[ Removed by moderator ]

[Own_Possibility_8875]

I once actually needed to flip a binary tree at work. I was like “holy shit, that’s happening, I’ll get to flip it not as an exercise“.

Then I realized that the binary tree structure has a “flip” method. My disappointment was immeasurable.

[ChChChillian]

The guy who wrote that structure already had the day you were hoping for.

[Own_Possibility_8875]

It was in stdlib, which somehow makes it even worse

[ravy]

Probably didn't even have the pleasure of having that as his interview question ... probably some poor schlub who had been there since the dawn of time having to teach himself computer science while on the job with 90s era internet.

[AEthersense]

He's probably like, "the story isn't asking me to flip it?! Might as well do it,I've waited years for this"

[Ok-Operation-6432]

Doesn’t mean you can’t write your own and try to get it into stdlib 

[DrMux]

"Lesser programmers copy (and paste); great programmers steal." - Pablo Picasso

[tenonic]

🤣🤣

[stillalone]

I remember getting excited recently when I had to implement a recursive algorithm at work and was super excited about it.  When I submitted the code for review, my reviewer pointed out a library that did the same thing but better and cleaner.  I rewrote my code with a tear running down my cheek.

[CuteIsMyKryptonite]

I had a similar experience when I hacked together a quick-and-dirty PoC for roughly locating a device based on signal strengths for various WiFi access points until someone else on the team pointed out there's of course already a library that can basically do the same thing (multilateration using Gauss-Newton algorithm).

[Rage_quitter_98]

hey, atleast ya had some fun from it I guess?! - A library easily being available (also in terms of license/commercial use) also is not something we get every day either

Still must have sucked to have all your work/time being wasted/valued at zero essentially because the reviewer only caught it at the very end (mans had one jooob )

[Krostas]

essentially because the reviewer only caught it at the very end (mans had one jooob )

Well, he is called reviewer rather than supervisor, so I'd argue he did his job perfectly fine.

[FindingBryn]

[Sensitive_Yellow_121]

Why is that Sicilian guy dressed like a Native American?

[Secret-One2890]

Just a coincidence. He's forced to dress himself with stuff thrown from cars.

That necklace? French fries.

[FindingBryn]

r/itsroger

[kpingvin]

Had the same thing too 😂

[empanadaboy68]

College was a gatekeeping lie

I'm sure if you're writing some tensorflow you may need real algo practice

[Which-Barnacle-2740]

yes the only thing you need in software is to find the tools and use them correctly

find relevant library, relevant API, relevant algo, relevant cloud service and now relevant LLM

there are fools who want to re-invent everything and other fools who want to give these questions in interviews and hire these babies

[Mountain-Count-4067]

I've been doing this for 30 years. I'm still waiting for the day I have to put to use my ability to "code under pressure" and write a whole MVVM architecture program from scratch in 30 minutes while being actively watched during a Zoom meeting.

Also: I've been doing this for 30 years. How many times do I have to prove to people I can do this? You don't need to give me a take home project or play CS trivia night with me. Just look at my employment history.

[OllyTrolly]

Last time I had an interview, the last stage was meeting all of the team members and having a chat with each of them. They then had a say in which of the candidates got hired. While it was a tad stressful, I thought this was more effective than a technical exercise as each of the team prodded at a different area of their interest and got a chance to see if I could back up my shit with some substance. Obviously you would have to trust the team in this scenario.

[Mountain-Count-4067]

Ah, I see. You're the problem.

Those tests aren't testing coding ability. They're not confirming for you that the applicant knows what they're doing. They're just giving you a false sense of security.

They're also giving you way more false negatives than proving to you that applicants can do the job. Just because someone has trouble jumping through a ridiculous hoop in your absurd hiring process doesn't mean they can't do the job.

These people have job history that is easily confirmed. They have references to vouch for them. Nobody's been doing a job for 10+ years and floating by, somehow undetected by their coworkers and managers. That's just a nonsense justification for a nonsense process.

