Thinking Outside The Box

After yesterday's post "You've Never Had An Interview Like This!", as promised I'm posting the answers to the Google interview questions. I think part of the weird question style is to throw the person off, but it's also to see if you can "think outside the box" and how creative you are. I've asked some odd interview questions (not as extreme as a few Google ones), but I do it just to see if someone can think fast on their feet. I want to hear an answer that isn't your standard run of the mill robotic response that most people give during interviews. I want to see how he/she does under pressure, when something out of the ordinary is throw at him/her, how well can he/she deal with the situation. I think that is also probably what Google is looking for.

If you got any of these questions right, pat yourself on the back because they weren't easy to answer. Keep in mind that although some of the questions do have a definite right or wrong answer, some of the other questions can be answered correctly in numerous ways. Consider yourself warned, you may feel like you are back in high school taking the SATs again.

1. Solve this cryptic equation, realizing of course that value for M and E could be interchanged. No leading zeros are allowed: WWWDOT - GOOGLE = DOTCOM

Answer: 777589 - 188106 = 589483 or 777589 - 188103 = 589486

2. How many different ways can you color an icosahedron with one of three colors on each face?

Answer: 58,130,055

3. Which of the following expresses Google's over-arching philosophy?

a) I'm feeling lucky
b) Don't be evil
c) Oh, I already fixed that
d) You should never be more than 50 feet from food
e) All of the above

Answer: b

4. You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving in 60 seconds. What do you do?

Answer: Take off all my clothes, wedge them between the blades and the floor to prevent it from turning. Back up against the edge of the blender until the electric motor overheats and burns out. Using the notches etched in the side for measuring, climb out. If there are no such notches or they're too far apart, retrieve clothes and make a rope to hurl myself out.

5. How would you find out if a machine's stack grows up or down in memory?

Answer: Instantiate a local variable. Call another function with a local. Look at the address of that function and then compare. If the function's local is higher, the stack grows away from address location 0. If the function's local is lower, the stack grows towards address location 0. If they're the same, you did something wrong!

6. Explain a database in three sentences to your eight-year-old nephew.

Answer: A database is a way of organizing information. It's like a genie who knows where every toy in your room is. Instead of hunting for certain toys yourself and searching the whole room, you can ask the genie to find all your toy soldiers, or only X-Men action figures, or only race cars - anything you want.

7. How many gas stations would you say there are in the United States?

Answer: A business doesn't stick around for long unless it makes a profit. Let's assume that all gas stations in the US are making at least some profit over the long run. Assume that the number of people who own more than 1 car is negligibly small relative to the total American population. Figure that 20% of people are too young to drive a car, another 10% can't drive because of disability or old age, 5% of people use public transportation or carpool, another 5% choose not to drive, and another 5% of the cars are inventory sitting in lots or warehouses that a dealership owns but which no one drives.

There's about 280 million people in the US. Subtracting 50%, that means there's about 140 million automobiles and 140 million drivers for them. The busiest city or interstate gas stations probably get a customer pulling in about twice a minute, or about 120 customers per hour. A slower gas station out in an agrarian area probably sees a customer once every 10 or 15 minutes, or about 4 customers per hour. Let's take a weighted average and suppose there's about 1 customer every 90 seconds, or about 40 customers an hour. Figuring a 14 hour business day (staying open from 7 AM to 9 PM), that's about 560 customers a day.

If the average gas station services 560 customers a day, then there are 250,000 gas stations in the US. This number slightly overstates the true number of gas stations because some people are serviced by more than 1 gas station. (Actual number in 2003, according to the Journal of Petroleum Marketing: 237,284, an error of about 5%.)