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https://blog.usejournal.com/rethinking-how-we-interview-in-microsofts-developer-division-8f404cfd075a https://blog.usejournal.com/rethinking-how-we-interview-in
by sxp 8y ago
https://blog.usejournal.com/rethinking-how-we-interview-in-microsofts-developer-division-8f404cfd075a https://blog.usejournal.com/rethinking-how-we-interview-in-m... is the original post by a PM at Microsoft. It doesn't have any useful information about a pure technical interview for software engineering.
>(Note: I started at Microsoft when we were still asking questions about why manhole covers were round, how many ping pong balls would fill a 747, and how to reverse a linked list. In 20 years here, I’ve yet to have to write the code to reverse a linked list (copy-paste anyone?) or fill a 747 with any kind of ball.)
The manhole cover question is actually a valid industrial design or UX question even if it's not appropriate to ask for software interviews. The linked-list question is the equivalent of Fizzbuzz for data structures. And the 747 question is a valid Fermi problem. The exact number doesn't matter but the steps required to estimate the answer are similar to other estimation problems when mapping out a business strategy and trying to determine if it's profitable. Or maybe the company is interested in salvaging sunken planes: https://www.iusmentis.com/patents/priorart/donaldduck/ https://www.iusmentis.com/patents/priorart/donaldduck/
- akhilcacharya 8y agoI've interviewed at MS a couple of times and I've never had a question as easy as "reverse a linked list".
- WrtCdEvrydy 8y agoIsn't the round manhole covers just to make sure they can't fall in?
- Retric 8y agoIt’s actually several things. It’s stronger, cheaper, rolls, lighter, no need for alignment etc. You can make sure any shape does not fall in, but strength to weight ratio is important as you want people to open them with hand tools while supporting dump trucks. PS: At ~250 lb you can see why a less optimal shape might be a problem.
- m0zg 8y agoIt's also utterly irrelevant to the software engineering profession.
- deleted 8y ago[deleted]
- twodave 8y agoLess raw materials to produce, easier to transport by rolling, easier to place onto the manhole, easier to stack when transporting/storing in bulk, etc
- JustSomeNobody 8y agoFlies like a frisbee when Superman throws it...
- werkjohann 8y agoOr better - Elastigirl! https://twitter.com/SamuelGavin/status/1008636415524171776 https://twitter.com/SamuelGavin/status/1008636415524171776
- antaviana 8y agoAccording to the Wikipedia [1] Reasons for the shape might include: * A round manhole cover cannot fall through its circular opening, whereas a square manhole cover might fall in if it were inserted diagonally in the hole. The existence of a "lip" holding up the lid means that the underlying hole is smaller than the cover, so that other shapes might suffice. (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture.) * Round tubes are the strongest and most material-efficient shape against the compression of the earth around them. * A round manhole cover of a given diameter has a smaller surface area than a square cover of the same width, thus less material is needed to cast the manhole cover, meaning lower cost. * The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe. * Circular covers do not need to be rotated to align with the manhole. * A round manhole cover can be more easily moved by being rolled. * A round manhole cover can be easily locked in place with a quarter turn (as is done in countries like France), which makes them hard to open without a special tool. Lockable covers do not have to be made as heavy, because traffic passing over them cannot lift them up by suction. [1] https://en.wikipedia.org/wiki/Manhole_cover https://en.wikipedia.org/wiki/Manhole_cover
- walshemj 8y agoIronically all the utility covers I see in the UK are square. I also think the casting argument is a good one and its a lot easier to cast a round object than a square one (its to do with how molten metal flows)
- derefr 8y agoDon't forget also: round manhole covers are a Schelling point. Making a manhole cover round is one of the first intuitive shapes you'd think to make them (along with squares and rectangles); and so you'd guess, as a construction company gearing up to sell the concept of concrete manholes with removable iron-plate covers to a municipality (back in the 1800s or whenever we first got them) that what the municipality will ask you to make is round manhole covers. So you provisionally set up your tooling for round manhole covers, and build a few for the demo. And the municipality assumes you're the expert about good manhole-cover shapes, and so just goes with the flow, rather than trying to figure out the best shape themselves. So you end up with "the first intuitive thing that worked" spreading via network/"system compatibility" effects. Same with road widths; same with screw drives.
