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Google Interview Questions Deconstructed: The Knight’s Dialer

alexgolec.dev

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

#21

Post by watwut »

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.

Back of napkin that requires you to know what 747 is wrong be correlated with anything programming related.

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

#22

Post by Jabbles »

username90 wrote: post #2

Counting the number of paths when you have loops is easiest using a connection matrix and matrix exponentiation. Then you get log(n) time.

That is covered in the next blogpost: https://alexgolec.dev/knights-dialer-logarithmic-time-editio...

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

#24

Post by threatofrain »

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…

General mental ability is regularly affirmed as one of the most predictive factors for successful hires, it's just that it has a questionable legal history.

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

#25

Post by crocal »

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.

Actually a typical GMAT question...

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

#26

Post by vsareto »

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.

>but it also arbitrarily eliminates a significant chunk of good candidates.

I think they know that and they're okay with it because they have the volume and cash. I think they routinely tell you to try again.

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

#27

Post by umaar »

On the subject of Google Interview challenges and keypads, I wrote about a Google keypad challenge here: https://umaar.com/blog/my-code-exercise-submissions-part-1/ - it's all about outputting keypad directions such as "right, right, ⏎" based on the desired input.

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

#28

Post by thdc »

joshuamorton wrote: post #4
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 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."

I agree that this isn't a brainteaser.

The problem itself appears to be nonsensical with no real world value but as long as it is a well defined problem with a concrete solution then it should be fine. Ideally the interviewer should be looking for how you approach the problem and what you do to obtain an answer (whether they do or not is a separate topic)

Granted, the 747 question also technically does have a concrete solution I guess, but I would end up asking things like what's the volume of a 747 and the dimensions of a ping pong ball and then point out there will be gaps as we fill the 747 with balls so it's not simply dividing the volumes, write a program based on these observations, give a disclaimer that it will most likely be inaccurate, and hope that is good enough to pass.

But that blender question... uh yeah... I'd probably spend too much time asking clarifying questions to actually come up with something plausible.

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

#29

Post by jeffbee »

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 class aspect, so you are biasing against class background as well.

This is the same reason why they had to stop writing SAT questions that started out "Tad and Buffy are at duece in the fifth set of their tennis match ...".

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

#30

Post by mym1990 »

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 accomplished in the form of complaining.

My guess is that many hiring practices will change(and are changing) over time based on the internal work that people are doing to drive better initiatives, and less based on comments on HN.

Personally, I would like to see what people thing about the actual solution to this particular problem...

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