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Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

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Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#31

Post by kamaal »

fsloth wrote: post #14
LandR wrote: post #5

Earlier quoted context omitted.

The only reason it seems to even learn them is to pass an interview... What a utterly stupid and broken process. All it's testing is recall, that you've memorized some algorithms that 99% of developers will never need. Especially when these are really hard problems that people have studied for years, to think that anyone who hasn't memorised the solution is working this stuff out in an hour on a whiteboard is crazine…

"these are really hard problems that people have studied for years" Because of this. So that when you encounter a problem, you know how it can be solved efficiently. If you disregard existing knowledge, you are likely to spend a lot of time cooking up something complex and half-assed that creates an unnecessary maintenance load. Like music is composed of fundamentals, similarly most problems in computing can be decom…

>>If you disregard existing knowledge, you are likely to spend a lot of time cooking up something complex and half-assed that creates an unnecessary maintenance load.

Unless you are stuck on an Island coding during a vacation, not one person on earth faces this kind of a situation.

Almost anybody doing anything apart from basic beginner level coding work knows to look up to a solution on the internet if a solution is not scaling already.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#32

Post by lynal »

Silhouette wrote: post #24
elromulous wrote: post #6

Earlier quoted context omitted.

I think that was meant to be a hyperbole.

Indeed, although it's not unheard of for mathematics lecturers at university to throw in a question within a twenty-question problem sheet for their course that is actually equivalent to some important unsolved problem, on the off chance that one of their students sees things in a totally new way and makes a ground-breaking discovery. Solving something NP-hard in linearithmic time would certainly qualify...

Do you have a cite/example of a lecturer doing that on an exam? Are there any examples where that has been successful?

I had never heard of that happening! It would be extremely cool if it ever worked.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#33

Post by wyldfire »

dekhn wrote: post #2

I work for Google and have never been good at the "Here's an NP-hard problem you haven't heard of, write correct code for nlogn solution on whiteboard in language of choice" question. I had to train extensively (reading CLR, practicing) to be able to pass. However, large numbers of engineers at Google are very good at solving whiteboard questions. A lot of it comes from practice, a lot comes from knowing the common p…

> I had to train extensively (reading CLR, practicing)

I didn't know what "CLR" was, so I searched around: Cormen, Leiserson, Rivest's "Introduction to Algorithms" [1].

[1] https://en.wikipedia.org/wiki/Introduction_to_Algorithms

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#34

Post by superice »

kamaal wrote: post #27
jfasi wrote: post #12

I often do, both for fun and to prepare myself to give a question I'd like to use in an interview. The thing about interview questions at Google is there's a very fine line they need to walk: if they're too easy they give no useful information about the candidate, and if they're too hard they can never be solved in 45 minutes, again yielding no useful information. You also need to be able to provide some hints, becau…

>>Sure you can write a for loop to iterate over a data set, but will you fall on your face when that data set is petabytes in size? I understand what you are trying to say here. But how many candidates are capable of inventing path breaking algorithms in 45 minutes, just to crack a job interview? I guess only a countable people in the world could achieve a feat that amazing, where they could invent a totally new nove…

> There is nothing novel in merely knowing an algorithm. And you also have not tested a person's ability in inventing an algorithm either.

The goal of this is too test whether the interviewee can recognize that this is a case to apply this algorithm in. It pattern recognition, not memorization, that is being tested here.

Whether that is particularly useful is of course the million dollar question.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#35

Post by trocadero »

lynal wrote: post #32
Silhouette wrote: post #24

Earlier quoted context omitted.

Indeed, although it's not unheard of for mathematics lecturers at university to throw in a question within a twenty-question problem sheet for their course that is actually equivalent to some important unsolved problem, on the off chance that one of their students sees things in a totally new way and makes a ground-breaking discovery. Solving something NP-hard in linearithmic time would certainly qualify...

Do you have a cite/example of a lecturer doing that on an exam? Are there any examples where that has been successful? I had never heard of that happening! It would be extremely cool if it ever worked.

