230. Kth Smallest Element in a BST

题目:
https://leetcode.com/problems/kth-smallest-element-in-a-bst/

难度:
Medium

跟昨天做的一道题类似，一上来就走取巧之路。

InOrder排序，输出，当然也完全可以用昨天的binary tree iterator,入stack,出stack,知道输出第k位

class Solution(object):
    def kthSmallest(self, root, k):
        """
        :type root: TreeNode
        :type k: int
        :rtype: int
        """
        self.root = root
        self.lst = []
        self.inOrder(root)
        return self.lst[k-1]

    def inOrder(self, root):
        if root == None:
            return
        self.inOrder(root.left)
        self.lst.append(root.val)
        self.inOrder(root.right)