235_lowest_common_ancestor_of_a_binary_search_tree.py

# 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
        """
        if not root or not p or not q:
            return None
        elif max(p.val, q.val) < root.val:
            return self.lowestCommonAncestor(root.left, p, q)
        elif min(p.val, q.val) > root.val:
            return self.lowestCommonAncestor(root.right, p, q)
        else:
            return root


if __name__ == "__main__":
    s = Solution()