剑指offer-二叉搜索树的第k个结点之python实现

 

# -*- 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, root, k):
        if root == None or k == 0:
            return None
        self.helper(root, k)
        if len(self.res) < k:
            return None
        return self.res[k - 1]
    def helper(self,root,k):
        if len(self.res) == k:
            return
        if root == None:
            return
        
        self.helper(root.left,k)
        self.res.append(root)
        self.helper(root.right, k)
        
    def __init__(self):
        self.res = []