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Data structures and algorithms I actually used while working at tech companies

blog.pragmaticengineer.com

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Re: Data structures and algorithms I actually used while working at tech companies

#451

Post by jefftk »

cmroanirgo wrote: post #423
dmoy wrote: post #336

Earlier quoted context omitted.

Yea I interview (and have sat on HC) at Google, and interviewers who ask these types of questions really frustrate me. If your question requires having previously memorized or being able to come up with some tricky algorithm on the fly in 45 minutes and code a solution using it , your question is probably bad. I get why they ask them - they're easy to ask, they're easy to score, and when your question inevitably gets…

What on earth is wrong with asking to see the interviewee's code? Skim over it looking for neatness, how they comment, what build procedure is there and quiz them about what you see: anything from language choice, to build reproducibility, from architecture to install. And of course quiz them on algos you see. All of these 'tricky' exam style questions don't show a thing about the person sitting in the interview room…

In addition to the sibling's excellent "candidates who work at companies that don't let them show you their current code, and have a home life that occupies their time outside of work", here's another category of candidates you lose: people who code differently in their downtime than they do at work.

If you looked over my github, you would see most of my commits are ones that, at work, I wouldn't accept from anyone. The code is sloppy, there are no tests, it looks like someone was just trying to get something working as quickly as possible with no thought for maintainability or understandability. But, of course, that's exactly what I was doing! When I code in my spare time, I'm solving problems that I've run into in my spare time, and I approach it very differently from in my work life. The constraints are different, and so the solutions are different.

Re: Data structures and algorithms I actually used while working at tech companies

#452

Post by pps43 »

duskwuff wrote: post #439
pps43 wrote: post #188

Earlier quoted context omitted.

> more elegant and simpler Beauty is in the eye of the beholder, but a loop is hard to beat as far as simplicity goes, and you don't depend on your compiler being clever enough to optimize tail recursion. If you need to traverse a tree then sure, but with Fibonacci you don't even need the stack to begin with. You only need to keep a previous number.

You don't even need a loop. Binet's formula gives a closed-form expression for the Fibonacci sequence. (And of course I don't remember that formula off the top of my head, but I know it exists, so I'd be 90% of the way to solving a problem which required it.)

This will open another can of worms (floating point errors).

Re: Data structures and algorithms I actually used while working at tech companies

#453

Post by dzonga »

whack wrote: post #228

I'm increasingly convinced that Algorithms-and-Data-Structure interviews are essentially being used as a proxy for: - General IQ. Can this person understand and apply complex ideas - Grit. Is this person hard-working enough to learn things that take time and effort It's the software equivalent of the NFL scouting combine. The goal is not to create a test that is similar to the day-to-day job. But rather, create a tes…

remember, players opt out of the combine. and a good portion do, if they have a dope highlight reel. though they will conduct interviews with the gm for personality what we call in the tech field: "cultural fit"

Re: Data structures and algorithms I actually used while working at tech companies

#454

Post by dyno_for_days »

Darvon wrote: post #322
notacoward wrote: post #257

Earlier quoted context omitted.

Unfortunately, those kinds of interviews also select for some other things that they shouldn't. * Youth. People who have very recently studied these things in school, and use the same languages as the interviewers, have an advantage. * Free time. People who have families (for example) might have less free time to study "Cracking the Code Interview" and such. * Absence of anxiety. This disadvantages women, minorities,…

I'd hate working alongside a young anxiety free conformist who doesn't have external commitments.

This is an underrated hilarious comment

Re: Data structures and algorithms I actually used while working at tech companies

#455

Post by stevula »

wenc wrote: post #264
notacoward wrote: post #257

Earlier quoted context omitted.

Unfortunately, those kinds of interviews also select for some other things that they shouldn't. * Youth. People who have very recently studied these things in school, and use the same languages as the interviewers, have an advantage. * Free time. People who have families (for example) might have less free time to study "Cracking the Code Interview" and such. * Absence of anxiety. This disadvantages women, minorities,…

> Resistance to anxiety. This disadvantages women, minorities, and people with psychological conditions that should be covered by ADA. I resemble some of those categories, and I don't know if I would feel comfortable making the leap to correlate them to a some inherent reduced level of resistance to anxiety. That seems like a generalization which I feel that, on an aggregate level, seems unsupportable by data. I thin…

I don’t know about “resistance to anxiety”, but it can certainly be anxiety-inducing to be the only member of a given minority in the interviewing room (or entire floor, as is sometimes the case in tech).