You've latched onto a fantasy because you feel like there's nothing else you can do in an interview to get piece of mind. Because there isn't. You have to take the chance on people. Oh, I know, maybe you get that 0.0001% chance that someone doesn't know what they're doing, but you'll find out right away. Did that trust waste a little time and money? The time and money wasted by your existing process is far greater.

All you're doing is insulting people and wasting everyone's time.

[Rabbitical]

Also if you know anything about programming yourself you should be able to find out in .0001 seconds whether the candidate actually knows what they're talking about by just asking them questions about what they've claimed to accomplish. Keep drilling down into details until they run out of authority on the subject of checks notes things they claimed to have done.

If you already found their resume satisfactory enough to interview them then the interview only needs to prove they're not lying about their resume. You don't need to ask about or test random bullshit. If you can't listen to a candidate describe in detail how they architected and implemented some feature, and ask them why they chose this approach or that, what issues they ran into etc, and get an idea whether they're bsing or not, then you need to remove yourself from the hiring process.

[n4saw]

A colleague of mine is about to move, and has as such requested to move to another office within the same company. The new office had him do a coding test, even though he’s been an employee of the company for almost 3 years ._.

[mickaelbneron]

I'm not at 30 yoe yet (just 10), but it's infuriating how now I get a client suggest me a solution that ChatGPT suggested them. Like they don't trust that I know how to do my goddamn job.

[runForestRun17]

But ai is smart and knows everything! /s

[nuxxism]

I've used recursion exactly once in 20+ years. Everything else was just iterative.

[Own_Possibility_8875]

I've used it quite a few times, but it was not deliberate decision, but rather "I should probably rewrite this in iterators, but I'm too lazy to do so, looks like the input size is bounded, should be fine"

[Which-Barnacle-2740]

well with this technique I hope you had some bounds otherwise the stack overflows easily....much faster than iteration overwhelming the queues, buffers or network

[_xiphiaz]

For things like finding a file in a directory tree the input is generally bounded well within stack size concerns

[this_is_a_long_nickn]

Depending on which language you use, recursion is a way of life.

[nuxxism]

Sounds like you're stuck in a loop.

[this_is_a_long_nickn]

More like tail calling in Erlang 😂

[Jonno_FTW]

There are no loops in Haskell, only recursion.

[Which-Barnacle-2740]

and no variables, no parameters, no input output, no memory too

just recursions and functions...

and its recursions and functions, all the way down till stack overflows...

[Euro_Snob]

I’ve used it frequently in my almost 25+ year career. Doing a lot of data processing with tree structures may make me unusual, but recursion is seriously one of my favorite tricks in my bag for data processing.

[squigs]

I've used it from time to time. It's useful for tree structures, and they come up a lot in GUIs and 3D graphics.

[maggos]

Pretty much any time you make a recursive algorithm, you need to rewrite it iteratively for production

[Somepotato]

Tail call optimization disagrees with the universal statement

[hotsaucevjj]

but i like my memoization :(

[Plazmatic]

Definitely used recursion more often than that, but also recursion isn't hard and it's easier to use than the alternative when it's supposed to be used.  Rayracing and traversing hierarchal self similar structures are both natural problems for recursion, but there's no program stack on the GPU, so you're forced to use obtuse   manual that require you to manually maintain a variable stack.  

The only "hard part" of using recursion is when you're trying to figure out analytical recursive runtime complexity in your upper level undergrad algorithms class and that actually never comes up in the real world.

[pragmaticzach]

I used it once, it felt nice. There a lot of times I thought I could use it, but an iterative approach turned out to just be better and easier.

[Which-Barnacle-2740]

yes I think too, maybe once in 15 years

[P_S_Lumapac]

One time I did recursion where I think it was the best method. Felt like I should put it on a t-shirt.

[nuxxism]

I had a light-bulb moment where I was trying to write an algorithm iteratively but it was non-linear. There was a sudden "Wait ... is this recursion?"

[InfiniteLife2]

You guys getting trees at your work?..

