# 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]

        """

        res=[]

        stk=[]

        if root == None:

            return res

        while root != None or len(stk) != 0:

            if root != None:

                stk.append(root)

                root=root.left

            elif len(stk) != 0:

                tmpNode=stk.pop()

                res.append(tmpNode.val)

                root=tmpNode.right

        return res