7 ms·

It's been a long time since my interview (2005), but I had a couple of brain teasers during my my interview. Not as many as I had at Microsoft, but definitely s

It's been a long time since my interview (2005), but I had a couple of brain teasers during my my interview. Not as many as I had at Microsoft, but definitely some. I specifically remember being asked the Two Eggs question (http://www.datagenetics.com/blog/july22012/ http://www.datagenetics.com/blog/july22012/).

jmillikin 13y ago
The two eggs question seems fair to ask an engineer. It's an optimization problem, and could just as easily be rephrased in real world terms (e.g. branching in a hard-realtime microcontroller). The solution can be arrived at through math and reasoning. Typically, trick questions are things like "how many golf balls fit in a bus", "you've been shrunk and dropped in a blender" , or the infamous "why are manhole covers round". These supposedly test the candidate's creativity, but actually just test whether the candidate has read a book of riddles recently.
- sbisker 13y ago
  Google definitely asked me "how many ping pong balls fit in an airplane" straight up back in 2007. Then again I like Fermi problems. :)
- sanderjd 13y ago
  Man, I don't necessarily think they should be used in technical interviews, but I really don't get the aversion to these kinds of questions - stuff like this is so much fun to think about and debate! I personally think manhole covers should be human-cross-section-from-above-shaped.
- jrockway 13y ago
  I disagree with your categorization of "how many golf balls fit in a bus" as a trick question. That's a normal estimation problem that's highly relevant to a software engineer's daily work. (Rephrase the question as "how many users can you serve with one CPU core". Capacity planning is an entire department's worth of work.)
  - philwelch 13y ago
    Please tell me you guys do capacity planning with more than just vague numbers you pull out of your ass, a whiteboard, and some guy staring at you making subjective judgments of the number you come up with.
    - tomkarlo 13y ago
      Yes, but we don't expect someone to use actual numbers in response to a hypothetical question in an interview. The question is intended to see if you could figure out which numbers you'd really need to figure out the right estimate. Often, the specific result of an estimate is less interesting than the user's understanding of what drives that estimate, because it determines if they understand the levers they can pull to change the outcome in the real world.
      - philwelch 13y ago
        Sure, if you ask the actual question about capacity planning. The golf balls and bus question gets you where exactly?
        jrockway 13y ago
        Abstraction. I hear computer programming is pretty abstract.
        philwelch 13y ago
        Well that was a little condescending. If you think it's vitally important to screen people for their ability to solve Fermi problems, it's no skin off my back. I was just trying to have a conversation.
        tomkarlo 13y ago
        You don't want to ask the actual question about the specific application, because it gives a strong advantage to a candidate who has worked on that very specific situation in the past (and they may be able to sneak through just by regurgitating from memory.) It's better to have a scenario they're unlikely to have seen previously. As an interviewer, I'm not interested in your ability to remember solutions you received from others, I want to know how you deal with a problem you haven't seen before. Sometimes folks call these "puzzlers" but I think they're unfairly lumped in with true "puzzlers" - crap like "why is a manhole round" where there's a right answer that depends on either experience or some specific insight. A question where you're asking a candidate to walk through their thought process on a hypothetical (but reasonable) situation isn't "puzzling" unless you just can't handle the question.
enjo 13y ago
I had a couple as well, back in '08 or so.

jmillikin 13y ago

The two eggs question seems fair to ask an engineer. It's an optimization problem, and could just as easily be rephrased in real world terms (e.g. branching in a hard-realtime microcontroller). The solution can be arrived at through math and reasoning. Typically, trick questions are things like "how many golf balls fit in a bus", "you've been shrunk and dropped in a blender" , or the infamous "why are manhole covers round". These supposedly test the candidate's creativity, but actually just test whether the candidate has read a book of riddles recently.

sbisker 13y ago
Google definitely asked me "how many ping pong balls fit in an airplane" straight up back in 2007. Then again I like Fermi problems. :)
sanderjd 13y ago
Man, I don't necessarily think they should be used in technical interviews, but I really don't get the aversion to these kinds of questions - stuff like this is so much fun to think about and debate! I personally think manhole covers should be human-cross-section-from-above-shaped.
jrockway 13y ago
I disagree with your categorization of "how many golf balls fit in a bus" as a trick question. That's a normal estimation problem that's highly relevant to a software engineer's daily work. (Rephrase the question as "how many users can you serve with one CPU core". Capacity planning is an entire department's worth of work.)
- philwelch 13y ago
  Please tell me you guys do capacity planning with more than just vague numbers you pull out of your ass, a whiteboard, and some guy staring at you making subjective judgments of the number you come up with.
  - tomkarlo 13y ago
    Yes, but we don't expect someone to use actual numbers in response to a hypothetical question in an interview. The question is intended to see if you could figure out which numbers you'd really need to figure out the right estimate. Often, the specific result of an estimate is less interesting than the user's understanding of what drives that estimate, because it determines if they understand the levers they can pull to change the outcome in the real world.
    - philwelch 13y ago
      Sure, if you ask the actual question about capacity planning. The golf balls and bus question gets you where exactly?
      - jrockway 13y ago
        Abstraction. I hear computer programming is pretty abstract.
        philwelch 13y ago
        Well that was a little condescending. If you think it's vitally important to screen people for their ability to solve Fermi problems, it's no skin off my back. I was just trying to have a conversation.
      - tomkarlo 13y ago
        You don't want to ask the actual question about the specific application, because it gives a strong advantage to a candidate who has worked on that very specific situation in the past (and they may be able to sneak through just by regurgitating from memory.) It's better to have a scenario they're unlikely to have seen previously. As an interviewer, I'm not interested in your ability to remember solutions you received from others, I want to know how you deal with a problem you haven't seen before. Sometimes folks call these "puzzlers" but I think they're unfairly lumped in with true "puzzlers" - crap like "why is a manhole round" where there's a right answer that depends on either experience or some specific insight. A question where you're asking a candidate to walk through their thought process on a hypothetical (but reasonable) situation isn't "puzzling" unless you just can't handle the question.

enjo 13y ago

I had a couple as well, back in '08 or so.