Tough Questions From Google Job Interviews

There are many stories about job interviews at Google. But the most interesting part of any story is the list of questions:

Zach had a phone interview in October 2005 and he was asked things like:

"Google gets queries from around the world. Write a function that will return a two character string representing a country code given an IP address as its input."

Here is the answer:

"Essentially, you have to create a tree structure with the country codes as the leaves at the very bottom. I chose to split the IP addresses by octets. So the top level would contain all of the starting and ending numbers corresponding to the first octet on the IP address. So this tree structure would be very wide but only 4 levels deep."

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Pete Abilla was a little luckier and knew how to answer this question:
"You are at a party with a friend and 10 people are present including you and the friend. Your friend makes you a wager that for every person you find that has the same birthday as you, you get $1; for every person he finds that does not have the same birthday as you, he gets $2. Would you accept the wager?"

"The answer has to do with the number of days in the year and the probability the person’s birthday falls on the same day as mine (without replacement). I eventually solved it, but it took time learning how to apply probability with no replacement."

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An interesting problem from Google's aptitude test:
Given a triangle ABC, how would you use only a compass and straight edge to find a point P such that triangles ABP, ACP, and BCP have equal perimeters? (Assume that ABC is constructed so that a solution does exist.)

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The moderator of gamedev.net had a phone interview with rather odd questions:

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

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

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?

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Niniane Wang, who works at Google, has some tips for a job interview:

# Practice using the same medium (e.g. paper and pencil) and time limits (e.g. 30 minutes) as the real interview.
# During the interview, don't obsess over little mistakes that happen.
# Don't be rude to your interviewer.
# Don't hijack the interview (if you really want to talk about a project, ask your interviewer).
# When answering questions expecting a specific answer, give a high-level summary first.

So if you want to work at Google, get ready and good luck!