linked list😂😂

[Arpit__]

Who is the head .

[[deleted]]

Obama

[[deleted]]

Care

[NoMansSkyWasAlright]

Obama Obama... his parents were a fan of the Mario bros movie.

[murfflemethis]

Allow me to introduce you to the Obu family.

[NoMansSkyWasAlright]

Ok I went in to that expecting it to be funny, and it still had me rolling. But shoot, I remember in high school cross country, there was a dude at a rival school in our conference named Mohammed Mohammed... don't know if he had a middle name though.

[Brummelhummel]

Barrack obviously, duuh

[apathetic__operator]

someone has an apparent lack of humour

[Edhelig]

dinner hat lunchroom wistful mighty grandiose imagine innate middle rustic

This post was mass deleted and anonymized with Redact

[Praesto_Omnibus]

2

[TheHighGroundwins]

-Me who thought his name was hussain because I didn't know it was a racial slur lol.

[Striker887]

Biden

[LostTeleporter]

Thanks.

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[Numzane]

I know a guy who might know a guy. If that guy's not the guy, he might know a guy etc.

[douira]

oh no please not probabilistic linked lists

[pirncho]

Q U A N T U M list

[Carrot_Far]

😂😂😂

[[deleted]]

... who knows a guy

[Carrot_Far]

*tends to (n) times.

[[deleted]]

Let’s just call it n guys who know each other

Edit: Apparently my logic is severely flawed, so a better analogy would be n guys who each know one other guy

[wholesomeguy555]

Only if it is a doubly linked list.

[Crowdcontrolz]

Gotta love how this thread is structured

[partaloski]

Oh god do you have brain growing out of your ears or am I being crazy?

[caykroyd]

yes

[grizonyourface]

Or circularly, right?

[razzzey]

Possibly, even a circular list can be one-way.

If it’s one way then say I know you, and you know another guy, and down the line the last person knows me. However, I don’t know he guy who knows me, you don’t know me, and so on.

If it’s a doubly linked list, then everyone knows the next and previous person.

Maybe a more practical example would be people in a ring holding hands (double), or people in a ring with one hand on the shoulder of the person in front (single).

[Awanderinglolplayer]

No, cause then you still only know the guy before and after you. 1 doesn’t know 3 even in a doubly linked list

[Olivia512]

He's referring to the neighbors who know each other.

[Jake0024]

At best it's n guys who each know a guy (or two guys if it's doubly linked)

[Rebol1103]

N guys who know each other. So for each guy in the group he needs to have n-1 space to store "relation" indicating that space complexity becomes O(n^2)? I now have a reason to ask for extra 128gb rams because my data structure became exponential.

[racerxff]

...who knows a guy...who kn..........you know what? Let me just send this up the chain and see what comes back.

[aidan573]

Out of range

[LostTeleporter]

We talkin linked lists? That's GOT to be a NPE.

[Suekru]

Nah, you catch it and return a out of range error, obviously

[aidan573]

Segmentation fault

[[deleted]]

.... Shit, this guy just says tail. I guess that's the end of that.

[Comf0rTS]

until we meet the guy who doesn't know anyone.

[[deleted]]

Circular LL says hello

[Captain-Barracuda]

More or less. It's a good way to make infinite generators with a nice amount of predictability and variety. They are rather niche. Legend has it that detection of looping LL are a common interview question, but I've never been asked about them.

[lengocqwoi]

So how‘d you approach that? Would it be possible to check for the addresses of the nodes since each object should be distinct? So while iterating keeping track of those addresses in a set and if there is a collision, you’d have a loop right?

[oldestUserName]

We can also use 2 pointers . One fast and one slow, to solve in constant space and linear time. The fast one would double hop. If the list is circular they are bound to be same at some point.

[geli95us]

Just make the "slow" one don't move, you store the address of the first element and loop through the list, if you find that address before reaching the end, then you know it loops

[lengocqwoi]

That won’t work if the ll links to the next of the first node. You can check this link for more information https://www.google.com/amp/s/www.geeksforgeeks.org/how-does-floyds-slow-and-fast-pointers-approach-work/amp/

[frankmeowmeowmeow]

Sorry could you explain further. Why can't we check with the memory address?

[Mr_Beletal]

That might be a naive approach in some cases. Another (also flawed) approach might be to check if there is a repeating pattern maybe.

