Binary Tree Inorder Traversal

leetcode第94题，二叉树中序遍历，但是要求不要使用递归，所以就是二叉树遍历的非递归形式，利用栈来做。

废话不说多，直接上代码吧。

# 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 inorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
currNode = root
ans = []
stack = []
while (currNode or len(stack)!=0 ):
while currNode:
stack.append(currNode)
currNode = currNode.left
currNode = stack[-1]
stack.pop()
ans.append(currNode.val)
currNode = currNode.right
return ans