leetcode 235 - lowest common ancestor in bst.py

# lowest common ancestor in binary search tree | leetcode 235 | https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
# method: iteration through each node, when p and q are in different subtrees, current node is LCA

# Definition for a binary tree node.
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution:
    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
        cur = root
        
        while cur:
            if p.val > cur.val and q.val > cur.val:
                cur = cur.right
            elif p.val < cur.val and q.val < cur.val:
                cur = cur.left
            else:
                return cur

        return root