Why?

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why

soy retrasado

I guess it was all said but please find my below comments:
The description should mention about very large numbers involved as well as
possibility of empty strings.

Anyway - this is max Kata 6kyu.

Ok, I used another "for" loop instead of recursion and it works :) Yeahhhh!!
However there is still something I don't get with null return while using resursive call of method.
In VisualStudio all works but in Codewars editor there is some problem with return of null.

I assume it's from the introduction of Clang 8.

Right. Modified. Thanks!

The C-version issues a number of warnings from the testcase-code when doing the attempt. I assume it's from the introduction of Clang 8.

A great kata btw.

Thanks for reply and verification of my code. Sorting is not required - you can read on that in the author's comments in Discourse.
Duplicates are the problem in my code. I found the issue . I am working hard on loops modification.

I tried looking over the code, and one problem I noticed right away is that your list has a bunch of duplicates, and it's also not sorted (expected result is sorted list). With those problems fixed, here's what your code generates for pin "9173" in each iteration:

6,8,9
61,82,94
614,827,948
6142,8273,9486

As you can see, that is not correct. The 2nd row should be 61,62,64,81,82,84,91,92,94 (I think). It looks like you're missing one more loop somewhere.

Also, if you read error messages, they tell you what elements are expected, and which ones are missing.

BTW, recursion is definitely not needed, but it's possible both ways.

I guess I found the issue with my algorithm.
I need to use recursion instead of loops.

"There nust be something wrong with tests" is too vague and not a kata issue, rather a question. C# has 687 completions so far, and it's unlikely something is wrong (and you didn't bother to provide an example).

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