Lowest Common Ancestor of a Binary Search Tree

package tree.recursive;

import tree.TreeNode;

public class LowestCommonAncestorOfABinarySearchTree {

    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode a, TreeNode b) {
        return helper(root, Math.min(a.val, b.val) , Math.max(a.val, b.val));
    }

    private TreeNode helper(TreeNode root, int low, int high) {
        if (root == null || root.val == low || root.val == high) return root;
        if (low < root.val && root.val < high)                   return root;
        return helper(root.val > high ? root.left : root.right, low, high);
    }

}

package com.eureka
package tree.recursive

import tree.TreeNode

import scala.annotation.tailrec

object LowestCommonAncestorOfABinarySearchTree:

  def lowestCommonAncestor(_root: TreeNode, p: TreeNode, q: TreeNode): TreeNode =

    @tailrec def go(root: TreeNode, min: Int, max: Int): TreeNode =
      if root == null || root.value == min || root.value == max then root
      else if min < root.value && root.value < max then root
      else go(if root.value > max then root.left else root.right, min, max)

    go(_root, math.min(p.value, q.value), math.max(p.value, q.value))