4 ms·

You and a lot of other commenters are getting hung up on the BFS example. It's just that - an example. There are dozens of algorithms that are "common" enough t

by spyspy 8y ago

You and a lot of other commenters are getting hung up on the BFS example. It's just that - an example. There are dozens of algorithms that are "common" enough to be asked about and diminishing returns to having them all memorized.

cornellwright 8y ago
Sure, but that's my point. So long as the interviewer is telling you what they'd actually like you to do, you should be able to just derive the algorithm you need to do it. At some point the algorithms become difficult enough (particularly if you add lots of constraints like efficiency) that it's pretty unreasonable to expect that in an interview though, and at that point it's a bad question. Rather than memorizing a thousand algorithms, I generally focus on being able to solve problems simply, quickly, and elegantly, which will help in actually doing most jobs.
- pishpash 8y ago
  You're still not getting it. Even for BFS, which is not a hard problem, the current state of the market is that enough people have memorized the BFS recipe so that the interview doesn't allocate much of any time to it. You're not going to have/be given time to "just derive the algorithm" or "solve problems simply, quickly, and elegantly." You're competing against rote speed, which, if you don't implement BFS all day or haven't recently done interview prep, you don't have and you're definitely going to fail. I've heard people actually defend these useless interviews on correlation grounds, like people who are docile, follow the herd, and "prepare" are good hard-working workers who also tend to have done well in school or look polished in other aspects of life. That's what these interviews are really looking for. So, if you're not a well known expert, suck it up, be a servile cog and follow the script.
  - skybrian 8y ago
    It seems like there might be a middle ground, like being willing to play the game, that doesn't imply being "a servile cog?" The trick seems to be knowing when the game is worth playing. There are certainly situations where competition is too fierce and requires too much preparation, so it's not worth doing if you don't really enjoy the game. I'm not sure getting hired at a large tech firm is quite that competitive, though? They do hire lots of people all the time.
- nicoburns 8y ago
  My first reaction when inplementing anything more than a very simple algorithm is to google the best way to do it. Of course, I could probably come up with a way to do it by myself. I could probably even come up with an efficient way if I spent an afternoon/day on it. But why do that when I can google it, and get 3 blog posts and 2 stack overflow answers detailing the different options and the trade offs between them, most likely even with an implementation I can base mine off of? That's why these interview situations are stupid. They're like school where copying is cheating, whereas in real-world situations copying is a great way of doing something.
  - smallnamespace 8y ago
    > But why do that when I can google it, and get 3 blog posts and 2 stack overflow answers detailing the different options and the trade offs between them, most likely even with an implementation I can base mine off of? A lot of resources out there are wrong, inaccurate, or not reasonable for your particular context, and it requires a reasonable amount of algorithmic intelligence to be able to sniff out what's appropriate. If I had a dollar for every high-upvoted SO post that misstates a problem or doesn't offer proper caveats... but I can make that judgment because I've already thought about a related problem in the past. It's like asking why one should learn how to write properly when Grammarly and spell checkers exist, or why mental arithmetic is useful when we have calculators—at some point those your tools will be inappropriate or unavailable. Search tools are force multipliers, not replacements for personal knowledge and intuition.
    - nicoburns 8y ago
      > A lot of resources out there are wrong, inaccurate, or not reasonable for your particular context, and it requires a reasonable amount of algorithmic intelligence to be able to sniff out what's appropriate. Right, and having that algorithmic intelligence is key part of me being a good developer. But testing how someone implements an algorithm in time-scarce circumstances is not a good test of that kind of intelligence because it is likely to favour people who have been exposed to that particular algorithm before (even if they only rote-learnt information about it - as many interviewees seem to do in practice) over people who have the capability to think deeply and reason correctly about it, but have not previously been exposed to that problem.
Vel0cityX 8y ago
Except you don't need to have them _memorized_. You shouldn't. That's not the point.
- ec109685 8y ago
  But given it is straightforward to memorize, it isn’t a good test.
- Datsundere 8y ago
  Except all of these questions can be grouped into a category of the same kinds of problem and it is in fact spending time to find out that pattern and which category from sliding window, nested intervals, recursion and dynamic programming it belongs to
- TrinaryWorksToo 8y ago
  If you memorize them you appear more competent