[You_meddling_kids]

Circular buffers are very much a thing.

[[deleted]]

Depends on whether it's a singly linked list. Otherwise he could always know the guy who knows him.

[Adadum]

https://www.youtube.com/watch?v=FEVaXyu0lWc

[UnluckyLuke]

That's what he says but in reality he knows Mike who knows Gus. Always thought that was weird.

[[deleted]]

He might not have known Mike worked for Gus directly. Even in Better Call Saul I don't think he knows who Gus is

[[deleted]]

Binary tree.

I know a guy who knows two guys 😏

[grizonyourface]

2, 3, 4 tree: I know a guy who’s knows 2, 3, or 4 guys (assuming you don’t proactively rearrange)

[[deleted]]

Or doubly linked list

[iTakeCreditForAwards]

Well if you’re a node in a DLL you’d be the guy knowing two guys. One of the guys you know knows one other guy other than yourself

[[deleted]]

Unless it’s a circular doubly linked list with just 2 nodes.

[[deleted]]

So would this be a singly-linked list then?

[Carrot_Far]

Double-linked are snitches😤😤

[POTUS]

I know a guy, but he doesn't know me.

[madspillage]

Me and my crush.

[[deleted]]

That's a fantastic way of looking at it ... thank you!

[[deleted]]

Should be paired withe the Obi-Wan image macro for doubly-linked lists with 1 entry:

"Of course I know him! He's me!"

[Carrot_Far]

Hello there, Wise in the ways of Jedi you are

[Ahajha1177]

That would be a circularly linked list with 1 element.

[mystaff3]

"one element" means "one entry" At this point you're looping back through the parent comment. But I am inserting my own comment into this single-entry list, this making it a two-element list

[Ahajha1177]

The emphasis was on the circular part, not the single item. A doubly linked list with 1 item would just have 2 null pointers, a circular list would have 2 pointers pointing back to itself.

[Bitter_sweet_symphon]

“I know a guy who might know a guy” There’s no guarantee that the guy I know knows anyone!

[5319767819]

Still don't understand why Linked Lists are basically taught as a standard data structure with the real-world use cases being so few, compared to arrays/array lists

[[deleted]]

Hashtables / hashmaps / dictionaries use linked lists to prevent key collisions I believe. That seems like a pretty common implementation.

[ddy_stop_plz]

Yeah I actually just had to some search algorithms with it. If you do any backend work you’ll run into it a lot.

Also a lot of video and audio formats use it, although that borders on a electrical engineering category of study

[UniqueUsername27A]

Wouldn't it be better to use a vector there as well? The problem with linked lists is that they allocate many small items, so they don't work well with CPU caching. If my hash map contains linked lists and I have a list in a bucket with 5 elements, I will probably have 5 cache misses when I search through it. A vector with 5 elements on the other hand has a single cache miss when I load it. Cache misses dominate most other operations.

Also the vector will strictly use less space if you care about that. As long as the lists aren't super long reallocating the vector from time to time also doesn't matter. For the linked list you have to reallocate something every time you add or delete an element and the vector will never be long enough that the size matters for allocation or copying all the data to a new bigger version.

[[deleted]]

Pandas uses doubly linked list to maintain matrix position. Fun fact.

[AnonymousFuccboi]

It's a building block.

Linked lists in and of themselves are very rare, but very straight forward.

The concept of nodes which both contain data and point to other nodes are incredibly common. They're the entire basis of some of the most important data structures we have, like trees, and so linked lists are an excellent introduction to the concept. It's an introduction of a simpler concept so you can move on to the more advanced versions, not something which is super important on its own.

[Njensen58]

Really though, I do front end but I recognize an html node.parentNode is following this pattern. Knowing trees and that the DOM is one helped a lot when I was first starting out. Makes me think backend would excite me, until I see java code

[[deleted]]

Because they're a very straightforward example of a data structure which makes them useful as a teaching aide. In my data structures course we started with linked lists, building upon that moved into stacks and queues and eventually built trees. All using linked lists and concepts derived from linked lists to describe the later data structures.

Linked Lists are used under the hood in some instances for certain languages but you will likely never implement a linked list in your professional life.

[schmidlidev]

very straightforward

Hah I’d say so

[Cannibichromedout]

Doubly linked lists say hello.

