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I'm so, so tired of doing interviews filled with "did you memorize this particular algorithm" whiteboard coding questions. Especially given I'm not some fresh-o

I'm so, so tired of doing interviews filled with "did you memorize this particular algorithm" whiteboard coding questions. Especially given I'm not some fresh-out-of-college hire. The industry's research on this is pretty unequivocal that it's a terrible way to evaluate candidates for anything other than "isn't a complete idiot" which would also be accomplished by more reasonable questions. Why can't the industry finally just drop stupid whiteboard coding and move on to more practically focused questions?

UncleMeat 9y ago
Can you give an example of a good practically focused question?
- sushisource 9y ago
  I personally think the more design focused ones are good. EX: "Here's a system were building. How would you build it?" Then you build on that with "Ah, I see you want to use a cache between these two servers/regions, what kind of cache would it be, what are some limitations there, etc?" Or something like in the article where you start with a little code, and build on it to solve some problem that isn't a totally arbitrary tree traversal like most of the whiteboarding stuff seems to be.
  - ng12 9y ago
    See, I hate questions like that. They're completely face-level and easy to bullshit. I don't want to work at a company full of bullshitters.
  - pkaye 9y ago
    I do the design focus based on the candidates own background... something they have worked on in their resume. This also help me confirm they didn't make things up on their resume. For the coding part, I try to pick things that don't depend on someone hearing about it previously. I try to solve the problem myself in 1/3 the time I allot to the candidate since they are under pressure. Most candidates seem to struggle with simple problem though. A simple one I have asked in C is to reverse the order of numbers in an array in place.
    - billhathaway 9y ago
      If you are trying a new coding or design question, have a few co-workers try it first to help flesh out the wording and get data points on how long it takes to solve.
    - 0xfeba 9y ago
      > A simple one I have asked in C is to reverse the order of numbers in an array in place. Hm... int a[] = {1,2,3,4,5}; So, some kind of swap? for (x = 0, y = 4; x < 5; x++, y--) { a[x] ^= a[y]; a[y] ^= a[x]; a[x] ^= a[y]; } See, I wouldn't mind that on a whiteboard. I had similar question for a startup, and passed easily (I think!). But then the last question I got was 'find all word substrings in a string'. I struggled, giving a brute force answer (for each position in the string, check against dictionary and expand by one character until the end of the string), but struggled to improve on it. I didn't know about tries at the time, but even still it would be difficult for me to even try to code this on a whiteboard. Turns out it was "Google" question that was for optimizing runtime, and I cannot analyze like that on a whiteboard, unless it's obvious (nested for loops, etc.). Anyway, after struggling and giving up with that question the next guy came in and berated me and my current employer (defense contractor). Not sure if it was because they thought I wasted their time or what. I left after that--not someone I would want to work for.
      - allenlavoie 9y ago
        It's a nice xor swap, but I think you reversed your list twice. And xor swapping with x=y=2 is likely not ideal. Seems like exactly what I'd do in an interview too :p
        CodesInChaos 9y ago
        The xor swap failure when working on the same variable has been nicely exploited in the underhanded C contest: http://www.underhanded-c.org/_page_id_16.html http://www.underhanded-c.org/_page_id_16.html > The XOR-swap trick is an example of coders being too clever for their own good. Here, it gradually poisons the RC4 permutation with zeroes, until eventually the plaintext is just passed along in the clear.
  - UncleMeat 9y ago
    Isn't this just as bad as the "if you've seen this before" whiteboard questions? A lot of specific problem domains don't make for good general purpose questions. If I used my daily work as an interview question I'd insta-fail the large majority of candidates because they don't have relevant PhDs. There are good balances. The question I ask is a real problem for a real product but quickly reduces to something small and manageable rather than getting bogged down in incredibly specific requirements.
