work smarter not harder :P

That is some clever obfuscation. It turns out to be definitely in the 7 kyu neighborhood, after random tests timed out, and I was briefly tempted to use pthreads. whew!

Thanks natan, I will give that a try.

That's an interesting situation you found. It's a strange thing to be testing without any corresponding specification - it has purpose but I think the test output should be phrased differently because that's bit of a red herring. If you print out your parameters a b c that should tell you enough to continue.

i thought it needs algorithim binary tree or somesthing like that using recursion
but found that it need a better look numbers reltion to each other starting from n

Maybe I'm missing a nuance in what is expected, but the C++ test_tree_with_23_nodes test (and later) seem broken. Ex for test_tree_with_23_nodes test:
Expected: [ 12, 13, 16, 1, 40, 29, 2, 19, 6, 35, 3, 38, 6, 22, 29, 8, 10, 10, 8, 21, 1, 36, 33 ]
Actual: [ 22, 8, 35, 3, 13, 29, 38, 1, 6, 10, 19, 29, 33, 36, 40, 1, 2, 6, 8, 10, 12, 16, 21 ]

As you can see, the expected starts out incorrectly sorted after the first level

                                     12
                               *13*      16
                           ...

Thanks to you I discovered the feature Next

I guess the answer is yes, since I was able to solve it on this basis.

Funny kata to figure out.

Question about "a string representing a grid like in the above pictures".

Does this mean there will always be either 0 or 2 '-' between every pair of '+'?

they were?

Funny kata to learn some new concepts with.

You can skip door 8 and go directly to door 9. You end up paying 7 + 9 + 10 = 26.

I don't understand the underlying maths: e.g. if we start at 7, and the jewels are behind doors number 10, we haveto pay 7 + 8 + 9 + 10 = 34, however the description says it is 26. Where is 26 coming from?