剑指offer-二叉搜索树的第k个结点树-python

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回对应节点TreeNode
    def KthNode(self, pRoot, k):
        # write code here
        if not pRoot or not k :
            return 
        res = []
        def midTraversal(node):
            if len(res)>=k or not node :
                return
            midTraversal(node.left)
            res.append(node)
            midTraversal(node.right)
        midTraversal(pRoot)
        if len(res)<k:
            return 
        return res[k-1]