Google Interview Questions

kSquared · 2011-05-19T23:10:14

[edit]: If you're coming here from digg, I've posted a comment in the comments section to clarify a few points. Also, note that this thread is over a year old! I had a phone interview with Google today. I took notes; some of the questions they asked were interesting. We were allowed to ask questions. The interviewer didn't ask many questions in response to my answers, except to occasionally say "interesting". There's almost certainly more than one answer to each of these, and a few are probably wrong answers or could be improved in some way; I only include my answers for comparison. Any intermediate questions that I asked for clarification or otherwise have been omitted. Without further ado, a few of the more interesting ones: Q: "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?" (my 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. Q: "How would you find out if a machine's stack grows up or down in memory?" (my 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!) Q: "Explain a database in three sentences to your eight-year-old nephew." (my 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. Q: "How many gas stations would you say there are in the United States?" (my 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 one 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 one customer every 90 seconds, or about 40 customers an hour. Figuring a fourteen-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 one gas station. [Actual number in 2003, according to the Journal of Petroleum Marketing: 237,284, an error of about 5%.] P.S. Apparently, if you make it to the next stage, you can't even tell people you're interviewing, because you sign a 6-page NDA. I haven't had to sign anything yet, though. edit: Obvious spelling mistake. tall --> tell. [Edited by - kSquared on March 5, 2006 11:48:43 PM]

Nice Coder

366

February 09, 2005 02:20 AM

Push a value into a stack, and subtract the stack pointers current value from the stack pointers value before you pushed the value.

If it is positive then the stack is going up, otherwise it is going down.

You then pop it back again (to return the stack to its origional state)

Also, for the blener one, i would go something like:
Resonate the glass until it shatters, then run away real fast.

For "how many gas stations in the us"? I would say, "Google it".

From,
Nice coder

Click here to patch the mozilla IDN exploit, or click Here then type in Network.enableidn and set its value to false. Restart the browser for the patches to work.

Raduprv

997

February 09, 2005 02:38 AM

Ironically, google doesn't know the answer to "how many gas stations in the us" (I just tried).

Eternal Lands (free, Open Source MMORPG)

Nemesis2k2

1,045

February 09, 2005 02:39 AM

Quote: Q: "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?"

Panic, because the rest of the ingredients are probably coming in a few seconds.

Quote: Q: "How would you find out if a machine's stack grows up or down in memory?"

Give it appropriate amounts of sunlight and water, and record observations over time.

Quote: Q: "Explain a database in three sentences to your eight-year-old nephew."

Well, basically it's a.... Wait a minute, who are you? I don't have an eight year old nephew.

Quote: Q: "How many gas stations would you say there are in the United States?"

I don't know, but when I see him next, I'll ask.

benryves

2,001

February 09, 2005 02:41 AM

Quote: Original post by Coaster Kev
Why not ask Google ... err... yeah

Funny Google Response

Why do Google want to shrink my donkey?

[Website] [+++ Divide By Cucumber Error. Please Reinstall Universe And Reboot +++]

shmoove

822

February 09, 2005 06:07 AM

Quote: Original post by benryves
Quote: Original post by Coaster Kev
Why not ask Google ... err... yeah

Funny Google Response

Why do Google want to shrink my donkey?

Yeah, your donkey, right....

They just want you to get in shape, that's all.

shmoove

kSquared

Author

1,356

February 09, 2005 08:21 AM

Quote: Original post by golopart
LOL. You don't need to do any of that. Make a function. If the function has the C calling convention then parameters on the right of the prototype will be pushed on first. Compare the address of two parameters. If the lefter parameter has a smaller address then the stack grows from high to low memory. Adjust according to calling convention. Newbies.

I would fire you just for using the word "lefter" alone. =P

- k2 "Choose a job you love, and you'll never have to work a day in your life." — Confucius"Logic will get you from A to B. Imagination will get you everywhere." — Albert Einstein"Money is the most egalitarian force in society. It confers power on whoever holds it." — Roger Starr{General Programming Forum FAQ} | {Blog/Journal} | {[email=kkaitan at gmail dot com]e-mail me[/email]} | {excellent webhosting}

Conner McCloud

1,135

February 09, 2005 08:32 AM

Quote:
Q: "How would you find out if a machine's stack grows up or down in memory?"

The correct answer is "Check the documentation."

Who's more valuable: The guy who can come up with some hack to calculate the value, or the guy who knows where to look up the value?

CM

kSquared

Author

1,356

February 09, 2005 08:35 AM

Quote: Original post by Conner McCloud
Quote:
Q: "How would you find out if a machine's stack grows up or down in memory?"

The correct answer is "Check the documentation."

From earlier:

Quote: Any intermediate questions that I asked for clarification or otherwise have been omitted.

I asked about that ("Is there a handy reference manual available somewhere?", and the response was "Your co-worker has a wobbly desk and is using it to prop it up right now." Heh, heh. At least Google has a sense of humor.

- k2 "Choose a job you love, and you'll never have to work a day in your life." — Confucius"Logic will get you from A to B. Imagination will get you everywhere." — Albert Einstein"Money is the most egalitarian force in society. It confers power on whoever holds it." — Roger Starr{General Programming Forum FAQ} | {Blog/Journal} | {[email=kkaitan at gmail dot com]e-mail me[/email]} | {excellent webhosting}

Sagar_Indurkhya

253

February 09, 2005 08:47 AM

My Comp Sci teacher once passed around this little application for google. It had some wierd stuff, though it makes it all the more interesting to work there:

1) Calculate the Resistance in ohm's that a knights move would require on an infinite plane of resistors(forgot the resistance of each resistor, or whatever).

2) What is the most beautiful equation you have ever seen? Explain.

3) You have 10,000 Apache servers, and 1 day to generate $1,000,000. What do you do?

And some other stuff.

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