LeetCode Binary Tree Inorder Traversal

1.题目

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?

2.解决方案1

class Solution {  
public:  
    vector<int> inorderTraversal(TreeNode *root) {  
        vector<int> path;  
        stack<TreeNode *> st;