The interview process was very normal, with two phone screens followed by onsite interviews.

While I've interviewed at many companies before, this was the only one where I had a really negative experience. The interviewer showed up late and was uninterested throughout the entire process.

This was also the first time I was rejected after answering all questions correctly. I'm really not sure what their hiring criteria are.

Generate all subsets of a string.

This involves finding all possible combinations of characters within a given string, including the empty string.