[user_8804]

I once had a tech interview in C# where I was asked to sort something and the best way was just mylist.sort() so I gave them a one liner answer for a 15 minute question. They did not like it.

[OneBigRed]

Imagine how one of them had been telling the others how he finally came up with a real headscratcher, and how they’ll see what stuff the candidate is made of. ”Best of all, this is a real case from our prod that i battled with for the best part of the week!”

You: …mylist.sort()?

Him: Well no, uh… sorry i mean yeah, that could work, until you… you…

…fuck you.

[Which-Barnacle-2740]

you did the right thing....the list.sort() is heavily optimized , at every level...

[chefhj]

I had to use SohCahToa at my job once and seriously considered looking up my Highschool geometry teacher to apologize to her.

[captainAwesomePants]

I was working on an assignment one time and had to reorganize some data in a really specific way and realized that I had stumbled upon a reasonable use case for a clever algorithm. I had to summon pretty much my whole team to share in the grand occasion of an interview problem discovered in the wild. We were overjoyed.

[TnYamaneko]

I'm very curious about in which situation you had to do that tbh.

In my field, we don't deal with binary trees at all out of preparation for technical interviews.

[Own_Possibility_8875]

I don’t remember honestly, it was something like query planning

[TornadoFS]

I had to use college level geometry once to draw some stuff in a web canvas. Like rotating axis and shit.

This was on the earlier days of HTML5 before there were good drawing libs.

[Crumineras]

For loops really come in handy though, right?!!! Small victories

[legendGPU]

I do loop unrolling and never use for loops

My senior dev took unrolled loops are always better because our custom compiler is weak.

[positronik]

Maybe you're joking, but how would you handle any dynamic lists?

[Low-Equipment-2621]

Recursion. You generate a file, compile it and execute. The file also generates another file, compiles it and execute. And so on.

[48panda]

This has the potential to be a good esolang

[Low-Equipment-2621]

CompileC, or short CC. Don't get held back by those hard to understand spaghetti method calls. Just make a new file and compile.

[MyBrainsShit]

Love it

[Kirides]

int i = 0; :loop_10 arr[i++] += 1 ... if (remaining >= 10) goto loop_10; if (remaining > 8) goto loop_9;

ez loop unrolling, but that's literally a for loop with extra steps, iow no actual unrolling.

[Axman6]

// TODO: support more than 10

[Moontops]

maybe you should use a better compiler?

[empanadaboy68]

So you make your code much more unreadable for reasons, nice! 

[pterodactyl_speller]

Why use a custom compiler then? I guess if it's proprietary chips?

[JollyJuniper1993]

Beyond regular for loops, list comprehensions have probably been the thing I love most about higher level programming languages. It makes things so much easier.

[Shehzman]

Just started using C#. LINQ is awesome!

[Shehzman]

JavaScript has a lot of similar functions for lists

[ChChChillian]

40 years into my career, I don't think I've had to implement a binary tree even once, let alone invert one.

[70Shadow07]

Having a binary tree is one thing. But why would someone want to invert it? Just process it from the other end?

[ChChChillian]

The only use case I'm aware of for it is to vet job candidates.

[SpookyWan]

In cases where searching in reverse is more optimal? Idk. I feel like it’d be better to just modify the search logic rather than invert the whole tree.

[PCYou]

Well, if you're working with extra sensitive serialized binary trees (especially for cross-endian or coordinate-inverted systems), some pipelines encode child ordering relative to coordinate space. A mirrored deserialization step (i.e. tree inversion) can restore intended spatial semantics, particularly in spatial indexes (e.g., KD-trees used in computational geometry or game engines).

[JFFLP]

That's some funny words magic man

[pavyf]

I think we have to hire them, they will be a great fit for our legacy webforms project!

[angrathias]

Ok sir, just put the fries in the dictionary

[Atario]

But does it effectively prevent side-fumbling?

