What I would call puzzle problems usually involve some trick to getting the answer. If you can't figure out the trick, you're stumped. If you know the trick, you barely have to think to crank out the answer. Optimally solving the example in the article is one of those.
They weren't widely banned because they were too novel and charming. They were banned because "time to aha!" in any given instance doesn't tell you much about how someone solves problems. Also, because the bulk of the work at most jobs doesn't really resemble seeking "aha moments," these questions tend to select for people who thrive most on doing something other than the job at hand.
[1] https://en.wikipedia.org/wiki/Fermi_problem
[2] https://blog.codinghorror.com/the-hardest-interview-puzzle-q...
I can only imagine being "charmed" by a question like if I was much younger in my career, eager to be seen as smart and in the company of like-minded folk.
Nowadays... my focus is on solving problems... as in real problems, not made-up ones. Thankfully I haven't heard questions like this in years. But when I do, I take it as a sign that they probably don't have actual, meaty problems to work on, that is, requiring higher-level cognitive skills (and actual experience). Not to mention that this was supposed to be lunch, and here they are asking filter questions, but pretending it's just "casual conversation" when obviously it isn't.
And so would probably pause for a second, and think of a way to tactfully end the interview, and thank the interviewer for their time.
This is about empathetically understanding the stress levels between both of you would have been miles apart. Unless the candidate had brought up the subject somehow it'd have been nicer to just try to relax them and get to know them informally by asking about them - or better yet letting them do their own thing for lunch if they wanted.
is this a technical puzzle/question? to me it reads like a middle school geometry question. it would be fun to discuss it with friends/colleagues but I wouldn't expect it during a software engineering interview
> Although finding the answer requires only basic geometry, even professional mathematicians find the answer strangely counter-intuitive.
I guess the more a visual person you are the more counter-intuitive it is. That only 6 feet of rope is needed to widen the radius of Earth at every place at continents and oceans ect at a whole 1 feet seems crazy to me.
I still fail to see how this is relevant for a technical interview, assuming that we're trying to hire a software engineer. Fun, but not relevant.
That is unexpected!
- What is the rope made of? How stretchy is it? How strong is it to tensile stresses?
- What model of the earth are we using? A sphere (circular cross-section?) ellipsoid? Which axis of the ellipsoid? Does it take terrain into effect, or just gravitation? How does the rope avoid hitting terrain?
- How does the rope stay suspended? how does it resist gravity? are there uniform thrusters on it? How are they fueled?
- How is length added to the rope? Is it stretched somehow? Material added? How is the added material, if applicable, inserted?
Maybe the job interview is for Space X and they're working on some new system of mini-satellites-on-a-rope called Hyper-rope, or maybe google is trying to pivot their failed Loon project into some kind of air-born connectivity solution, and the rope is actually a very long fiber-optic cable.
Or the interview could be for an online eCommerce platform and the person being interviewed will most likely have to work in a huge heterogeneous codebase with all the important technical decisions already made.
otherwise the question doesn't make sense Well that is my point. I love these types of subjects, but when I'm having a beer with friends and we find a puzzle like this one and we try to take it as far as possible without going into fiction/bullshit territory.
So it could be useful to check/signal for culture fit, and in OP's case it actually worked like that OP: "We value people that love to get into this type of discussions/arguments" Interviewee: "Gosh, you guys bored me to death during the technical interview but it seems like we have similar tastes when it comes to theoretical puzzles so I'll give you another chance"
Nothing wrong with this though. It just proves that interviewing is a complex process and actual merit and success are highly subjective.
The follow-on is, if you add 6 feet and put your finger under the rope and pull up until it's tight again, how far have you raised your finger? 1ft? 10ft? 100ft? 1000 miles?
The answer to that is very difficult. There are several approaches.
I guess this type of question might serve the purpose of finding like-minded people with similar interests (in your case geometry or puzzles) but it might alienate others.
Or was it more like everybody was discussing (and explicitly or implicitly through discussion) admitting that they don't necessarily know the answer (while assumedly is an engineer in good standing on the team), and the group is working together to solve it?
Because both situations seem equally plausible based on what you wrote, and if it's the first one then I agree with your detractors below that it's messed up. If it's the second situation then I would have loved it and been excited to join your team.
It's very possible that the ambiguity of the situation is why there's such variance in reactions.
Discussion has gone off the rails here. Maybe I didn't make it clear - the puzzles were during casual conversation at lunch. Rebutting something I didn't say, is not fair.
That is not what's happening when you're interviewing me for a job position. You're not my peer. We're not having fun. There's a non-subtle implication that my ability to answer the riddle will impact whether or not I get the job. I would be very annoyed if someone asked a puzzle like this too. It's not a novel puzzle. It's mostly a gotcha where intuition meets math. I could blurt out the answer. But I would instead feel it more important to slowly reason out the answer and appear to discover it on the fly. Which is pretty bullshit. And I would think you're not very smart for thinking this is worth anyone's time.
If I didn't know the puzzle and I failed to get the job I would be mad and it would stick out as something that penalized me unfairly.
And as an interviewer, I've never been asked to report on lunch chats.
> You're not my peer. We're not having fun.
Actually, most interviewers are your peers, and they typically know that you're under interview stress and are trying to help. If you can't take a break and de-stress during lunch, you're just hurting yourself.
Every time I interviewed someone, I ALWAYS asked myself if I would want to work with this person.
Not just, can they do the job? Not just, are they technically competent? But, is this someone I would be comfortable going to, asking for help? Are they someone I can build rapport with, brainstorm new approaches and products with? Do they pass the "have a beer together" test?
Someone who explicitly has an attitude of, "You're not my peer, we're not having fun" doesn't sound like a good collaborator. Doesn't sound like someone who can be an approachable. Doesn't seem like a good mentor to newer members of the team.
