Leetcode 94 Binary Tree Inorder Traversal

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

class Solution:
    # @param {TreeNode} root
    # @return {integer[]}
    def inorderTraversal(self, root):
        if root is None:  
            return []  
        elif root.left is None and root.right is None:  
            return [root.val]  
        else:  
            return self.inorderTraversal(root.left)+[root.val]+self.inorderTraversal(root.right)