I had the same issue but I changed sizeof(arr) to arr.size() and it worked.

Does not work for second unit test.

There also may be hidden requirements such as they pass in a different data/var type and it could through off the code. For instances like this if you truly believe its an error you can raise an issue in the kata and see if it gets fixed, otherwise it may be an edge case.

You can either print the output of the function/variables/etc. and run the tests or use/create your own tests in the bottom right window, that allows for you to do test driven development and work out different edge cases while you attempt to solve the kata.

smart to just add the letter tather than putting it in an else statement!

even i have a habit of using re for substitution, its better when you want to substitute symbols, numbers or any other criteria

Submitting parameters for a function required for this regarding bases should not return passing tests for function(A, B) as well as funciton (B,A); this should be reviewed and the tests adjusted.