剑指Offer62：二叉搜索树的第k个结点

思路：

# -*- 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):#取第k个
        # write code here
        global result
        result=[]
        self.midnode(pRoot)
        if  k<=0 or len(result)<k:
            return None
        else:
            return result[k-1]
              
    def midnode(self,root):#中序遍历
        if not root:
            return None
        self.midnode(root.left)
        result.append(root)
        self.midnode(root.right)