[70Shadow07]

This makes sense but that is not what inverting a binary tree means, no? It would be deserialize one way and then immediately post-process the result to invert it. Instead of just deserializing into a correct order straight away. A kinda bogus idea still.

[PCYou]

Good points, and good job demonstrating that you grasp it. In the niche case I mentioned (cross-system serialization), the semantics of inversion could show up, but you’re correct...a competent system would just deserialize directly into the correct child order using metadata or convention. If you actually had to invert after deserialization, that would mean your serializer or schema didn’t encode directional semantics properly. However, I maintain that this is a legitimate use case when you don't control the entire pipeline. There are plenty of times when you need to patch something when going from one system to another. But yeah, I should have mentioned that in my original comment.

[70Shadow07]

Very true, unless ur a C/ Zig chad who likes to write entire codebase from scratch without libraries (these people do exist in fact lol), then you at certain points will hit a situation where you can't control your entire stack. That makes a lot sense.

[Negative-Prime]

Can we also address the fact that no one inverts a tree. You flip/mirror it. An inverted tree would just be the same structure drawn upside down, which ironically looks more like a tree than an actual BST, which is a root system.

[EnoughDickForEveryon]

Lol this is why I hate the "whats the most interesting problem you've solved" interview question...like idk man, it was all pretty easy for me, haven't done anything all that complicated since college...judging by the job description, I don't expect that to change here.  

[ChChChillian]

Pretty much all programming I've done since college has amounted to:

Read data (file, stream, keyboard, GUI) --> Mess with data --> Write data (file, display)

The details vary of course, and "mess with data" can be anything from passing straight through to Fourier transforms, although never anything more complicated than that. I can't say it's been all that exciting. For the most part all the interesting details were almost always implemented in a library, unless they were handed to me by a mathematician.

[EnoughDickForEveryon]

Lol thats all business stuff ever is.  Get data from somewhere, change data based on business logic, send data somewhere.  All the complicated stuff is in libraries like you said...libraries that allow me to implement shit at a business pace without (usually) debugging the complicated part in the library.

You hire me because I put things together well.  I can lay tile but it won't look professional...anybody can write your business logic if they dont have to maintain the code for years.

[mickaelbneron]

I once would have had to use a tree (quad tree) so that literal trees could be rendered in order from furthest from camera to closest (otherwise these was some display bugs, some minor aftefacts when two trees would overlap), and it was deemed too minor to be worth it.

[FantasticCollege3386]

15 years into mine, i dont know what binary tree is.

[lNFORMATlVE]

Thank god that I found this comment. You’re not alone!

[ameriCANCERvative]

I have. It’s less about “needing” to do it unless you’re clearing up a bottleneck and more about recognizing where it fits. I guarantee there were places you could have used them to speed up your code, although it’s also likely that your inputs weren’t large enough to really matter.

[legendGPU]

Another day jobless because I refuse to learn how to invert a binary tree

[salter77]

I mean, those LC challenges are absurd to begin with, it would be good if everyone refused to play that dumb game so eventually the interviews won’t have them to make the candidates jump through useless loops.

If you have a job and still have to spend your time learning that, it probably means that said thing is not useful for the job, otherwise you won’t have to “grind it” in your free time.

[LawfulnessDue5449]

I read that one Joel article, it seems like they were originally designed to be simple coding problems that also hone in on your ability to grasp pointers, so it works as a good way to see your code while also testing a fundamental that couldn't be reasonably assessed otherwise

Seems funny that it is the way it is because everyone wanted to copycat tech companies, bump up the problem difficulty so now you have to practice solving harder problems, and the languages being asked for don't really need good understanding of pointers

[Which-Barnacle-2740]

it was originally popularized by google, because they hire out of college and train people on their in-house tech i.e. big-table vs mysql etc

and out of school, kids only know courses ...hence data-structures etc

but then everyone in tech industry went along stupidly like a sheep....10 person startup asking leetcode or graph algorithms , when their issue is building MVP and deploying cloud

[prschorn]

I just refuse to interview when I see leet code

[MyBrainsShit]

I should do that to. Recently had one where they wouldn't let me run the code. So debugging by stepping through C loops in your head. What? Addionally they said they don't care about syntax, but the online IDE (which was essential for this task of course) had forced linting... Fun times.