- viewtransform 9y ago
  At my Google screening interview, I was asked "How would you teach recursion to a 7 year old child ?" Apparently, the correct answer was Romanesco broccoli. I failed the interview and briefly sank into a depression questioning everything I knew about raising young children, self-similarity and recursion.
  - abhirag 9y ago
    Well clearly the answer was, "By teaching him recursion at age 6 and passing the age incremented by 1 as an argument because what kind of monster would let kids play with mutable state" :D
  - coupdejarnac 9y ago
    Interesting, I AM teaching 7 year olds about recursion, but I doubt any of them have seen Romanesco broccoli. Anyway, the example I use to demonstrate the fibonacci sequence is sunflower seeds. I hope you got another job that you enjoy.
  - shard 9y ago
    How about that old joke: "Pete and Repeat sat in a boat. Pete fell out, who's left?" Whether or not it works for the interview, it definitely works at annoying 7-year-olds.
opportune 9y ago
Honestly I find most white board coding questions to not veer into the "you'll only get this if you've seen it before" territory. Not to say that it can't happen, but in some of my interviews recently, I got the following whiteboard problems (all asking for optimal solutions): Find the largest palindrome substring of a string Shortest path solver (Djikstra's) Compute a power if the base is any double and the exponent is an integer Take an unsorted list and put all the odd numbers on one side, all the evens on the other Given an array/list of numbers that first increases then decreases and a number, determine if that number is in the array/list. Out of those five, only one requires you to have something somewhat memorized (path-finding), but even that is pretty basic, and I think they would have accepted non-optimal solutions that worked anyway, so really all you needed to know how to do was write a BFS that maintains the cost of the shortest-yet found path to each expanded vertex. The rest I think anybody - given enough time - could solve if they were a good programmer. Of course sometimes there are problems where you don't figure it out in time, and definitely (a minority of) problems that are too hard for a whiteboard interview, but you're not going to get every technical question right anyway. It increases the stochasticity of interviewing when you can fail the technical challenges of interviews for jobs you, on another interviewing day/with another set of question, would otherwise qualify for, but this is logical from a hiring perspective. It costs less to interview 20 people and accept one qualified candidate than to interview 5 people and accept an unqualified candidate. It's not that you need to know how to solve these problems to be a good programmer, or even that being able to solve these problems is indicative of a good programmer, it's that a bullshitter/unqualified candidate will fail these every time, while at least a few qualified candidates won't fail.
- Franciscouzo 9y ago
  Finding the optimal longest palindrome substring algorithm surely is in the "you'll only get this if you've seen it before" territory. Implementing a binary search algorithm is anything but trivial, you've got overflows, off-by-one errors, passing arguments by value, etc. Sure, the idea of finding the point in the array that starts decreasing with a binary search is simple, but the subtle ways you can write it wrong are practically infinite.
  - 9y ago
muzani 9y ago
They're sort of like how the military would judge physical fitness by the number of push ups one can do. It correlates with skill in general, but it biases towards people who practice it.
- arca_vorago 9y ago
  Which is sorta the point of the pft.
sjellis 9y ago
> Why can't the industry finally just drop stupid whiteboard coding and move on to more practically focused questions? Cynically, I wonder if it's sometimes because it's a crutch for the interviewers. Like anything else, interviewing is a skill that you learn through interest, study and practice. I've been carrying out technical interviews for years, and still wouldn't say that I get it right every time. If the interviewers have not made an effort to learn how to do interviews, or don't really want to do them, or don't actually know what the job will involve, then they can just fall back on asking algorithm questions.

