TBH that's another argument I don't really get. Almost everyone agrees that basic CS knowledge trumps specific technology knowledge (I'd rather hire someone with strong CS fundamentals that didn't use Java before than someone who is a "Spring Boot expert" but lacks basic CS knowledge, even if I actually use Spring Boot right now).
But then, why complain that you don't do that in your work? Surely you need to traverse data structures from time to time, yeah it won't be the exotic tree traversal that I'd ask you to write but that's exactly the point - to test that you can be put in a novel situation that can't be directly-pasted from StackOverflow and you're able to write a recursive function that takes _a little bit_ of skill).
The hidden test case is opportunity for discussion during actual interview. And this answers your "what's stopping them" question, too - regardless of problem, I can tweak the input slightly so that your solution doesn't work - and more often than not, I don't even tweak the input, I just provide an additional testcase where your solution doesn't work. If you can quickly fix it ("oh, yeah, I forgot that URLs may have a fragment appended to it, let me quickly adjust my log-parsing condition") then it's awesome, it's exactly the signal I'm looking for, and we can go on to discuss system design and your relevant experience (but honestly, at that point my mind is likely ~80% made up, from CV + how you explain/modify your hackerrank solution).
TBH that's another argument I don't really get. Almost everyone agrees that basic CS knowledge trumps specific technology knowledge (I'd rather hire someone with strong CS fundamentals that didn't use Java before than someone who is a "Spring Boot expert" but lacks basic CS knowledge, even if I actually use Spring Boot right now).
But then, why complain that you don't do that in your work? Surely you need to traverse data structures from time to time, yeah it won't be the exotic tree traversal that I'd ask you to write but that's exactly the point - to test that you can be put in a novel situation that can't be directly-pasted from StackOverflow and you're able to write a recursive function that takes _a little bit_ of skill).
The hidden test case is opportunity for discussion during actual interview. And this answers your "what's stopping them" question, too - regardless of problem, I can tweak the input slightly so that your solution doesn't work - and more often than not, I don't even tweak the input, I just provide an additional testcase where your solution doesn't work. If you can quickly fix it ("oh, yeah, I forgot that URLs may have a fragment appended to it, let me quickly adjust my log-parsing condition") then it's awesome, it's exactly the signal I'm looking for, and we can go on to discuss system design and your relevant experience (but honestly, at that point my mind is likely ~80% made up, from CV + how you explain/modify your hackerrank solution).