I've been thinking about it too

you used an extra variable r in your code for the same purpose, only it was a pointer instead of an index

Why do you need 'k' when you have 'count'?

Fixed.

The outputs for "expected" and "but was" are apparently swapped in the Java version, which is a bit confusing.

The kata was approved overnight when I do not have an access to my laptop.

However, I would like to ask you, what do you mean by in C, the "value = 2" in description is never used? The original task was made in Python and the author of the C translation did not change the description, stating that the description to the katas should be language-agnostic.

About the definition of what "trace" is, I agree. By marking this task as "beginner-friendly", I should have stated the key things.

The one-liner code and the full description was written by me, only the idea of the task has been taken from the test makers. I missed that part in ToU, so thank you for pointing that out.

TIL on Wikipedia:

the trace of a square matrix A, denoted tr(A), is the sum of the elements on its main diagonal, a[1][1] + a[2][2] + ⋯ + a[n][n]. It is only defined for a square matrix (n × n).

Indeed, it would be good to add this term & link to the description, as so many other katas also do.

Instructions could be improved. For example in C, the "value = 2" in description is never used. And later examples don't all state the values; nor do they define what a "trace" is.

indeed, iBits+2 instead of n+2... but i dunno why i even did a malloc instead of just a fixed sizeof(int)*8+2 byte array or something...

Resu can become unnecessarily huge for large values of n.

I guess great minds think similarlly ;).

That's really clever, but it's undefined C (that is, side-effect operations with binary operations yield undefined effects). And the strict defintion of "undefined behavior" means allowing the compiler to do anything it chooses.

cuz it looks beautiful!

looks elegant but inefficient indeed.