Google Interview Questions Deconstructed: The Knight’s Dialer • Hacker News Board

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#31

Post by murgindrag » Wed, Oct 07, 2020, 7:19 PM UTC

So here's the thing. And I know I'll get knocked to r/iamverysmart for this. It timed myself. It took less than 10 minutes from reading the problem to coding up a working dynamic programming solution (no peaking at the rest of the article). A big chunk of that was (unsuccessfully) trying to come up with a closed-form solution.

I didn't get the log(n) solution until I found it existed at the bottom, but once the author mentioned it's existence, that took less than 5 minutes to figure out. I didn't code that up, though.

I'm probably an above-average programmer, but I'm not a 99.99% outlier. I interviewed early Google. The questions were tough for me (much more so than this one).

Things which jumped out at me: "The better the candidate, the fewer hints I tend to have to give, but I have yet to see a candidate who required no input from me at all."

I read this as "We're scraping the bottom of the barrel for candidates. Our candidates are nothing like those who applied to Google circa 2000"

And: "I didn’t even know it existed until one of my colleagues came back to his desk with a shocked look on his face and announced he had just interviewed the best candidate he’d ever seen."

I read this as: "Our employees are dumb. In using this interview question for years, none of us ever noticed the obvious."

What's going on there? I mean I can see messing up an interview question like this under the stress of an interview (I literally confused linked lists and arrays in probably my worst interview ever). But no candidate? Ever? And no employee? Come on.

There's something deeply wrong at Google. It's been deeply wrong for a few years. I hope someone fixes it.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#32

Post by pc86 » Wed, Oct 07, 2020, 7:21 PM UTC

happytoexplain wrote: post #14

username90 wrote: post #9

Earlier quoted context omitted.

This isn't a brain teaser, they actually correlate with on-the-job performance. When I worked at Google I looked up their internal reports on the subject and they showed that the score people got on these algorithm interviews correlated pretty well with their performance ratings after they got hired. In other words the group of people who got hired even though they had low scores performed significantly worse than th…

Personally, I don't think correlation is good enough. I never doubted that people who are good with a single given abstract problem are correlated with people who are good candidates. So yes, it non-arbitrarily identifies good candidates, but it also arbitrarily eliminates a significant chunk of good candidates.

Eliminating good candidates is not in and of itself a bad thing if it a) decreases your risk of a bad hire, and b) you want to optimize to decrease the risk of a bad hire at the expense of eliminating some potentially great ones.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#33

Post by blahyawnblah » Wed, Oct 07, 2020, 7:21 PM UTC

jeffbee wrote: post #29

It might not be obvious but these kinds of questions are terrible for diversity and inclusion because they incorporate too much cultural knowledge that is not universal. A person who has never seen chess will spend more of the interview just trying to figure out what is meant by the Knight's move. That disadvantages people from low-chess cultures, no matter how qualified and intelligent they may be. Chess also has a…

I doesn't take long to understand how a knight moves, though. Move two squares in a direction and then move one square perpendicular to that.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#34

Post by toast0 » Wed, Oct 07, 2020, 7:22 PM UTC

throwaways885 wrote: post #13

joshuamorton wrote: post #4

Earlier quoted context omitted.

This isn't a brainteaser. It's a programming problem. Brainteasers are like "how many ping pong balls fit in a 747" or "you wake up an inch tall in a blender, the blades start spinning in a minute. How do you survive."

> how many ping pong balls fit in a 747 This one does seem useful. Being able to do back-of-the-napkin (i.e. fermi problem) calculations is a pretty good skill.

It might be an OK problem if the interviewee is familiar with 747s and ping pong balls, and will be interacting with physical objects as part of their job. I have a terrible time with physical measurments and area and space, but thankfully it's not relevant to my work.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#35

Post by xienze » Wed, Oct 07, 2020, 7:22 PM UTC

mym1990 wrote: post #30

Is it just me or is it somewhat pointless to be lamenting the fact that this may or may not be a terrible part of the hiring process? At the end of the day if you sit down for the interview and are given this question, you can either do your best to solve it or walk out of the interview and go to a company that you feel is 'more worth your time'. When you're playing by Google's rules, there's not much to be accomplis…

> you can either do your best to solve it or walk out of the interview and go to a company that you feel is 'more worth your time'.