Interviewing is a high stress situation where the person performing the interview ultimately has power. What you're discussing here is how well I can socially fit in - regardless of pressures/stress on my side of the table etc.
It's 100% performative - if I am an interviewee I'm showing you the professional version of myself which is positive attitude and politeness. I'm upholding a social contract.
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> Do they pass the "have a beer together" test?
I'm not here to have beers with you - I'm here to work. And, I think this is pervasive in regards to hiring. This can be incredibly discriminatory and I would appreciate you interview me on the value I can add with my labor vs. "can I have a beer with this guy?" That's weird to me, and as someone who interviews I work hard to not think this way... "Who I like" isn't necessarily who is going to perform in the role - I have to keep my personal preferences out of my professional decisions in my world... and I think that's fair.
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Idk - interviewing is not fun for most people. I defend op's "we're not peers, we're not having fun" perspective both as an interviewer, and interviewee. I think it's a reasonable stance to take as long as they're outwardly presenting as professional and polite as that's what actually matters... not "beers"
Conversely, the couple times I had those "casual" lunches as a candidate, "I'm jetlagged" was a graceful way to lie out of the question why I wasn't eating much.
Sexual innuendos from peers at the bar are one thing, sexual innuendos from interviewer are another
TBH I'd just have found it contrived and boring. I wouldn't be excited to have colleagues who couldn't just talk about normal stuff at lunch.
One reason for the lunch is to try and relax a bit and test “cultural fit”, which is more like a blind date between two people to see if there is any spark. Ideally it is a two way conversation, where the candidate and the interviewers get to judge each other.
There is a problem where cultural fit “tests” are heavily biased against minorities - for example most any sports discussion is dominated by your social class.
Enjoying brain teasers matches a particular type of geek, and the discussion likely veered or was encouraged in that direction by the candidate. It wasn’t Machiavellian, which perhaps you are more responsive to?
I absolutely don't like solving puzzles with other people. On the other hand, I do enjoy writing code on my own, solving problems (not puzzles) and then sharing the results in a readable way with others.
I do like to socialize with peers, but never playing games (I prefer to play games on the computer against NPCs).
THe reason I don't like this is there are people who've asked me ludicrous puzzle questions before and they are proxies for 'people I wouldn't want to work with'.
As with most things, it depends a lot on the history you have with those people and the psychological safety you feel, so it depends? Definitely not with someone I just met and is interviewing me for a job.
And FWIW I also don't interview anywhere there are questions like this.
At least normally when someone takes you out to the XYZ company “not part of the interview” lunch halfway through your eight hour interview loop and you chat small talk and background, there aren’t actual interview questions being thrown your way.
Imagine going to lunch and the interviewer striking up a conversation with “how many manholes do you suspect there are in New York.”
Didn't you have anything more interesting/relevant to talk about?
No, I go to work for an employer and work with my peers. My peers are not my friends in most situations. Maybe for you that is the extent of your social life so you think peers have to be friends, but you mixing the two together is your work/life balance limitation being applied to those you want to hire.
I have seen people with similar insensitivity fail to understand why people in their teams dont like them: "but I treat them as if we are peers!! I like playing on the 'you are doing it wrong'games"!!
No, we like to talk about normal stuff.
An interviewer is most certainly not a peer.
> with puzzles or tricky problems
Seeing a a middle school question as "tricky" it's a bit worrying.
You have to remember that, after about 2010, the software industry is mostly comprised of people who are after a paycheck and their actual interest in computers, STEM, and other nerd activates is kind of minimal. It came as a shock to me too when I realized that the old shibboleths of being a hacker had become largely absent in the software industry.
No, I said what I said because it's hard enough to be "on" during the coding interviews and also "on" during the culture tests, to also be "interested" in your puzzle. Wrong time, wrong place, wrong signal to send. Lunch interview (and the transport to it) is about learning about other people in a fairly non-competitive way.
d=sqrt(h(2R+h)) km/m (see https://en.wikipedia.org/wiki/Horizon#Approximation )
s=R*arccos(R/(R+h)) (see https://en.wikipedia.org/wiki/Horizon#Arc_distance )
sqrt(h(2R+h))-R*arccos(R/(R+h))-delta = 0
6 foots is about 2 meters.
sqrt(h(2*6371000+h))-6371000*arccos(6371000/(6371000+h))-2 = 0
h=306m
sqrt(h(2R+h))-R * arccos(R/(R+h))-delta/2 = 0
This can be solved for h given delta numerically, such as with a spreadsheet. Use caution here because this formula leads to a loss of significant digits from cancellation of nearly identical terms.
For example, given R = 6378000 meters and trying h = 193 meters: the first (d) term is 49618.0 meters and the second (s) term is 49617.0 meters. The difference is 1.0 meter, which is the half delta we wanted. But there's been a loss of 4 significant digits (because the first 4 digits in each value are the same: 4961). The smaller the arc distance, the smaller the angle, the worse the relative error becomes.
It's possible to analytically factor out sqrt(2hR) from both the d and s terms. In the first case,
d = sqrt(2Rh+h^2) = sqrt(2Rh) * (1+h/4R) using Taylor series for (1+h^2/2Rh)^0.5
In the second case, I can derive one formula, but the coefficients aren't the same as my numerical best fit, which is
s = sqrt(2Rh) * (1-5h/12R)
Combining the two series versions for d and s, gives us this for delta,
delta = 4h/3 * sqrt(2h/R)
Finally, solving for h given delta, take the cube root of h^3:
h^3 = (9R/32) * delta^2
Thus for a delta of 2 meters, I get height h = 192.88 meters.
It's very counter intuitive, and very easy to solve.
Years later, now a senior Engineer at our place, he admitted he had been going to give us a miss that day, until that conversation in the car.