题解 | #二叉搜索树的第k个结点#

知识点：对二叉搜索树进行中序遍历，可以得到一组升序数组。 解题思路：利用dfs中序递归二叉搜索树，输出数组中第k个结点。

# -*- 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 __init__(self):
        self.count=0
    def KthNode(self, pRoot, k):
        # write code here
        if not pRoot or not k:return None
        res=[]
        def in_order(cur):
            if not cur: return
            in_order(cur.left)
            self.count+=1
            res.append(cur)
            in_order(cur.right)
        in_order(pRoot)
        if self.count<k:return None
        return res[k-1]