The problem is so many other companies have copied this practice because hey, Google asks brainteasers and gets the best candidates, so we should do it too!

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#36

Post by UncleMeat » Wed, Oct 07, 2020, 7:22 PM UTC

mym1990 wrote: post #30

Is it just me or is it somewhat pointless to be lamenting the fact that this may or may not be a terrible part of the hiring process? At the end of the day if you sit down for the interview and are given this question, you can either do your best to solve it or walk out of the interview and go to a company that you feel is 'more worth your time'. When you're playing by Google's rules, there's not much to be accomplis…

It isn't pointless. Criticizing leetcode style interviews produces an infinite supply of social media comments and upvotes. The conversation will never progress, but it lets people argue on the internet, which is a key value proposition of headlines today.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#37

Post by pc86 » Wed, Oct 07, 2020, 7:23 PM UTC

gcheong wrote: post #16

username90 wrote: post #9

Earlier quoted context omitted.

This isn't a brain teaser, they actually correlate with on-the-job performance. When I worked at Google I looked up their internal reports on the subject and they showed that the score people got on these algorithm interviews correlated pretty well with their performance ratings after they got hired. In other words the group of people who got hired even though they had low scores performed significantly worse than th…

How do they control for bias in that a person with a high or low score may just be perceived to do better or worse, may be given better or less opportunities, etc. if their scores are known to the managers, etc? In other words it’s a correlation but is is explanatory?

Why would managers get employees' scores on random interview questions? Why would that affect project assignments months or years later? Why would we assume folks at Google in charge of creating effective interview processes wouldn't be capable of the most basic statistical analysis, by making sure they had a large enough sample, enough performance reviews for each employee, etc?

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#38

Post by Judgmentality » Wed, Oct 07, 2020, 7:23 PM UTC

username90 wrote: post #20

noitpmeder wrote: post #12

Earlier quoted context omitted.

/r/iamverysmart/

What is your point? Companies wants to hire smart people which is why they have these interviews. This applies no matter what level people are at. "I forgot" isn't valid defense. All the people in these threads who says things like "I knew this but forgot" are really cringy.

/r/woosh

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#39

Post by gedy » Wed, Oct 07, 2020, 7:23 PM UTC

username90 wrote: post #9

warmfuzzykitten wrote: post #3

Typical brain-teaser interview question that will have absolutely no correlation to on-the-job performance but makes the interviewer feel really smart. I thought Google had gotten away from these.

This isn't a brain teaser, they actually correlate with on-the-job performance. When I worked at Google I looked up their internal reports on the subject and they showed that the score people got on these algorithm interviews correlated pretty well with their performance ratings after they got hired. In other words the group of people who got hired even though they had low scores performed significantly worse than th…

Maybe for Google-type/scale problems, but I'd say that the engineers I've worked with and hired for "normal" software jobs (e.g. here's a boring business domain, make it CRUD, make an API, make a UI for it) - there is almost an inverse correlation between being a CS/algorithm genius and being happy/successful at these everyday roles.

From observation, many super sharp CS people very frequently want to write systems from scratch, get bored, then move on. It's really hard to pull them back to use off-the-shelf tech, don't over optimize, etc. Many of the best folks I've worked with in these roles are not CS majors at all (EE, ECE, etc) and this algo screening would filter them out.

Re: Google Interview Questions Deconstructed: The Knight’s Dialer

#40

Post by mym1990 » Wed, Oct 07, 2020, 7:23 PM UTC

jeffbee wrote: post #29

It might not be obvious but these kinds of questions are terrible for diversity and inclusion because they incorporate too much cultural knowledge that is not universal. A person who has never seen chess will spend more of the interview just trying to figure out what is meant by the Knight's move. That disadvantages people from low-chess cultures, no matter how qualified and intelligent they may be. Chess also has a…

While I get this sentiment, and agree with it, I would like to also point out that there are almost no clear cut and dry problems in the real world. One needs to be able to know how to ask questions in order to get a good enough grasp to begin formulating some kind of solution.

When you are taking an SAT question, there is no opportunity to ask 'can you tell me how tennis is scored?' That is not the case in some/most interviews.