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Technical Interview Questions

So you’re nearing the end of what is probably the most stressful pop-quiz of your life: the technical interview. But you’re doing great though! You knew what a quaternion was and you totally nailed that pinned-beam question — pun intended!

And then suddenly, a lob. The interviewer leans forward and takes a short sip from his Dilbert mug. “Tell me, if the time is 3:15, what is the angle between the hands on the clock?”

Is this a joke, you think. This is an engineering position, isn’t it? Is he checking to see if I’m awake? You quickly visualize the clock.

“Zero”, you respond confidently. The interviewer grins. “Hmmm… good.” An awkward silence fills the room. Somewhere off in the distance, a dog barks.

Weeks go by, and you don’t get a callback.

Lying awake at night, mulling over the interview, you glance at your Street Fighter II analog wall clock. Through steel blue glow of your charging cell-phone, you see Ryu staring back at you behind the ticking hands. It’s 3:15. And the hands are 7.5 degrees apart. Not zero.

Interviewers ask these riddles to see if you can quickly demonstrate reasoning. Can you in fact visualize the problem at hand and effortlessly know how to approach it? You’d better.

So while knowledge of engineering fundamentals and the relevant requirements are important, your ability to quickly and correctly reason may set you apart from other candidates.

The following, along with “3:15″, are some actual interview questions I’ve heard. There are also some classics that should be slam dunks, including one really good question from “Boy Meets World”.

So get yourself a piece of paper, a pen, and minimize Google you cheater.

How many piano tuners are there in New York City?

How many gas stations are there in LA?

You have two jars, 50 red marbles and 50 blue marbles. A jar will be picked at random, and then a marble will be picked from the jar. Placing all of the marbles in the jars, how can you maximize the chances of a red marble being picked? What are the exact odds of getting a red marble using your scheme?

Write a program to determine triangle type (right, isosceles, etc), given three side lengths.

You are in an empty room and you have a transparent glass of water. The glass is a right cylinder, and it looks like it’s half full, but you’re not sure. How can you accurately figure out whether the glass is half full, more than half full, or less than half full?

If Bill can paint a fence in 30 minutes, and Bob can paint a fence in 20 minutes, how long will it take if they work together?

If you had a 5 quart and 3 quart bucket and an infinite supply of water, how would you measure out exactly 4 quarts?

And finally, here’s one from my personal stash:

How do cemeteries stay in business?

[Thanks to Sellbrothers for some of these! Great list!]