National Stock Exchange interview questions

Applied to job posting, and then emailed asking to schedule a half hour in person interview. Once I arrived I told them a little bit about myself running through my resume and then it was straight to a white board. They asked about reversing a string in place, hash tables, finding the middle of a linked list, and mergesort. Want to emphasize that unlike a lot of places I've interviewed at they were all very nice and easy to talk to which I think is rare.