LeetCode: Trim A Binary Search Tree Solution

1/*
2Definition for a binary tree node.
3function TreeNode(val, left, right) {
4  this.val = (val===undefined ? 0 : val)
5  this.left = (left===undefined ? null : left)
6  this.right = (right===undefined ? null : right)
7}
8
9A BST is a BT which every node fit this ordering condition: all left descendents <= n < all right descendents
10*/
11
12var trimBST = function (root, low, high) {
13  if (!root) return root
14  if (root.val > high) return trimBST(root.left, low, high)
15  if (root.val < low) return trimBST(root.right, low, high)
16
17  root.left = trimBST(root.left, low, high)
18  root.right = trimBST(root.right, low, high)
19
20  return root
21}