Could someone please explain what does next smallest mean? Thanks!!
In the test case, it has input: {1,#,2}. My output is [1], but it's expecting [1,2]

I also has the same confusion. If the iterator is initialized to root node, then next smallest element should be the the smallest element of its right child.
For example, if given {1,#, 2}, then the next smallest element should be 2, correct?