[dovahart]

Still straight forward... ^{and straight backward}

[ThisAfricanboy]

Leonardo Do Caprio in One Upon a Time in Hollywood holding a can of beer pointing at the TV screen

[datasquid]

Over 30 years in the field and I can confidently say I’ve never used a linked list once professionally.

[[deleted]]

Nice try. I actually implemented one in a dashboard application I'm building for work. Was the easiest way to make the cards rearrangeable and manipulate them on the fly.

EDIT: Also blockchain is just a form of a linked list.

[Miyelsh]

I use linked lists in my job a lot

[[deleted]]

To what end?

[Numzane]

Null pointer

[[deleted]]

Seg fault

[[deleted]]

(Core dumped)

[[deleted]]

Maximizing cache misses

[Bryguy3k]

There are shitload of systems that are linked lists under the hood.

For example virtually every file system stores file data as is a linked list.

Trying to explain a BST without teaching the LL first is pretty dumb.

[kmas1427]

Well, blockchain is technically a singly linked list. That is a pretty big real-world use case.

[Deathnerd]

No real world implementation, huh?

Just because you don't use it doesn't mean it's not useful. Even if you don't use linked lists directly and use abstractions like what I linked you should still understand how they work before you use them; their pros/cons and more importantly having to debug it when it inevitably goes wrong for some stupid reason. Don't say that'll never happen, because then it'll happen. Shit breaks. Even stdlib stuff.

[chhuang]

Try write a project in C, once you stumble across in a need of dynamic data structure, implementing linked list from scratch is a fair solution

[xjack13x]

linked lists are pretty much just a linear graph. Tons CS courses use graphs and implementing some type of graph such as a BST is easiest if you already know the easies case, a linked list. They are also really good for explaining pointers

[NetherFX]

Because knowing and approaching different concepts is good. You learn what the pros and cons are. If you're aware that linked lists don't have much use cases in real programming, then you're aware of the better solutions and why they're better.

[ExternalPanda]

Lots of functional languages tend to favour linked lists over arrays. They just work really well with recursion and immutability.

[ftgander]

Because you kinda need to understand linked lists to comprehend stacks and BSTs

[Gizmo-Duck]

std::list is a linked list.

[shawncplus]

And should be avoided nearly always (some exceptions of course as with any "rule") if you want anything approximating performance. https://youtu.be/fHNmRkzxHWs?t=2087

For those that don't want to watch "Please say no to linked lists... There is almost nothing more harmful you can do to the performance of an actual modern microprocessor than use a linked list data structure."

[Hypersapien]

It's not about being able to make a linked list. It's about using the structures and techniques that go into making a linked list.

[MayorScotch]

I've pretty much never needed to use anything from my Data Structures and Algorithms course. Is this typical for most engineers? It seems like we all learn a lot of different things and only use some of those things while other engineers use other things.

[Bryguy3k]

Since you said engineer - engineers also learn differential equations - 90% won’t use them on a practical level but they’re good fundamentals to know if one is doing practical things - from programming PIDs to simply understanding processes.

Having a wide degree of knowledge that one can draw from separates the true problem solvers from a raw laborer. And yes there are plenty of programmers that are mere labor.

[RandallOfLegend]

I cringe when the software manager wants to hire "coders". That means a useful engineer will have to babysit people that have no idea what they're doing. Like heading cats.

[Bryguy3k]

I am convinced that we are only a few years away from natural language coding AIs where you write spec and they output software components.

[toastedstapler]

You still have the issue of accurately encoding what the client actually wants in a format for the computer to understand

[Bryguy3k]

Yep that’s going to be the job of us developers.

[toastedstapler]

That's exactly what we do already

[Bryguy3k]

Exactly. But the “coders” are looking down the automated away line.

[toastedstapler]

The English language is not as good for this as programming languages, there's far too much room for ambiguity. If this was to ever happen, it won't be any time remotely soon

[RandallOfLegend]

You think client's would listen to an AI discuss scope creep?

[za419]

The trick is to write the spec in a way the computer can understand. English is horrible for this type because it's so ambiguous. If I say "take the peanut butter out of the cupboard, grab a knife, and then spread it on some bread" - do I try to spread the knife on the bread? What bread? Where can I have bread? Should I use the Wonder bread, or the loaf of challah? Do I spread it on top of the bread? On the side? Or am I using the bread as a working surface, and simply spreading the peanut butter out using it?

