In other words, whatever it's intended to do, one of its primary functions in practice is to screen out people who are bright, driven...and poor, working long hours and trying to keep themselves and/or their families going.
That it's a bit of a sacrifice is the point. If you're naturally smart enough this stuff comes quickly, great. If not, you're going to have to work for it - that requires discipline most people don't have.
Better put, smart and/or determined to succeed.
I once interviewed a guy- a CTO at a biotech- and he wouldn't answer the question "I have a million DNA sequences and want to count the number of occurrences of each sequence" (could be hash table, could be any number of other solutions; he just balked and exited the interview).
Only if the person can get all that right would I even consider asking something more complicated.
So usually I end up after 45 minutes finding that the candidate has more or less tapped themselves out at "make a hash table of string keys, use it to store counts" (OK for a very junior programmer) or "make a perfect minimal hash" (I help them get there if they don't know what those are) or "use a probabilistic counting filter". This is about all I need to make a determination.
https://bmcbioinformatics.biomedcentral.com/articles/10.1186...
If all you do in my interview is know that a hash table or other associative data structure is good for maintaining counts, that using a full ASCII byte to store symbols from { A G T C } is wasteful and compress the letters to 2 bits each, you can pack multiple 2 bits into bytes, and can write a function that codes and decodes such data, I'm happy and you get a pass. I'm even happy to sit there and help people through nearly all the steps of the codec. Not trying to trick anybody or select for obscure CS knowledxge.
To me the real question is, how much hinting is reasonable for the coding and decoding function? Many programmers (including senior ones) struggle to implement:
x <<= 2 # left shift the int to make room for the next item x |= pattern # or the new 2-bit item into the accumulator.
Since I never use bit munging in my day job (it's 90% python data science) should I really ding somebody for not knowing about left shift or or-assignment?
What I really don't get is why people immediately jump to trying to implement huffman coding, RLE, or lookbacks as a solution to reduce the size of the DNA string. I still wonder if how I present the question is giving everybody a fair chance to shine.
I think "key/value counts" is absolutely the correct starting answer. Anything after that is optimization. In the real world optimization comes at length through research, learning, grokking, reading, benchmarking, sleeping, mulling things over. The only way to short change that is knowing about those optimizations in advance, so might as well just ask about those algs specifically.
All that being said, I think it's an enlightening question. Thank you for sharing it! You've educated me. I've been coding a loooooooong time and didn't know about bloom counting filters specifically.
Maybe he's just been around the block a sufficient number of times to have gotten tired of the standard SV "here's a hoop, jump through it, now do it again, and again and again" ritual that it likes to call "interviewing" for some reason.
Seriously - your questions are fine for junior or mid-level roles, but beyond that, you should have more important thinks to talk about. And both of you should be able to tell if the other is a bullshitter and/or a lightweight within about 30 minutes at most (and often far quicker than that) of a normal, focused technical conversation -- without having to specifically grill the other person, or otherwise put on the pretension that you're one whose bona fides are established beyond question, and they're the one who needs to jump through a sequence of hoops to prove that they are worthy of your time and attention.
Just cut the crap, get down to brass tacks, and talk what needs to be done as if they're a peer. That's all you have to do.
With Leetcode, you have to retake the test multiple times every few years when you change jobs for each company you apply to.
Leetcode would be a lot more tolerable if it was administered more like the bar exam or like medical exams. Whatever happened to DRY?
Even having to pass such a test on a very aggressive set schedule—say, every 5 years—but only at those set times, would be better—for developers. Not for the companies hiring them.
Which means... Always. Be. Leetcoding. Do the bare minimum at your job and then do LC the rest of the time. Because your job is just your job, but your career is LC. These companies don't yet realize they are optimizing for mercenaries that have no loyalty to the code nor the company.
On a slight tangent, some of the people over on Blind would sell their own mother for a tiny bump in TC. That mentality used to be limited to Wall St. or maybe Big 4 accounting firms, etc. But now it's the whole tech industry. I remember having a software job was a lot more fun, back around 2007ish. That culture is so foreign to me now.
Whether you realize it or not, you're advocating for keeping people who aren't already mid-to-upper-middle-class (among others) out of these kinds of tech companies. Anything that's designed to make you work hard extra, outside of work to learn separate skills just to pass interviews is guaranteed to make it disproportionately harder for people who are, for whatever reason, unable in practice to devote many hours of their free time to fairly complex technical studying.
No matter how "disciplined" they are, people already working 80 hours/week just to put food on the table don't have the luxury to be doing that. No matter how "smart and/or determined to succeed" they are, people raising 2 kids by themselves would be irresponsible to be doing that.
Now, maybe you think that kind of person should be denied an opportunity to join the super-1337 hackaz' club that is FAANG or whatever. Personally, I think that kind of classist gatekeeping is disgusting.
Ah, you're talking about those programming jobs that never require thinking about algorithms?
I've been working as a programmer—largely PHP, Java, Objective-C, and Swift—for over 20 years now, and never, in my work, have I been asked to invert a binary tree, reverse a singly-linked list, or any similarly contrived scenario.
There's a huge difference between "thinking about algorithms" in the most general sense of that phrase (which means basically any programmer who does any of their own design work) and in the sense of the particular "algorithms" that we learned in CS classes and are featured in Leetcode problems.
Search engine: read material about the heart of the problem from domain experts, try different approaches and then decide.
Leet Code exercises are a blight on our industry.
If you want a shibboleth just say so.
Being able to quickly invert a binary tree and that kind of nonsense belongs in library code (at best). It's not something that the average developer should ever need to worry about the actual implementation of, let alone have to implement from scratch in under 30 minutes.