Welcom! Glad it played out well.

Hello @yuryk, @JohanWilthnik and @Bling4Basics!
Many thanks to all of you for your time dedicated for helping me!
I have found the reason of my problem - it is bug in my code.
Sorry for taking your time - i should have been more attentive being solving this problem myself.
And thanks again to all!

Yuri, thank you for your suggestions. You were completely right. There are bug in my solution which causes infinite loop on particular tests. Discovering this fact took so much time just because i had used console printing not thoroughly enough for the first time:-)

@curiouscoder, for some solutions, the time may vary strongly when different clues are provided. Maybe in the 'secret' tests there is a sequence of clues that causes an infinite loop or just takes a long time. Also, if you run the 'Attempt Solution' multiple times - are the resulting times the same?

Yep, I suspected that it might be considered a spoiler. I'd suggest you use some console printing and output the solving times yourself for comparison.

Sorry, Yuri, but someone has desided that your comment contains spoiler, and i hasn't read it :-(
I smell a conspiracy here :-)

Hello, Yuri!
Could it be possible, that for final qualification (attemt) somehow server dedicates less resources than for sample tests running?
I just can't find reasonal explanation to the fact, that my code easily passes same set of tests as on final qualification but only in "sample tests" environment...

We have a different C# complaint.

Could you see if his problem is reproducible? It might also be a platform issue, I have no way to tell.

Sorry, only see this now.

Leave it as is, for the foreseeable future.

ATM we only have two solutions anyway (one of which is yours). When people start complaining it's too easy, it'll be early enough to upgrade it.

I'd like to disagree with you on the importance, &c.

If about half the solvers complain they had to do real work optimising their previous solution then the kata hit the mark I intended to set. But the kata should be solvable. Otherwise, (a) it'll never get out of beta (what rating it gets is then up to the community, but it's been set now and translations should reasonably comply with that) and (b) it only leads to frustration with solvers. Neither seems to me to be the intention of this platform.

@psv, thank you for the explanation and for the C translation! It was the only language i could solve it in and to add a translation myself, which i really wanted to do.
Forgive me for not asking you directly about the test: i was too carried away with my own translation that just did not think. I'd like to disagree about the importance of a stable benchmark in random tests. Shouldn't it be like: 'Bring it on (as long as it's valid input)!' And if the solution has a sensitivity for input - great, that's where it surfaces.

Thank you, again

Please, correct me if i'm wrong: the C random tests always use the first test case only.

In the cpp random tests i made it test all 7 test cases.

Hope it's al'right.

These 7 test cases have different levels of complexity so a time consumption of different tests varies widely (depends on an algorithm).

In C translation is used only one test case as the basis of random tests to obtain a more stable total time consumption. This is important for 10 random tests.

Of course, for a large number of tests, the total time consumption doesn't depend on the level of complexity of individual tests.