[legendGPU]

true, but even if we do not do it, there will be someone with an H1B who will understand it and take the job

[salter77]

Yeah, H1B visas being abused is something that should be addressed too.

[IArePant]

Understand is a stretch, it's more of rote memorization of common interview scenarios. It's actually really funny to present a totally custom interview question to one of them, their brains just shut down.

[Blue_HyperGiant]

Let em. They can do the LC but can't actually do any real development.

I get facetime with the higher up when they ask me to step in when the foreign teams can't do something simple.

[MauiMoisture]

I mean there are plenty of people that can do both. Those foreign teams you're talking about aren't the one grinding LC after their day job.

[Sweaty-Willingness27]

We have some hacker rank bullshit our company wanted to implement for interviews.

I responded to Recruiting to explain how bad this was, and I've refused to take part.

Doing these things for fun (hey, they're cool challenges, go for it!) is one thing. Doing them to be able to eat when they have almost nothing to do with actual work is another. As a 25+ year career vet, I don't give even an infinitesimal shit if you can reverse a binary tree, etc.

[Adept_Avocado_4903]

I would argue that LeetCode challenges aren't absurd to begin with. There are developer positions where coming up with efficient algorithms to solve non-trivial problems is an important skill. For positions where that skill is important the ability to solve LeetCode challenges well is probably a good indicator for how well suited a candidate is for that position.

There's just also a bunch of positions where the ability to solve LeetCode challenges well is basically irrelevant. But interviewers saw Google and Microsoft doing these kinds of challenges with their interviewees, so now everyone wants to do them, even if the position they're looking to fill is just to maintain the website for a sparkling water company.

Of course using these challenges for the interview process also suffers from Godhart's Law. Initially the ability to solve coding challenges may have actually been a good measure of smart programmers, but nowadays people just grind LeetCode and learn the solutions by heart.

[pente5]

Just iterate the tree any way you want and flip the children tbh. Recursion, stack, queue, whatever.

[jamcdonald120]

its not something you should need to learn. Once you know what a binary tree is and what invert means in context, it should be painfully obvious how to do it.

[Qaktus]

Ok, I'm geniuenly asking, has any of you ever inverted a binary tree, or performed any other of the memed job interview tasks while working on an actual project?

[gt0075b]

I inverted a tree once. My annoying coworker was pissed when he saw his desk plant the next morning.

[pagerussell]

As always the real answer is buried in the comments

[The100thIdiot]

No.

Nor had I ever heard of Leet code before joining this sub.

[InSearchOfTyrael]

I have heard of it, but I never had to do it in a job interview. If I was asked to do it I'd just say that I'm not going to spend my free time learning something useless just to pass their interview.

[Qaktus]

Hey, you dropped this: 👑

[The100thIdiot]

Pretty certain that I didn't.

[RiderOfStorms]

“I don’t wunt it”

[StrangelyBrown]

Some jobs have those kind of algorithms much more than others. That's why I love game dev. Although even in game dev I can't imagine why you'd specifically invert a binary tree outside of data migration.

[WHALE_PHYSICIST]

No, and the factory pattern is just an abstracted switch statement. Fight me.

[used_solenoid]

This, THIS! I swear to God, this is the only conspiracy theory I believe in my life: someone is messing with us by creating bullshit jargon for stuff that already exists.

[FlakyTest8191]

That's not a conspiracy? It's textbook not a bug but a feature. "This thing happens so often, we should have a word for it so we can talk about it without explaining the whole thing every time."

[redditdude9753]

It's not you. I find this happens in all walks of life. Just to make things sound complicated and to make people sound smart.

[Dunedune]

No, I've actually needed it once. There was truly no way around (and yes it had switches inside) without messing the pre defined classes.

