Do you spend 5-10 minutes googling and reading about the Linear Search algorithm[0] every time you iterate through a list and have a conditional to do something if an element matches some criterion? BFS, or a generic graph search (could be BFS, DFS...), is essentially just linear search except each element can have 0-n direct next elements, instead of 0 or 1. It's not this hard thing that never comes up...

Indirection is great in this trade, a lot of what I "know" is just an index key/search strategy to go look it up again. But a lot of what I "know" I know directly. According to this old paper[1], for many fields including software you need to directly know about 70k±20k random things in the field to be in the running for expert status. Proficiency is also related to how many things you know directly. Thus you can't do an index lookup for everything unless you have no constraints on time and/or don't care about improving your level of expertise.

[0] https://en.wikipedia.org/wiki/Linear_search

[1] https://apps.dtic.mil/dtic/tr/fulltext/u2/a219064.pdf

You won't be able to Google it, because you never ever asked to BFS by name.

You will be asked to find the biggest file in folder structure, find largest modúle in dependency tree or the person in data structure that has no department and thus caused null pointer exception.

You also won't google it, because it is simple and ylnormal programer don't need google for this.

No problem will present in such an easy way as "oh just apply BFS". As part of a big project you often have to use many different algorithms for sub parts, often modify them to suit constraints.

I think the HN crowd is heavily inclined to web apps and also front end. I can't tell you how important fundamental CS knowledge is for backend. I bet you can't use a library or API for how caches work or when paging happens. Knowing these things makes you a well rounded engineer ready to tackle different problems. I can trust you to write a mobile app or work on some part of a self driving car because you have the building blocks to do so. Most of the comments in such threads have no interest in interesting and diverse jobs because "why bother, when will I use this". To any new grad, yes the interviews can be better but please spend time on these things at school. They are an investment in your career's stock.

I was recently asked to identify pages in our 10 million line application that use a certain piece of business logic. It involved parsing the page and their nested subcontrols into a tree with by doing a modified BFS on the linked files, doing a modifed BFS on the tree to identify the related code behinds, parsing the C# from the codebehinds into a tree, and traversing the C# tree (again with a modified BFS) to find if the code path was hit.

These questions come up all the time. You just need to be proficient enough with algorithms to identify them.

No but I can give a few examples where I refactored code from these antique pointer-based trees (inspired by classic CS books, half century old now) towards something more cache friendly, and improved performance by an order of magnitude.

There is no "deep understanding" of BFS. All it is is look at your siblings before your children.

I wouldn't hire an electrical engineer who complained that he shouldn't have to know Ohm's Law, either.

uh, I thoroughly search each room, starting at the left corner and recursively iterating via a hilbert curve.

doesn't everybody?

I would certainly probe deeper if given that as evidence for a strong grasp on the utility of BFS.

That's definitely now how I do it. I go deeper into each room, the depth (as well as the order) being decided by (roughly) how much time I spend in each room every day. E.g., Go waay deeper in living room, less so in bedroom, lesser still in bath room and so on :-). This I'd imagine is "more" common sense than than an un-informed BFS?

This is actually not how I search. After the first search, if I am getting frustrated, I do what I was told when I was a child: "start picking up stuff until you find it". So I guess that's kind of a depth first search after going over the top layer.

I'd use an indexed search and remote activate the beeper in the key chain

I don't think I've ever lost my car keys so does that make me a NULL pointer!

Watch me get downvoted to hell though :)

There's a reason such tweets resonate so well:

1. Creator of top software project can't pass whiteboard interviews.

2. I can't pass whiteboard interviews.

Therefore, they are stupid for not hiring me.

It strokes everyone's inner narcissist--why spend the hours on leetcode, they are stupid anyway.

i mean if had to choose between no graph theory vs no ruby on rails...i would probably go with no ruby on rails

I wouldn't hire someone who cares so little about getting a job that he didn't spend the most basic amount of time studying for obvious questions that he was of course expected to be asked.

Such a situation would show me that he either does not care about getting the job, or is so arogent that he automatically expected that people who throw job offers at him.

That shows that this person has horrible personality problems and that I would not want to work with him, no matter how much he has accomplished in his life.

BFS is "Breadth first search". One tree you would do this on is a BST or "Binary Search Tree". Probably OP got the acronyms mixed up.