Leetcode: Binary Tree Inorder Traversal

Question

Given a binary tree, return the inorder traversal of its nodes′ values.

For example:
Given binary tree {1,#,2,3},
1
\
2
/
3
return [1,3,2].

Note: Recursive solution is trivial, could you do it iteratively?

confused what “{1,#,2,3}” means? > read more on how binary tree is serialized on OJ.

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Analysis

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Solution

# Definition for a binary tree node.# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution:    # @param {TreeNode} root    # @return {integer[]}    def inorderTraversal(self, root):        return self.helper(root)    def helper(self,root):        if root==None:            return []        return self.helper(root.left) + [root.val] + self.helper(root.right)