leetcode 235. Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”

Given binary search tree:  root = [6,2,8,0,4,7,9,null,null,3,5]

        _______6______
       /              \
    ___2__          ___8__
   /      \        /      \
   0      _4       7       9
         /  \
         3   5

Example 1:

2
8
6

Example 2:

2
4
2

?

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# Definition for a binary tree node. # class TreeNode(object): #     def __init__(self, x): #         self.val = x #         self.left = None #         self.right = None   class Solution(object):     def lowestCommonAncestor(self, root, p, q):         """         :type root: TreeNode         :type p: TreeNode         :type q: TreeNode         :rtype: TreeNode         """         node = root         while node:             if node.val in {p.val, q.val}:                 return node             elif node.val > p.val and node.val > q.val:                 node = node.left             elif node.val < p.val and node.val < q.val:                 node = node.right             else:                 return node