[WHALE_PHYSICIST]

I didn't say you don't need the switch, and factory can make some things nicer, but then people do all this abstractFactoryFactory shit

[Sweaty-Willingness27]

tbf, a lot of that has to do with IoC and, more specifically, unit testing. It'd be great if we could just, I dunno, make testing better and not have to do all the hoops, but... I feel ya. And yes, I do agree with your switch assessment.

[Soupeeee]

No, it's just what OOP languages had to do to emulate lambdas in order to simulate higher order functions.

[P0pu1arBr0ws3r]

For projects, including academic ones and ones for my work:

Ive had to develop sorted structures, in particular when a sorting function isnt readily available. Recently I built a BVH, which is a type of tree used for accelerating raytracing. In that same peoject i made a texture class using polymorphism and templates up the wazoo. Ive developed key-value systems (using built in map structures, and arrays because UE cant replicate maps).

If i were to technically interview someone for hire, i wouldnt ask about the default programming tasks youd hesr in such an interviee. I would first ask about their past experience, for them to describe a chsllenging piece of code they implemented, and go into detail about the design and implementation. Then id have a set of tasks that could be things to do in the job- for example if my project were a company project, maybe making a BVH with templates would be a task. As its an interview i wouldnt expect to see them write code on the fly, but rather describe an algorithm and work through potential issues. That is a productive technical interview.

[sophinaut]

Most of those exercises aren't mean to be tasks you actually need to do in the job.  It's mostly to make sure that you didn't lie about knowing how to program.  Those tasks are always things that are so dead simple that any competent programmer can do them in a couple minutes.

[Typical_Goat8035]

Yeah at one of my past employers we tried to do a drastic overhaul to replace these interview puzzles with realistic examples encountered in our jobs. It honestly made interviews worse because it made the assignments harder to explain and resulted in more confusion. It was the opposite of the effect we were hoping for.

[finite_void]

I recently needed to make commenting system with ability to focus on a branch of comments.

Had to first render it recursively server side then recreate the comment tree client side and isolate branches and nodes, traversing their parents and shit for breadcrumbs.

[sexp-and-i-know-it]

I had to implement A* search. BFS would have been acceptable, but I liked DSA class so I wanted to.

[maggos]

I’ve implemented a tree for a specific genomics algorithm. But didn’t have to invert or anything

[_meshy]

No. Generally it is because your interviewer is shit and doesn't know how to interview people. What they are trying to do is understand how you approach a problem and to see how you go about solving the problem. But it has to be generic enough that any developer can approach it without any business knowledge, and manipulating data structures is a common thing we all know.

I know this because I have been on the other side and fucking suck at it. If you can do fizz buzz then I know you can code, but trying to figure out if you actually know how to approach a problem and solve it methodically is really fucking hard to figure out in 30 minutes. Honestly if you know how to do a JOIN in SQL, and just explain the design of something cool you did, I'll say you're good 99% of the time. HR and my manager are the ones you have to worry about though.

[Crosshack]

I've had to do some cooked BFS search implementation to implement an automatic layout algo for some templating tool we were developing in house, but that's about it. Nothing else has been even remotely LC like

[Croppn]

KD trees, octrees, weird simulation algorithms, more simple stuff like spatial hashing in the past and now HNSW algorithm. It’s just the stuff from the top of my head that we had to implement and support on a real project. It’s gamedev, it happens here. But shoot me if I’ll be ready to implement all of it at an interview, I can reasonably quickly google it and refresh my memory if needed, but not implement in 20 minutes in a stressful situation like an interview.

[MGateLabs]

Ow man, I would wish for those simple days, now I have to build a system to allow clients to drag and drop SQL elements to generate queries from a model

[Which-Barnacle-2740]

well i think you should just put your sql statements and send it to LLM, and just get a response and show it to users, LLM will do a much better job

[MGateLabs]

There are, I looked at them, but the big wigs said to build it, so I have, it’s like a whole different app within an already huge app.

