0701-insert-into-a-binary-search-tree.js

/**
 * 701. Insert into a Binary Search Tree
 * https://leetcode.com/problems/insert-into-a-binary-search-tree/
 * Difficulty: Medium
 *
 * You are given the root node of a binary search tree (BST) and a value
 * to insert into the tree. Return the root node of the BST after the
 * insertion. It is guaranteed that the new value does not exist in the
 * original BST.
 *
 * Notice that there may exist multiple valid ways for the insertion,
 * as long as the tree remains a BST after insertion. You can return
 * any of them.
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} val
 * @return {TreeNode}
 */
var insertIntoBST = function(root, val) {
  if (!root) {
    return new TreeNode(val);
  }

  if (val > root.val) {
    root.right = insertIntoBST(root.right, val);
  } else {
    root.left = insertIntoBST(root.left, val);
  }

  return root;
};