Re: Data structures and algorithms I actually used while working at tech companies

#456

Post by Swizec »

dragonsngoblins wrote: post #448
Swizec wrote: post #411

Earlier quoted context omitted.

Funnily that old style of question is far closer to my day-to-day as an engineer than a leetcode algorithms question. Most of my job involves figuring out solutions to fuzzy problems based on unknown constraints, undiscovered requirements, and often unclear end-goals. "How would you fill this airplane with golf balls?" is a fantastic question. If the candidate doesn't reply with "Why? What are you really trying to ac…

I suppose it depends on how you grade the answers. Like I have bad spatial awareness in terms of how big things like planes are. I genuinely don't really have an idea how long a commercial airliner is, or how big a ping pong ball is. I feel like I'd do ok if I could get reasonable approximate values for things like the size of the plane, the balls, the seats, etc. if I also have to supply those values myself the end…

Like I said, the point of this question isn’t to seek your domain expertise, the point is to see how you use other people’s domain expertise to create a [software] system.

Re: Data structures and algorithms I actually used while working at tech companies

#457

Post by throwaway12369 »

Swizec wrote: post #341
dmoy wrote: post #336

Earlier quoted context omitted.

Yea I interview (and have sat on HC) at Google, and interviewers who ask these types of questions really frustrate me. If your question requires having previously memorized or being able to come up with some tricky algorithm on the fly in 45 minutes and code a solution using it , your question is probably bad. I get why they ask them - they're easy to ask, they're easy to score, and when your question inevitably gets…

My favorite question to ask in software engineering interviews is one that I believe to be un-burnable. > It's 2140 AD, New York is under water up to X feet high. Buildings have been retrofitted with to withstand the water. You are in charge of keeping your building dry. If water gets in and damages the foundation, a few thousand people die or become homeless. > Design a system that ensures that doesn't happen. How c…

It’s unfortunate that this bizarre and arbitrary stab at analytical thinking assessment is still used to evaluate the skill of software developers.

Here’s another idea: have them write software. Not algorithm trivia, but actual software. Keep the scope small so there isn’t an onerous time commitment and have them explain their choices.

Re: Data structures and algorithms I actually used while working at tech companies

#458

Post by eyelidlessness »

jkingsbery wrote: post #327

Early in my career, I interviewed at Google. One of the interviewer asked me to recite the algorithm for constructing a Convex Hull. Since I hadn't done anything related to convex hulls since my algorithms class as a sophomore in college (several years earlier), I couldn't remember all the details. At some point, I said, I know where in CLRS ( https://www.amazon.com/Introduction-Algorithms-3rd-MIT-Press... ) this is.…

“I would probably look it up” is the correct answer unless you’re interviewing for a very specialized role. I had a similar experience interviewing at google (and I regret not walking out), and a much more pronounced experience at MS (where I did walk out and don’t regret it).

Re: Data structures and algorithms I actually used while working at tech companies

#459

Post by hackermailman »

ojr wrote: post #236
whack wrote: post #228

I'm increasingly convinced that Algorithms-and-Data-Structure interviews are essentially being used as a proxy for: - General IQ. Can this person understand and apply complex ideas - Grit. Is this person hard-working enough to learn things that take time and effort It's the software equivalent of the NFL scouting combine. The goal is not to create a test that is similar to the day-to-day job. But rather, create a tes…

- Retention. If this person spent hours on leetcode, they’ll be less likely to leave the job knowing the effort it takes to get through the gate

I had the opposite experience, once you grind problems on leetcode and figure them out yourself, you somehow never forget them, esp under pressure in an interview. The problems aren't exactly the same of course but like Polya's book "how to solve it" describes solving a problem by considering something similar you solved, when presented with some interview problem to work through the first things that came to my mind each time were previous silly leetcode solutions I came up with that bought me some time instead of blanking out.

Re: Data structures and algorithms I actually used while working at tech companies

#460

Post by pldr1234 »

whack wrote: post #228

I'm increasingly convinced that Algorithms-and-Data-Structure interviews are essentially being used as a proxy for: - General IQ. Can this person understand and apply complex ideas - Grit. Is this person hard-working enough to learn things that take time and effort It's the software equivalent of the NFL scouting combine. The goal is not to create a test that is similar to the day-to-day job. But rather, create a tes…

This is correct. It's unfortunate, but unless you can mandate Google to change their entire interviewing regime, you have to simply understand that this is the perspective, and move forward demonstrating yourself against this criteria, whatever else you may think.
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