Find a Corresponding Node of a Binary Tree in a Clone of That Tree — Python

# Time:  O(n)
# Space: O(h)

import itertools


# Definition for a binary tree node.
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None


class Solution(object):
    def getTargetCopy(self, original, cloned, target):
        """
        :type original: TreeNode
        :type cloned: TreeNode
        :type target: TreeNode
        :rtype: TreeNode
        """
        def preorder_gen(node):
            stk = [node]
            while stk:
                node = stk.pop()
                if not node:
                    continue
                yield node
                stk.append(node.right)
                stk.append(node.left)
            
        for node1, node2 in itertools.izip(preorder_gen(original),
                                           preorder_gen(cloned)):
            if node1 == target:
                return node2