[nugator]

Was it necessary to know on the top of your head without Googling what a binary tree is for the position the candidate applied for? I've been a developer for 12 years and I've never had the use for that. Computer science is a VERY large field and being good at everything is impossible.

Asking the right questions at interviews are crucial for finding the right people. If a candidate for a programming job knows binary trees but doesn't listen to other peoples views I would say he's less worth to us than a listener that easily learns new concepts but is currently not familiar with binary trees.

BTW, leaving a candidate in tears is not professional recruiting. Please let someone with more people skills accompany you to your interviews, you might leave people with scars that takes years to heal.

[AnimalMuppet]

I've been a developer for 30 years, and I haven't ever had a need for it, either - but I still know what one is. I expect that you do, too.

[nugator]

I came across it when studying computer science 20 years ago, yes. Heard about it after that but never directly needed the knowledge.

I'm sure it's used under the hood in a lot of code I write and have written but so is XOR, manual memory management and a bunch of other lower level implementations that I don't need to spend time on when developing on a higher abstraction level.

Not sure why you would expect all programmers to know about binary trees specifically.

[Retra]

Binary trees are the simplest kind of nontrivial tree, and trees are used extensively in programming. Most computer problems are solved using trees of one kind or another.

[ascorbic]

If you've never needed to know it, what is its value for finding a good candidate? A lot of these questions are basically testing whether you did a CS degree. If you're self taught, you might be just as good a coder, but have never had reason to learn what a binary tree is or how to implement quicksort, or whatever similar puzzle.

[quickthrower2]

It's a nice way to filter out people who can code and basically do the job, but didn't have the financial resources to get a CS education, and weren't lucky enough when researching to see that his is an interview question. Although at least they'll know for next time.