node.right)})"
  }
  def sampleTree(): Node = new Node(4, new Node(2, new Node(1), new Node(3)), new Node(6, new Node(5), new Node(7)))
  def listString(values: Seq[Int]): String = values.mkString("[", ", ", "]")
  def insert(root: Node, value: Int): Node = { if (root == null) return new Node(value); if (value < root.value) root.left = insert(root.left, value) else root.right = insert(root.right, value); root }
  def main(args: Array[String]): Unit = { var root: Node = null; for (value <- List(4, 2, 6, 1, 3, 5, 7)) root = insert(root, value); println(render(root)) }
}

Complexity

Time: O(h) per insert
Space: O(n)

Implementation notes

Render tree structure explicitly instead of printing node objects.
The replay highlights the node, traversal state, queue, path, or search cursor that changes at each step.

binary search tree Values smaller than a node go left; larger values go right.