At my company we don't bother with specific problems. When we ask a candidate: "If you were asked to build x program how would you go about it", the answer we are looking for is along these lines: "I would go online and find someone who has already done the problem and replicate/alter it to fit my needs". The majority of the questions we ask are like: "Where do you see yourself in 5 years.", "What does our company do?", "Present us with a time when you had to overcome a challenge and failed.". If your going to work with someone then its best you know that they are capable of learning. After all, a degree isn't about proving you know something, it's about proving you have the ability to learn and fight for that knowledge when necessary. It proves you have drive and direction in your life; important qualities in a candidate.