Leetcode: Binary Tree Inorder Traversal

http://oj.leetcode.com/problems/binary-tree-inorder-traversal/

/**
 * 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;
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        stack<TreeNode*> myStack;
        TreeNode* current = root;
        while(current!=NULL) {
            myStack.push(current);
            current=current->left;
        }
        while(myStack.empty()==false){
            current = myStack.top();
            myStack.pop();
            res.push_back(current->val);
            current=current->right;
            while(current!=NULL) {
                myStack.push(current);
                current=current->left;
            }
        }
        return res;
    }
};