递归与二叉树_leetcode235

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


# 二叉搜索树的公共祖先一定在[p,q]之间
class Solution(object):
    def lowestCommonAncestor(self, root, p, q):
        """
        :type root: TreeNode
        :type p: TreeNode
        :type q: TreeNode
        :rtype: TreeNode
        """

        if not root:
            return root

        if p.val < root.val and q.val < root.val:
            return self.lowestCommonAncestor(root.left,p,q)
        if p.val > root.val and  q.val > root.val:
            return self.lowestCommonAncestor(root.right,p,q)
        return root