Lots of OOP-concepts and data structures questions (i.e., difference between pass by value and pass by reference, what is the underlying structure of the Set abstraction in C++, what is the difference between lookup in a Vector and lookup in a Set, how would you pass an object by reference when you don't want it modified in the called function, advantages of linked lists, difference between vectors and linked lists, how you would insert a node in a doubly linked list). This was a phone interview. Lasted for about an hour, just a rapid-fire round of technical questions and questions about my past work. Interviewer was very nice and encouraging.