Intel Corporation interview questions

The interview with Intel was the most rigorous interview I have been through. After submitting a written application the process began. It started with 2 phone interviews, the first one about my prior experience contracting with Intel, the second one consisting of more technical questions. The face to face interviews were conducted one after the other, with 6 different people. These meetings were held in small cubicles in the cafeteria. Each face to face lasted about 30 minutes. The questions ranged over many topics. Several of the questions were logic puzzles, such as "Why is a manhole cover round?" and "You are in a room with 3 switches. Each switch is connected to a lightbulb located in a different room. When you leave the room with the switches the door will lock behind you. How can you set each switch so that you can tell which switch is connected to which lightbulb?" Other questions were technical, and still others were about my past work experiences. I was made an offer within a few days of the interview. After accepting the offer I had to report to a medical center for a urine analysis drug screening.