Or even just when would you use a binary tree? Figuring out which data structure is appropriate for the problem at hand is the hard part, how to implement operations on the data structure is easy in comparison, you can just Google it.

That seems to be the wrong question though. It seems to be jeopardy style "question". You are not asking which data structure is appropriate for a problem.

Here is the answer, but what is the problem it solves.

Never in my live have I sat down and said: I don't know what problem is I need to solve, but I know the solution is a binary tree.

Uhhhh... It eliminates competent, skilled people who don't have the time to memorize the latest cargo cult trends in hiring. Look in the article for a glaring example.

"Invert a binary tree" is actually considered an easy problem to test your basic knowledge of how trees work and tree traversal.

So would simply printing out a tree, and at least that's something a person might actually do.

Tree "inversion" doesn't even make any sense and at this point I'm convinced that the cargo cult is choosing it because it's the extent of their own understanding of trees and somehow sounds extra technical to them.

I agree completely it eliminates a huge swathe of people, mostly experienced and older people. FAANG employees, ime, are biased towards childless / single people with privileged backgrounds.

Tree inversion sounds weird when you hear it phrased like that, but in an interview it would be explained with an example (just swap the left and right children recursively).

It also seems to neatly split people into camps who think "this is trivial, and totally reasonable to expect somebody to answer, even if it's a little contrived", vs those who think "this is not practical, and you'd only know the answer if you'd already practiced it, so it's not fair to ask".

> It eliminates competent, skilled people who don't have the time to memorize the latest cargo cult trends in hiring

But given that you already acknowledged that it's pretty trivial, why would memorization be necessary for a competant person?

What's easier?

You usually aren't coding FizzBuzz in production code either

I would say you're constantly coding FizzBuzz. Looping, modulus arithmetic, and conditionals are all over the code I've written. At least with FizzBuzz you have a test of a person's ability to understand a task, break it down, and make sure the logic is consistent. With tree "inversion" it's not even a sensical request, it's utterly useless, and there are countless more interesting and practical ways to test understanding of recursion and trees. Knowledge that, I would bet, isn't even relevant for 90% of programmers, and if tree traversal were relevant then you'd probably want to jump to way more difficult questions (I'm thinking of the Facebook graph, for example).

I agree with the other commenter that it would make far more sense to ask questions like "you need to process data of this type, what provided data structure (e.g. C++'s STL) would you choose?"

Every (recently with raft protocol) multi master distributed system out there interacts with Zookeeper for assigning leader and maintain configuration.

Do you know how the syntax or api calls look like ? They are node path in a tree. You want to store something ? That's a tree path again. You want to listen to some change ? It's tree path again.

As I said, most people are ignorant here and don't do "true" computer science engineering in daily life.

Most devs simply convert business logic into bunch of apis + adhoc implementation.

Did you ever work at a banking firm ? I've read their codebase - they are structured as trees, every damn thing is tree. It's a headache to navigate, code, heck even the objects are literal trees.

As I said, people are ignorant and think world revolves around them.

Honestly? Because that's harder.

The swapping question is basically a softball / FizzBuzz-style question to test the most basic familiarity with data structures, pointers/references, and recursion.