You should add random tests.

Translated to C++

Please review and approve.

Good point, will add that.

My mistake - after re-reading the description I see how the result follows given the ordering.

Found this link which might be worthwhile to add to the discussion to help people "visualize" what to do:
http://randscullard.com/CircleOfFifths/

Translated to c++

As it stands, out of bounds values in arr2 should be ignored while retaining the valid elements.
For anything other than int's in arr2 the function should return empty.
Will update the discussion and tests to reflect this.

It's implicit in the description but will add it in writing.

Hi,

If an element of arr2 is out of bounds for arr1 then it should be ignored.
However the other elements of arr2 should still be used.

Hope this helps.

Good point.

I think the function should ignore indices which are out of bounds but.
For invalid input the function should just return [].

Thanks for the suggestions, will add it to the description.

Thanks for the suggestions, will incorporate them.

I feel it's a bit vague if you don't know about the circle of fifths
and key signatures...