1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<int> inorderTraversal(TreeNode *root) {
13         vector<int> res;
14         if(root==NULL) return res;
15         stack<TreeNode*> s;
16         TreeNode* cur=root;
17         while(cur||!s.empty()){
18             while(cur!=NULL){
19                 s.push(cur);
20                 cur=cur->left;
21             }
22             cur=s.top();
23             s.pop();
24             res.push_back(cur->val);
25             cur=cur->right;
26         }
27         return res;
28     }
29     
30 };