Reversing a string was initially a good interview question because in C you can keep probing multiple levels of knowledge with it. You learn if the interviewee

Reversing a string was initially a good interview question because in C you can keep probing multiple levels of knowledge with it. You learn if the interviewee knows the algorithm, then if they understand how to do it in place with a pointer, then if they understand the XOR pointer trick. It's not a very interesting problem in a language like Ruby or Python.