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].

The idea is push to stack the element until you find the leftmost node, then pop stack, and do the same thing in the right sub tree.

//LMR
    public List<Integer> inorderTraversal(TreeNode root) {        
        //incoming node is root
        Stack<TreeNode> nodes = new Stack<TreeNode>();
        List<Integer> values = new ArrayList<Integer>();
        while (!nodes.isEmpty() || root!=null) {
            if (root != null) {
                nodes.push(root);
                root = root.left;
            } else {
                root = nodes.pop();
                values.add(root.val);
                root = root.right;
            }
        }     
        return values;
    }