LeetCode(96)Binary Tree Inorder Traversal

题目如下:

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?

题目分析:

二叉树的常规题目包括进行树的前序，中序，后序，层序遍历。使用对于其中的前3个，可以使用递归和非递归两种方式。本题是进行中序遍历，鼓励使用非递归。之前也写过类似的文章。所以直接贴出提交到leetcode的代码如下。

//8ms过大集合
/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode *root) {
        vector<int> res_vec;
        if(root==NULL)
            return res_vec;
        TreeNode* cur_node=root;
        std::stack<TreeNode*> stack_left;
        while(cur_node!=NULL){
            stack_left.push(cur_node);
            cur_node=cur_node->left;
        }
        while(!stack_left.empty()){
            cur_node=stack_left.top();
            res_vec.push_back(cur_node->val);
            cur_node=cur_node->right;
            stack_left.pop();
            while (cur_node!=NULL) {
                stack_left.push(cur_node);
                cur_node=cur_node->left;
            }
        }
        return res_vec;
    }
};