- FigBug 8y agoThe covers are round because the holes are round. :P
- commandlinefan 8y agoYou’re hired!
- commandlinefan 8y agoThat’s exactly why they’ve given up the brain teaser questions - all it checks is whether somebody’s told you the answer before.
- coralreef 8y agoGoogle stopped asking brainteaser questions like that because they found no correlation in its hiring usefulness.
- kerng 8y agoI think it's true for majority of questions (apparently leetcoding is the new thing at Google and also FB). IMHO interning for a few weeks is the best for both sides - unfortunately it doesnt scale.
- kabdib 8y agoInterning "for a few weeks" means that you miss out on candidates who already have perfectly good jobs. These are often the folks that you are trying to hire. So imagine how a candidate reacts to, "Well, while we know you're happy where you are, what would you think about quitting your current job so you can try out a position at our company for a few weeks?" (Note that candidates can't use vacation time just to do a try-out, for legal reasons, and may be reluctant to use up all their vacation time in any event). Having a trial period puts all the risk on the candidate, and guarantees you're filtering out people that you'd otherwise want.
- BurningFrog 8y agoI'll be the obligatory ex Googler claiming Google never did ask brainteaser questions, or at least they were long gone by 2006.
- 13of40 8y agoPuzzle questions were definitely against company policy and at least ones unrelated to coding were rare by that time at Microsoft, too.
- seanmcdirmid 8y agoWouldn’t the current niche clever dynamic programming problems google asks you to work out on a whiteboard be classified as brain teasers? Sure, it’s much easier to prep for via the cracking code interview book, but is still not something you would encounter in the wild.
- watwut 8y agoManhole question is bad, because around half manholes im real world are squared. So the correct answer is that they are not in fact round and square works perfectly fine. Of course I know right answer, but it has zero to do with me being smart and a lot to do with me being in right culture and thus having heard about it before. Which is exactly what it test along with other brain teasers - have you encountered this sort of question before?
- kerng 8y agoHaha. That was exactly what I was thinking! I have yet to see a round one! Lol
- smsm42 8y agoThe correct question, obviously, would be "why in some places they make manhole covers round and which advantages and disadvantages over square ones they have?" Which, as any good question does, already contains part of the answer.
- chrisbennet 8y agoData point: There are triangular manhole covers on my street.
- 13of40 8y agoThere was a linked list interview question going around back then that went: In constant time, without allocating memory, given a pointer to the first element of a linked list, how can you tell if it eventually ends in a null or if it loops back on itself at any point? I actually ended up implementing the solution while tracking down a hang in a DCOM service I was working on...
- billsix 8y agoIn constant time? O(1)?
- Matthias247 8y agoIsn’t that normally the 2 pointers (tortoise/hare) thing? If yes then I agree it’s not constant time. I personally hate this kind of interview question. It’s one that is easily answerable when one heard the exact question before (in training for interviews). But super hard to answer if not. And it even does not have big applications in practice - in 20years of programming, I never encountered a problem like this. In the end the question just wastes time on both sides and won’t really tell a lot about the candidate.
- lawn 8y agoHe meant constant memory. It's to invalidate solutions marking items visited. I too got this question at an interview once, and failed. For fun I asked everyone at work and predictably nobody came close to figuring it out.
- 13of40 8y agoNo, I meant O(n) but used the wrong word for it. Marking items visited can actually work, because on any(?) modern OS the memory for the elements in the list would be allocated at even addresses, meaning the low order bit of the Next pointer is always zero and can be reused as a marker.
- 8y ago
- JamesBarney 8y agoI don't think the 747 problem is very predictive of how well someone can map out a business strategy. I think a better question might be, "tell me how you've mapped out a business strategy in the past, and what are the strategies you've used to determine how profitable it would be".
- cm2187 8y agoBut the real question is whether you can fill a 747 with internal policies and procedures!
- m0zg 8y ago^ this person is probably a PM at Microsoft. :-) When I worked there (over a decade ago) the place was so regimented you couldn't rip a fart without having to write a specification and estimating a schedule.
- yarrel 8y agoThe manhole and 747 questions test for obedience and bikeshedding, not problem solving. Likewise the linked list reversal question tests for lack of planning and critical thinking. These anti-skills will have been used quite regularly at Microsoft.
- DATACOMMANDER 8y agoHow does being able to reverse a linked list suggest that one lacks the ability to think critically?