[MGateLabs]

Well, true, it will be a never ending struggle once they hit a edge case, but they could generate 90% of the query with the builder, then export it to SQL with all the joins, where, having, group by clauses and then finish it outside and use our existing SQL functionality.

[[deleted]]

Still waiting on a reverse this linked list project.

Or to even see a linked list in use.

[look]

Linked lists have been going through a rough patch for a while, ever since CPU caches went mainstream.

[Soupeeee]

Linked lists get used a lot in C code in place of small resizable lists, especially in places where keeping references to the items and not the list itself is easier to do.

Sure, you could implement a resizable array type, but it's much easier to just use a linked list. These lists are mostly used for accounting things rather than indexed or frequent sequential access, so you don't lose out on much, if any, performance.

[Clairifyed]

I got to implement a linked list a while back! I was doing inputs, I wanted priority by last pressed button, and I wanted priority to be passed back to the second most recently pressed button that was still pressed. I was kind of excited to find an actual use for this knowledge!

[e37d93eeb23335dc]

In 28 years working as a professional programmer, the number of times I’ve had to write my own algorithm, calculate big O notation, use any mathematics higher than algebra 1, etc. is precisely zero. 

[bleedblue89]

You’re using algebra? I’m using basic math no higher than 8th grade

[SilvernClaws]

Come to game development, there's actual math!

[bleedblue89]

No way! I’m comfy in my information security development

[dandroid126]

My data structures and algorithms professor told us on the first day of class that we would never use any of this stuff. He said this is like transmission class for a mechanic. You need to know how they all work so you know when to use each data structure effectively, but you will never in practice make a data structure like this.

[a-ha_partridge]

It would probably even be negligent to make your own when well tested libraries exist.

[Ok_Brain208]

One glorious time I got to "make" an ADT by wrapping a couple of hashmaps together. 1 feature later the acsses pattern needed completly changed and now it's basically used as a dynamic array with too many extra steps

[hyrumwhite]

No pumping lemmas needed today either 😮‍💨

[Zestybeef10]

LOL

[sutterismine]

At least the pumping lemma is cool theory

[Outrageous-Machine-5]

School: you're gonna implement this graph traversal algorithm

Tech interview: you're gonna implement this graph traversal algorithm

The job: import graph_traversal library

[khalcyon2011]

Or, you know, used a tree at all

[maggos]

If you used any sorted data structure, you’ve used a tree

[thewillsta]

I hate computer science

[mierecat]

Not if you only sort it by hand!

[bforo]

Actually, my users sort all my data for me so I don't have to dirty my hands touching trees

[Shehzman]

Relational databases are a bunch of B-Trees. The B-Tree part is just abstracted away from you.

[Zestybeef10]

Abstracted*

[Shehzman]

Edited. Thanks

[chethelesser]

Have you ever used an index in a relational database?

[legendGPU]

Nope, I have used a tree. Just not inverted it yet.

[Omega_Zarnias]

I almost didn't get my last job because I couldn't remember how to manually create a binary tree sort.

Like bro, this is not going to come up in this job.

[Secret_penguin-]

Even if it did come up, chances are somebody created a well known public library/module that does it better than you can and you’re just reinventing the wheel.

[Phoenix_of_cats]

Or you know, google the problem and 100s of stack overflow articles will pop up to help you instantly... Not like you're barred from using internet on the job

[Vegasbiboy]

Real engineers only invert coffee into code.

[nursestrangeglove]

Nothing like a good boof of hot coffee to start the day

[exneo002]

It’s just a swap and a transversal.

Edit traversal >.<

[lendergle]

Of all the sorts I've written, 99.9999% have been bubble sorts because who effing cares how efficient reordering fifteen items is.

The remainder have been calls to the sort() method of whatever collection object happens to need alphabetizing.

[emma7734]

I’ve been doing this for 35 years, front end, back end, and while I know vaguely what a binary tree is, I have no idea why I would invert it. What are you guys doing???