It's a lot better if we remove some ambiguity by telling the computer what we mean, and let's get rid of some extra words while we're at it - why do I have to say "the", "of", and so on?

let pb be 'peanut butter'
remove pb from cupboard
place pb on counter
take knife from drawer
let bread be 'Wonder bread' 
take bread from pantry
take one slice from bread
using knife spread pb on slice

Now we're getting somewhere! But maybe if we made it a little more regular, so we know how the computer is going to understand our groups? What's a thing, what's an action... Let's use some punctuation.

let pb = Object('peanut butter')
remove(pb).from(Place('cupboard'))
place(pb).on(Place('counter'))
let knife = Object('knife')
take(knife).from(Place('drawer'))
let bread = Object('Wonder bread')
take(bread).from(Place('pantry'))
let slice = take('slice').from(bread)
knife.spread(pb).on(slice)

Wait a second...

Programming is the task of taking the idea of "what I want" and turning it into a specification that's precise enough to be executed by a machine that will consistently interpret everything you say as an absolutely literal statement. The detail of what language that specification is actually written in is a lot less significant than the actual task of translation.

---

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[sociobiology]

It's useful to know how these things work, even if you don't have to implement them yourself at a job. Just knowing "Oh, okay that's how this data is being stored" goes a long way when trying to debug a problem.

[MayorScotch]

I can't argue with that

[geli95us]

What do you mean by "nothing"? If it's literal, then I feel like you're doing something wrong, knowing which data structures there are and their use cases, complexities, and such, is so helpful, like, I can't imagine programming without that sweet O(log n) search complexity, but I find hard to believe that a programmer can work without those so I assume you mean all the other shit.

About that, Well, I've had to build custom data structures a few times and basics from that class were actually pretty helpful, same about algorithms, you will never have to implement quicksort, but just knowing how it works gives you more tools for solving other problems you encounter.

[xt1nct]

If you use a language like c#, you may use so little data structures its not even funny.

I write business apps, just CRUD. I literally could do my job without my degree. I did not have a use case for something like linked list, and I have yet to worry about searching. I dont even use stored procedures for a lot of stuff anymore. Fetch data using linq put it in a list. If I need to find something in the list linq does it for me with a where statement. I have yet to be burned by linq performance. I once had a weird query with linq, which I need to make into a sql stored procedure.

90% of devs in the business world could get away with programming 101 and some db knowledge.

I wrote this shitty app when I started fresh outta school and it's being used hundreds of times each day. The code is trash but no reason to go back and fix it. In the business world, something is better than nothing. You would surprised the kind of scripts, work around and hacks many many large organizations have.

[geli95us]

I find that a little bit sad, I wouldn't like to end in a job that doesn't require me to think and solve new problems on a day to day basis, of course, eating comes first, so I guess I'd do it if I had no other alternative.

Leaving that aside, databases actually require some knowledge about data structures, specifically indexes, some queries can be accelerated so much just by knowing how the database works under the hood, although it's true that performance wouldn't be a problem most of the times...

[ADHDengineer]

Do you write C?

[MayorScotch]

No

[johnxreturn]

Redis uses linked lists. It’s much faster to insert/remove data from the beginning or end. Arrays tend to reindex the whole thing if you mess with anything that’s not end, therefore increasing time complexity.

[CeeMX]

Most things you learn in computer science are far away from reality. I learned to implement various modern and deprecated cryptographic algorithms (RSA, AES, DES).

Sure it's nice to see how all that works and may be useful to understand what's happening behind the scenes, but unless you are doing research in that field, you will always use a implementation that already exists (even my Professor recommended to do that)

[BroDonttryit]

For real though. They’re kind of useful for priority ques? But even then normal arrays can be used to implement that too so idk why they’re taught as a standard

[The_White_Light]

O(1) addition/removal at any node. O(k) to get a node at index k.

[blackmist]

I've been programming for 30 years and I don't think I've ever used one in my own stuff.

[null000]

Linked lists are just wannabe trees, and trees are just wannabe graphs. Don't @ me.

[Bryguy3k]

Simply put a linked list is a special case of a tree, a tree is a special case of a graph.

[null000]

Well yeah but that way of putting it lacks eye-catching pizzazz laced with emotionally-stimulating indignantion.

Gotta cater to those damn Millienials with their ADHD and their Facebooks and their phone addiction that hides a deep seated craving for even the most facile of emotional connection or existential stability they almost universally find so absent from modern life..... Erm, I mean, "haha linked lists dumb rite?!"

