#     def __init__(self, x):

#         self.val = x

#         self.left = None

#         self.right = None

class Solution:

    def inorderTraversal(self, root: TreeNode) -> List[int]:

        result = []

        def inorder(tree, result):

            if tree != None:

                if tree.left != None:

                    inorder(tree.left, result)

                result.append(tree.val)

                if tree.right != None:

                    inorder(tree.right, result)

        inorder(root, result)

        return result