LeetCode-Binary Tree Inorder Traversal

LeetCode-Binary Tree Inorder Traversal

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.

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List inorderTraversal(TreeNode root) {
        List result=new ArrayList();
        Stack stack=new Stack();
        TreeNode node=root;
        do {
            while(node!=null) {
                stack.push(node);
                node=node.left;
            }
        
            if(!stack.isEmpty()) {
                node=stack.pop();
                result.add(node.val);
                node=node.right;
            } 
        }while(!stack.isEmpty() || node!=null);
        
        return result;
    }
}