aaaand now i'm super-glad i gave this one a pass.

...except you still have to get the name's length, which is O(n) as well.

Wow, guess I learned something new today! :D

You are probably right, and If I were to make the kata again I would probably do so, however I think changing it now would require quite some changes to the test code, and may invalidate a lot of solutions, so I think its better to leave it as it is.

The cards are then dealt out face up in three columns of 7 cards each.

the columns need to have 7 cards each

you goddamn right

Going by their profile, Python.

Stack of boxes, element of the 2D array.

    box = [[1, 3, 2],
           [4, 5, 1],
           [7, 2, 9]]

The two dimensions of the array represent the position of each stack in a plane. Each value represents the height of each stack or pile of boxes.
If you were to write that in a (x, y, z) format it would be like this:

(0,0,1), (1,0,3), (2,0,2), (0,1,4), (1,1,5), (2,1,1), (0,2,7), (1,2,2), (2,2,9)

What do you call stack? Actually I think it's really not clear what is 3D here. The matrices are effectively 2D ones (in the easy version, it's one-dimensional)f, it's just that we have to imagine that the matrix is moved in 3 dimensions when we compute the changes on it. However I don't think it's a big issue.

The value of each stack is the 3rd dimension.

Lenght, width and height are 3 dimensions.

Everything is consistent, on the contrary. Unless you did find badly set tests, but that's very unlikely, and however it's impossible to do anything since you no information at all, not even the language you're using.

I have the same problem... this task seems to me unclear because nothing works. I completed the easier one and I though this is in the same manner but it is senseless to guess what to do