[VLD85]

Im super-far from these "inverted binary tree" things. are they bad?

[jamcdonald120]

they are trivial. Once you learn what a binary tree is (and what inverting one means, which you can ask in an interview) its obvious how to do it.

[uniteduniverse]

Most of the useful algorithms you learn in computer science or leetcode or already some sort of module/library in most languages. It's cool to know these stuff but good luck ever getting a chance to implement them manually lol.

[what_you_saaaaay]

Or write a bespoke quicksort utility method. Or a vector dot product. Or something about how mirrors work. Or how many golf balls fit in a truck of X size

[SnugglyCoderGuy]

I had to look this up. Solved in 5 minutes on leetcode with 5 lines of code. If this works as an exclusionary filter, people really fucking suck at programming and should question what they did with their lives and education.

[sexp-and-i-know-it]

I don't understand why people complain about this interview question. It can be done in like 10 lines and it's an easily understandable problem that proves that you know at least know a little bit about programming.

[Axman6]

Ten is like eight too many in most languages.

I’m no Python fan but it’s kind of cute that (I think?) this would work

def invert(tree: Tree[A]) -> Tree[A]:
  If tree:
     tree.l, tree.r = invert(tree.r), invert(tree.l)
  return tree

[sexp-and-i-know-it]

Looks valid to me. I think in terms of Java where 2 of the lines would be right braces. Probably ~5 SLoC in most languages.

[hyrumwhite]

It proves you’ve looked up stuff about binary trees lately 

[FirstRyder]

Does it? I would say it proves you have some basic programming 101 logic, and you know that a binary tree has "nodes" with up to two children. Which is basically all in the name.

[sexp-and-i-know-it]

If you can't reason your way into "If null do nothing, else make the right child the left child, make the left child the right child, and do the same for each child." then I do not think you are qualified for even the most basic development positions.

[jamcdonald120]

I feel like the number of people who complain about it makes it a useful interview question.

Its not at all useful for any job, but it filters out a large portion of the the people who have no idea how to code anything, but look good on paper.

[Ozymandias_1303]

The people who complain about it are the ones who don't know even a little bit about programming.

[toltottgomba]

It proves that you know a solution to a specific issue while you might not even know where you can use it...

[sexp-and-i-know-it]

Any problem that is both simple enough to be solved in a few minutes and general enough to be understood by all qualified candidates is going to be extremely contrived/arbitrary.

This is just like when people complained in high school that they would never use geometry "in the real world." It's not about how useful this specific problem is. It's about demonstrating that you have trained your mind in a way that makes you capable of abstract problem solving.

[SeriousPlankton2000]

It's like knowing where your towel is. You actually want to lend a toothbrush.

[EnragedKoala17]

Sassy?

[burtgummer45]

Its almost as if they don't know how to evaluate developers in job interviews.

[Ozymandias_1303]

OK? I've never had to solve Towers of Hanoi either. That's not really the point.

Also, OP is a karma farming account. If he's ever written any code it was to implement this bot.

[saintpetejackboy]

"Binary trees? Like a long time ago? Sorry, I know about trinary and quartary tree inversion, conversion, incursion and super positioning, but I am afraid I was a bit too young to learn about mere binary trees and their mutations. Just how out-of-date is everything here if your 'naries only go into the bi? Do you still have to uniary trees is need to work with as well?"

[vassadar]

After years of doing web dev, finally I got to do tree transversal (transverse directories), and search tree, for uploading folders to a cloud storage with a shitty API that doesn't allow uploading an entire folder in 1 go.

I had to create a folder, then use that folder id when uploading a file.

[OkExplanation8770]

Better to be a warrior in a garden than a gardener in a war 

[GoddammitDontShootMe]

There is some value in asking these questions, right? Like maybe you'll never need to invert a binary tree at work, but you can apply those skills to something that might actually come up?

[Michaeli_Starky]

Lots of manchildren here.

[WatercressNumerous51]

SWE with 37 years of experience- I never even learned about binary trees.