this image should really be in the description

technically, there is no proof given here of that most important last part that (n,k)%3==0 for k!=0,n and for n==3^d, though it is not hard to deduce, yet not that obvious.

Can you please explain why that's the case? I'm new to programming and just want to understand why that is.

great

just select the correct language version in the edit panel. If not available, that means you use stuff that is specific to the 2.7 version (like print 20, x)

you are right, instructions are very bad

Had the same issue fixed it by optimizing signum to do fewer computations.

I hated it 1st...then luv it :-)

Probably a mishap happened during one of the re-validation. I've now triggered re-validation so the solutions should pop up as valid again.

Still not clear.

The meaning of "on the top line" is the two subtrees where we only go left or only go right plus the root element.
You should probably also specify how the result should be ordered.

Only the ones that are you access going one way(either left or right)

I don't know Haskell so...