Not an exam but:

>An event in Dantzig's life became the origin of a famous story in 1939, while he was a graduate student at UC Berkeley. Near the beginning of a class for which Dantzig was late, professor Jerzy Neyman wrote two examples of famously unsolved statistics problems on the blackboard. When Dantzig arrived, he assumed that the two problems were a homework assignment and wrote them down. According to Dantzig, the problems "seemed to be a little harder than usual", but a few days later he handed in completed solutions for the two problems, still believing that they were an assignment that was overdue.[4][7]

>Six weeks later, Dantzig received a visit from an excited professor Neyman, who was eager to tell him that the homework problems he had solved were two of the most famous unsolved problems in statistics

https://en.wikipedia.org/wiki/George_Dantzig

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#36

Post by habosa »

I work at Google and no it's not easy for us either. I've heard many of my coworkers joke that if they went through the interview process again they'd probably fail.

That said I see two kinds of interviewers. One kind (the good kind) takes a medium difficulty question and uses it to explore the candidate's coding, algorithms, communication, and problem solving skills.

The other kind has a super hard question with a single algorithmic solution that tells you nothing about what kind of engineer the person would be. This kind of interviewer takes too much pleasure in being a gatekeeper to Google.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#37

Post by kamaal »

mlevental wrote: post #29
kamaal wrote: post #27

Earlier quoted context omitted.

>>Sure you can write a for loop to iterate over a data set, but will you fall on your face when that data set is petabytes in size? I understand what you are trying to say here. But how many candidates are capable of inventing path breaking algorithms in 45 minutes, just to crack a job interview? I guess only a countable people in the world could achieve a feat that amazing, where they could invent a totally new nove…

i don't understand why people do this. you're raging against a machine. do you think you're going to change this person's mind on how effective whiteboard questions are?

No, but it helps to highlight the pointlessness of these methods in hiring people for a real world project.

I keep hearing, how startups use multiple online judge algorithm screening sessions, to filter and hire the best. But the candidates just can't do any real world work, because they are busy practicing interview questions for the next job they seek while they are in their current jobs.

In other words you are optimizing to hire people who are good at clearing interviews, not doing their day job- Because they have to be bad enough at day jobs, as they have to be practicing these algo questions all day to clear your interviews.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#38

Post by [deleted] »

lynal wrote: post #32
Silhouette wrote: post #24

Earlier quoted context omitted.

Indeed, although it's not unheard of for mathematics lecturers at university to throw in a question within a twenty-question problem sheet for their course that is actually equivalent to some important unsolved problem, on the off chance that one of their students sees things in a totally new way and makes a ground-breaking discovery. Solving something NP-hard in linearithmic time would certainly qualify...

Do you have a cite/example of a lecturer doing that on an exam? Are there any examples where that has been successful? I had never heard of that happening! It would be extremely cool if it ever worked.

[deleted]

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#39

Post by C4stor »

kamaal wrote: post #28
gumby wrote: post #18

Earlier quoted context omitted.

> The only reason it seems to even learn them is to pass an interview... While I agree that the process is broken, a solid understanding of algorithms and data structures is very important for developers at my company. And nobody knows all , or even most of the algos or data structures! But we do have large amounts of data and some pretty complex analytic problems, and a poor design can cost a lot of time and AWS $.…

Those look like software design skills. Also the type of systems you describes use something like Hadoop, and use things like Hive and Pig on top of it. Once you get the data out you use Python or R. And you generally use a standard library to work with. That really SQL + general programming. What new problems are you working on that require you to invent novel algorithmic techniques?

Even after choosing a technology (like Hadoop), there's a lot of difference between the best and the worst algorithm to solve a problem.

For example, the reduce phase of MapReduce is pretty much "apply the algorithm you want on this List", and that's where knowing good list algorithms (for example) shine.

Re: Ask HN: Can engineers from Google or Facebook solve whiteboard questions easily?

#40

Post by [deleted] »

lynal wrote: post #32
Silhouette wrote: post #24

Earlier quoted context omitted.

Indeed, although it's not unheard of for mathematics lecturers at university to throw in a question within a twenty-question problem sheet for their course that is actually equivalent to some important unsolved problem, on the off chance that one of their students sees things in a totally new way and makes a ground-breaking discovery. Solving something NP-hard in linearithmic time would certainly qualify...

Do you have a cite/example of a lecturer doing that on an exam? Are there any examples where that has been successful? I had never heard of that happening! It would be extremely cool if it ever worked.

[deleted]
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