by spyspy 8y ago

cornellwright 8y ago

Sure, but that's my point. So long as the interviewer is telling you what they'd actually like you to do, you should be able to just derive the algorithm you need to do it. At some point the algorithms become difficult enough (particularly if you add lots of constraints like efficiency) that it's pretty unreasonable to expect that in an interview though, and at that point it's a bad question. Rather than memorizing a thousand algorithms, I generally focus on being able to solve problems simply, quickly, and elegantly, which will help in actually doing most jobs.

pishpash 8y ago
You're still not getting it. Even for BFS, which is not a hard problem, the current state of the market is that enough people have memorized the BFS recipe so that the interview doesn't allocate much of any time to it. You're not going to have/be given time to "just derive the algorithm" or "solve problems simply, quickly, and elegantly." You're competing against rote speed, which, if you don't implement BFS all day or haven't recently done interview prep, you don't have and you're definitely going to fail. I've heard people actually defend these useless interviews on correlation grounds, like people who are docile, follow the herd, and "prepare" are good hard-working workers who also tend to have done well in school or look polished in other aspects of life. That's what these interviews are really looking for. So, if you're not a well known expert, suck it up, be a servile cog and follow the script.
- skybrian 8y ago
  It seems like there might be a middle ground, like being willing to play the game, that doesn't imply being "a servile cog?" The trick seems to be knowing when the game is worth playing. There are certainly situations where competition is too fierce and requires too much preparation, so it's not worth doing if you don't really enjoy the game. I'm not sure getting hired at a large tech firm is quite that competitive, though? They do hire lots of people all the time.
nicoburns 8y ago
My first reaction when inplementing anything more than a very simple algorithm is to google the best way to do it. Of course, I could probably come up with a way to do it by myself. I could probably even come up with an efficient way if I spent an afternoon/day on it. But why do that when I can google it, and get 3 blog posts and 2 stack overflow answers detailing the different options and the trade offs between them, most likely even with an implementation I can base mine off of? That's why these interview situations are stupid. They're like school where copying is cheating, whereas in real-world situations copying is a great way of doing something.
- smallnamespace 8y ago
  > But why do that when I can google it, and get 3 blog posts and 2 stack overflow answers detailing the different options and the trade offs between them, most likely even with an implementation I can base mine off of? A lot of resources out there are wrong, inaccurate, or not reasonable for your particular context, and it requires a reasonable amount of algorithmic intelligence to be able to sniff out what's appropriate. If I had a dollar for every high-upvoted SO post that misstates a problem or doesn't offer proper caveats... but I can make that judgment because I've already thought about a related problem in the past. It's like asking why one should learn how to write properly when Grammarly and spell checkers exist, or why mental arithmetic is useful when we have calculators—at some point those your tools will be inappropriate or unavailable. Search tools are force multipliers, not replacements for personal knowledge and intuition.
  - nicoburns 8y ago
    > A lot of resources out there are wrong, inaccurate, or not reasonable for your particular context, and it requires a reasonable amount of algorithmic intelligence to be able to sniff out what's appropriate. Right, and having that algorithmic intelligence is key part of me being a good developer. But testing how someone implements an algorithm in time-scarce circumstances is not a good test of that kind of intelligence because it is likely to favour people who have been exposed to that particular algorithm before (even if they only rote-learnt information about it - as many interviewees seem to do in practice) over people who have the capability to think deeply and reason correctly about it, but have not previously been exposed to that problem.

Vel0cityX 8y ago

Except you don't need to have them _memorized_. You shouldn't. That's not the point.

ec109685 8y ago
But given it is straightforward to memorize, it isn’t a good test.
Datsundere 8y ago
Except all of these questions can be grouped into a category of the same kinds of problem and it is in fact spending time to find out that pattern and which category from sliding window, nested intervals, recursion and dynamic programming it belongs to
TrinaryWorksToo 8y ago
If you memorize them you appear more competent