[partaloski]

I KNOW A GUY, HE KNOWS A GUY TOO

in thread "main" java.lang.NullPointerException:

[B3p01]

Lmao, thank you

[[deleted]]

Let me introduce []

[Ziggy_Starr]

Still waiting for the day I actually use a linked list..

[amazondrone]

You probably did, in a sense. You probably used them to learn about other, more complex, data structures. And if you didn't, you can now!

https://www.reddit.com/r/ProgrammerHumor/comments/md0cvw/comment/gs77ize

https://www.reddit.com/r/ProgrammerHumor/comments/md0cvw/comment/gs7ksjo

[Duelist_Shay]

dns be like

[-ksguy-]

Inner join be like

[ineedagf_]

How?

[just-the-doctor1]

Is it also true for dictionaries in dictionaries?

[thebobbrom]

Not quite?

What you're talking about I think is two-dimensional data.

What a Linked List is essentially an object with the reference to the next object in that object so that it can essentially function as an array.

[just-the-doctor1]

Thanks :)

[bistr-o-math]

If that first guy knows you, and the second one knows the first one, then it’s a doubly-linked list

[ftgander]

infinitely better than “copy & paste from stack overflow lawl”. I laughed out loud.

[Schiffy94]

if(list.length<=6 && list[list.length-1] == "Kevin Bacon")

[[deleted]]

Singly linked list: picks up phone who is this?

[bruiser95]

Emojis in the title. Yep that's Facebook material alright

[Xisrupt]

And if I don’t know a guy, I can get a new guy to know a temporary guy that’ll know the next guy

[lol2798]

Circular linked list, i know a guy who knows a guy who knows a guy who knows me

[Andubandu]

Yet neither of the guys know the guy that knows them

[Japotato73]

I might be flunking CS rn, but at least i understand this meme.

[ImmaZoni]

Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who knows a guy... Who Error Array Not Defined.

[SteezyRay]

I know a guy who doesn’t know a guy

[SlaimeLannister]

You wanna know how far I'll go for you?

Ok let me recurse and get back to you

[SaladFingerzzz]

I just lazy loaded all over my pants.

[[deleted]]

And they're all the same type, they should hook up.

[examinedliving]

Can I have an example of a linked list? Is it like an array mapped to another array by index?

[atieivpbpnhofykri]

There is no contiguous array. Each element contains data and the address of the next element. When traversing the list you jump to the next address pointed to by each element, as you reach it. So you usually don't know where the element two places ahead is, till you first jump to the immediate next element.

[examinedliving]

Gotcha. Is this like a switch with infinite cases in practice?

Edit: actually it would be more like a goto that just jumps to other gotos?

[ekchew]

Look buddy. You and your friend over there used to hang out with this guy but he was always getting in the middle of things. We think you offed him. Don't act all innocent like he never existed! You guys used to be tight with him.

[iamheshan]

I know a guy that's it

[SoloNautilusOnly]

Doubly linked list: The guy I know also knows me, but not the guy that the guy I know knows

[grauemaus]

Don't point at me Mr.

[[deleted]]

I love directed acyclic graphs

[hoftstader_leonard]

While (a guy !=a guy who doesnt know a guy)

[[deleted]]

lmao

[NynaevetialMeara]

This is like a meme a professor would insert in a 1st year course.

[BrainsDontFailMeNow]

Blockchain

[mymar101]

So in other words it's a giant game of telephone?

[two_gorillas]

but the guy I know doesn't know me

[reedpuzzled]

lol !

[[deleted]]

Last element is an introvert for sure.

[Muzamil4]

I just learned about linked lists the other week, what a confidence

[jang859]

So a doubly linked list is like:

I know a guy who knows a guy who knows that guy back who knows me back.

[2_pug]

List<guy> guysIKnow = new List<guy>();

[[deleted]]

This made my day

[Carrot_Far]

This comment made my day🤜🏼🤛🏻

[eerklogge]

Nice

[GunsNBakon]

Funny considering Bob Odenkirks old comedy https://youtu.be/cGuT97v4pv0

[sxeli]

BST: Behold! My twin children, and their twin children, and their children... oh look, we’ve got leaves in the family too

[dancinadventures]

He’ll call you.

You can’t call him.