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]

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Started by kSquared February 08, 2005 05:19 PM

79 comments, last by way2lazy2care 13 years, 9 months ago

kSquared

Author

1,356

February 09, 2005 04:17 PM

Quote:
Original post by Sagar_Indurkhya
2) What is the most beautiful equation you have ever seen? Explain.

Most beautiful equation? My hat's going in the ring for general relativity:

G_μν = 8π · GT_μν

- 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 04:28 PM

Quote:
Original post by furby100
Quote:
Original post by Sagar_Indurkhya
2) What is the most beautiful equation you have ever seen? Explain.

x=2. This equation is satisfied by 2. It follows that there are numbers that satisfy the equation x = 2. From that, it follows that there are numbers. From this simple equation one can settle one of the deepest philosophical questions about mathematics. Certainly a beautiful result.

However, it's almost certain most people will put e^ip + 1 = 0

never seen that one. What is it?

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kSquared

Author

1,356

February 09, 2005 04:29 PM

Quote:
Original post by Sagar_Indurkhya
Quote:
Original post by furby100
However, it's almost certain most people will put e^ip + 1 = 0

never seen that one. What is it?

Euler's identity. It unites five of the fundamental mathematical constants: zero, one, e, pi, and i. It's the case x = pi for the more general equation e^(ix) = cos(x) + i*sin(x).

JexMX

206

February 09, 2005 05:29 PM

What came first, the chicken or the egg?

Samith

2,465

February 09, 2005 05:50 PM

Quote:
Original post by JexMX
What came first, the chicken or the egg?

The egg, of course. The first bird genetically close enough to today's chicken to be considered a chicken was a chicken for its entire life (as in, it didn't suddenly turn into a chicken halfway through its life). That means it was born from an egg, a chicken egg.

Stonicus

157

February 10, 2005 05:04 PM

I'd say the chicken. If a non-chicken lays an egg, it's not a chicken egg. What came out was a chicken, but it wasn't supposed to be, so it wasn't a chicken egg, it was a mutated relative-of-chicken egg... So the first chicken egg had to come from a chicken, but the first chicken can come from a mutated Dodo egg.

Cold_Steel

835

February 10, 2005 05:30 PM

Quote:
Original post by Stonicus
I'd say the chicken. If a non-chicken lays an egg, it's not a chicken egg. What came out was a chicken, but it wasn't supposed to be, so it wasn't a chicken egg, it was a mutated relative-of-chicken egg... So the first chicken egg had to come from a chicken, but the first chicken can come from a mutated Dodo egg.

So, you say that the egg type is defined by what pooped out the egg, and not what's in the egg. Still, the question is whether the egg preceded the chicken. I don't think it matters what type of egg, just that there was indeed an egg directly related to the first chicken, that indeed preceded it.

I say egg came first.

______________________________"Man is born free, and everywhere he is in chains" - J.J. Rousseau

doogle

475

February 10, 2005 05:40 PM

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

Funny Google Response

hahahahaha

vrok137

241

March 28, 2011 04:46 PM

A while back I myself had a series of phone interviews with Google, the following were a few of the questions they asked, and we were allowed to ask questions as well:

There exists a file directory containing at least 55 thousand plaintext documents. Some of those documents contain phone numbers that are out of date. Given a list of invalid phone numbers and their new, updated equivalents, how would you go about updating all invalid phone numbers within all files within the directory?
Write an algorithm that performs a binary search on a sorted, but rotated array of integers.
Compare and contrast various data structures utilized across multiple programming languages: Hashtable, Hashmap, Treemap, etc.
Fun, Fun .

Google Interview Questions

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Google Interview Questions

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