UncleMeat 9y ago

Can you give an example of a good practically focused question?

sushisource 9y ago
I personally think the more design focused ones are good. EX: "Here's a system were building. How would you build it?" Then you build on that with "Ah, I see you want to use a cache between these two servers/regions, what kind of cache would it be, what are some limitations there, etc?" Or something like in the article where you start with a little code, and build on it to solve some problem that isn't a totally arbitrary tree traversal like most of the whiteboarding stuff seems to be.
- ng12 9y ago
  See, I hate questions like that. They're completely face-level and easy to bullshit. I don't want to work at a company full of bullshitters.
- pkaye 9y ago
  I do the design focus based on the candidates own background... something they have worked on in their resume. This also help me confirm they didn't make things up on their resume. For the coding part, I try to pick things that don't depend on someone hearing about it previously. I try to solve the problem myself in 1/3 the time I allot to the candidate since they are under pressure. Most candidates seem to struggle with simple problem though. A simple one I have asked in C is to reverse the order of numbers in an array in place.
  - billhathaway 9y ago
    If you are trying a new coding or design question, have a few co-workers try it first to help flesh out the wording and get data points on how long it takes to solve.
  - 0xfeba 9y ago
    > A simple one I have asked in C is to reverse the order of numbers in an array in place. Hm... int a[] = {1,2,3,4,5}; So, some kind of swap? for (x = 0, y = 4; x < 5; x++, y--) { a[x] ^= a[y]; a[y] ^= a[x]; a[x] ^= a[y]; } See, I wouldn't mind that on a whiteboard. I had similar question for a startup, and passed easily (I think!). But then the last question I got was 'find all word substrings in a string'. I struggled, giving a brute force answer (for each position in the string, check against dictionary and expand by one character until the end of the string), but struggled to improve on it. I didn't know about tries at the time, but even still it would be difficult for me to even try to code this on a whiteboard. Turns out it was "Google" question that was for optimizing runtime, and I cannot analyze like that on a whiteboard, unless it's obvious (nested for loops, etc.). Anyway, after struggling and giving up with that question the next guy came in and berated me and my current employer (defense contractor). Not sure if it was because they thought I wasted their time or what. I left after that--not someone I would want to work for.
    - allenlavoie 9y ago
      It's a nice xor swap, but I think you reversed your list twice. And xor swapping with x=y=2 is likely not ideal. Seems like exactly what I'd do in an interview too :p
      - CodesInChaos 9y ago
        The xor swap failure when working on the same variable has been nicely exploited in the underhanded C contest: http://www.underhanded-c.org/_page_id_16.html http://www.underhanded-c.org/_page_id_16.html > The XOR-swap trick is an example of coders being too clever for their own good. Here, it gradually poisons the RC4 permutation with zeroes, until eventually the plaintext is just passed along in the clear.
- UncleMeat 9y ago
  Isn't this just as bad as the "if you've seen this before" whiteboard questions? A lot of specific problem domains don't make for good general purpose questions. If I used my daily work as an interview question I'd insta-fail the large majority of candidates because they don't have relevant PhDs. There are good balances. The question I ask is a real problem for a real product but quickly reduces to something small and manageable rather than getting bogged down in incredibly specific requirements.
viewtransform 9y ago
At my Google screening interview, I was asked "How would you teach recursion to a 7 year old child ?" Apparently, the correct answer was Romanesco broccoli. I failed the interview and briefly sank into a depression questioning everything I knew about raising young children, self-similarity and recursion.
- abhirag 9y ago
  Well clearly the answer was, "By teaching him recursion at age 6 and passing the age incremented by 1 as an argument because what kind of monster would let kids play with mutable state" :D
- coupdejarnac 9y ago
  Interesting, I AM teaching 7 year olds about recursion, but I doubt any of them have seen Romanesco broccoli. Anyway, the example I use to demonstrate the fibonacci sequence is sunflower seeds. I hope you got another job that you enjoy.
- shard 9y ago
  How about that old joke: "Pete and Repeat sat in a boat. Pete fell out, who's left?" Whether or not it works for the interview, it definitely works at annoying 7-year-olds.

opportune 9y ago

Honestly I find most white board coding questions to not veer into the "you'll only get this if you've seen it before" territory. Not to say that it can't happen, but in some of my interviews recently, I got the following whiteboard problems (all asking for optimal solutions): Find the largest palindrome substring of a string Shortest path solver (Djikstra's) Compute a power if the base is any double and the exponent is an integer Take an unsorted list and put all the odd numbers on one side, all the evens on the other Given an array/list of numbers that first increases then decreases and a number, determine if that number is in the array/list. Out of those five, only one requires you to have something somewhat memorized (path-finding), but even that is pretty basic, and I think they would have accepted non-optimal solutions that worked anyway, so really all you needed to know how to do was write a BFS that maintains the cost of the shortest-yet found path to each expanded vertex. The rest I think anybody - given enough time - could solve if they were a good programmer. Of course sometimes there are problems where you don't figure it out in time, and definitely (a minority of) problems that are too hard for a whiteboard interview, but you're not going to get every technical question right anyway. It increases the stochasticity of interviewing when you can fail the technical challenges of interviews for jobs you, on another interviewing day/with another set of question, would otherwise qualify for, but this is logical from a hiring perspective. It costs less to interview 20 people and accept one qualified candidate than to interview 5 people and accept an unqualified candidate. It's not that you need to know how to solve these problems to be a good programmer, or even that being able to solve these problems is indicative of a good programmer, it's that a bullshitter/unqualified candidate will fail these every time, while at least a few qualified candidates won't fail.

Franciscouzo 9y ago
Finding the optimal longest palindrome substring algorithm surely is in the "you'll only get this if you've seen it before" territory. Implementing a binary search algorithm is anything but trivial, you've got overflows, off-by-one errors, passing arguments by value, etc. Sure, the idea of finding the point in the array that starts decreasing with a binary search is simple, but the subtle ways you can write it wrong are practically infinite.
- 9y ago

muzani 9y ago

They're sort of like how the military would judge physical fitness by the number of push ups one can do. It correlates with skill in general, but it biases towards people who practice it.

arca_vorago 9y ago
Which is sorta the point of the pft.

sjellis 9y ago

> Why can't the industry finally just drop stupid whiteboard coding and move on to more practically focused questions? Cynically, I wonder if it's sometimes because it's a crutch for the interviewers. Like anything else, interviewing is a skill that you learn through interest, study and practice. I've been carrying out technical interviews for years, and still wouldn't say that I get it right every time. If the interviewers have not made an effort to learn how to do interviews, or don't really want to do them, or don't actually know what the job will involve, then they can just fall back on asking algorithm questions.