this site is about challenging yourself to new puzzles and problems. do not be afraid that if a question you use appears here then it won't be worth asking anymore. first, people who come to this site to read the problems are the type of people you want to hire. they are the people who get excited about solving problems, and actively search out new problems to ask themselves.

second, if you ask someone a question that they already know the answer to, then ask them to solve it again. if the question is such an "aha!" question that knowing the answer takes all the fun out of the question, then don't ask it. it won't tell you a single thing about the interview candidate besides whether they already know the answer to the question.

examples of these sorts of questions are: "100 people died in a plane crash on the border between usa and canada. where did they bury the survivors?" or "you have 3 switches and 3 lightbulbs in separate rooms. you are allowed to play with the switches and then go into the room with the bulbs only once (i.e. you can't go back and play with the switches again). how can you tell which switch goes to which bulb?"

the first question is just a trick. the second one is an "aha!" some people may say the second one requires "thinking outside the box" but i say "phooey!" its no good for an interview. you want to ask questions that have a process to them, so even if the candidate knows the answer, they still have to explain the process or algorithm to you to demonstrate they understand it. programming questions, math questions, and puzzles are the best option.

i post links to solutions usually a month after the problem is posted, sometimes earlier, sometimes later. check the discussion board to see if someone has already posted an answer (usually if someone posts a good solution which is well worded, i will just use that as the posted solution)

btw, my name is michael pryor. i graduated from dartmouth in '98 and now i work at fogcreek software. if you interview here, you may hear these questions, but most likely you'll get even harder ones.

link: dr. dobb's journal programming questions
link: chris sells microsoft interview questions
link: ace the interview: similar site to this one
link: car talk puzzles

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