Very nice solution, but I don't understand how/why it works. Can someone explain?

edit: I understand it now: The solution is the same as

prodSansN ns = zipWith (*) (scanl (*) 1 ns) (tail $ scanr (*) 1 ns)

My main problem was a wrong understanding of what scanr does.

done

done

Random tests sometimes generate value for n for which no (nontrivial) solution exists

Very hard 3kyu (at least in Agda) but very nice!

This one is crazily cool and rewarding. It should be translated to Python by a someone.

Very technical kata.

done

Can't edit top post now, the structure guidelines are here: https://docs.codewars.com/authoring/guidelines/description#structure

• Sample tests noItemsJustMoreTimesDeclared and someNoValuesAsWellAsSomeHaveValuesAssigned are expecting incorrect results
• Please remove unexplained weird special cases like "empty data containers"
• Author's solution occasionally but reproducibly times out. The performance tests need to be more lenient.
• Please provide number of random tests and input size in kata description.
• Please use Markdown formatting and follow kata description [structure guideline]. The current conversational style has a lot of useful information but it's poorly formatted, completely mixed up, and mixed in with a lot of unnecessary words, so it's very difficult to refer to when coding.

Some possible improvements

• Better feedback in random tests: Consider adding a print every, say, 100 tests to let user know how much more to optimize.

More comments in spoilered comment below:

:) Well done!
So glad to see this, though it has been 4 years since then and I am no longer able to spare time to finish the authoring of this kata. But anyway this problem and the solutions to it has their own aesthetic value.