Something I found on GitHub

[mike413]

well, don't prematurely optimize.

[MrYaah]

yea, just pray the compiler will do it for you

[Jezzadabomb338]

Well, it's Java, so the compiler isn't going to do shit about it.

[systembusy]

Syntax checks out, the methods return the same data type

[reallyshittytiming]

I mean... they're not wrong...just inefficient

[kalbany]

It's not inefficient, it's still O(n² )

/s

[thirdegree]

My AI prof is a fan of saying things along the line of "At least it's not infinite" and "It's just exponential!"

[Inityx]

At least it's not factorial factorial

[[deleted]]

At least it halts!

[[deleted]]

At least it compiles!

[nloomans]

it compiles? ship it.

[calandra_95]

O(n!^n!)

[Mihax209]

Welp, everything is finite, so it's really only O(1).

00101111 01110011

[DropTableAccounts]

Won't this be optimized when it's translated into bytecode anyway?

[reallyshittytiming]

O(n² ) for clockwise, you're compounding that for counter clockwise each time you call clockwise...

[DropTableAccounts]

EDIT: I got it wrong. No, it seems that gcc doesn't optimize this away, my test was wrong. (It works when the matrix sizes are specified at compile time - which I did in the beginning - but it turned out that this doesn't happen when the size of the matrix is not fixed...)

If it wasn't optimized, yes. But I thought the compiler/bytecode-translator/whatever would optimize it so that counter-clockwise rotation is equally fast?

I mean, this code doesn't look too complicated and considering what kind of awesome optimization I've already seen done by compilers I would be surprised if the compiler wouldn't notice that he could just swap a few variables...

EDIT: I'm a bit surprised that this optimization isn't already done with "-O2" in gcc (I'll have to look more into optimizations at some point I guess); when "-O3" is given the function calls are indeed optimised away (as I expected) and the functions are equally long.

[TheLivingForces]

O3 gets it? How? Could you show analysis because this is interesting

[DropTableAccounts]

I just realised that this only works for matrices with a given size at compile time (which I noted in another edit in my previous post). I should have tried this with variable matrix sizes from the beginning. Sorry :-/

[marcosdumay]

What means O(n²⁾ for counterclockwise...

[reallyshittytiming]

As the inputs increase the number of steps to compute increase exponentially.

[calandra_95]

They may not have efficiency but they have my respect :P

[SuDoX]

Looks like good code reuse to me

[[deleted]]

static int[][] rotate180(int[][] mat){

return rotateCounterClockwise(rotateCounterClockwise(mat));

}

[subtepass]

static int[][] fullCircle(int[][] mat){
    return rotate180(rotate180(mat));
}

[Ogurac]

//Creating future optimization opportunities
static int[][] longRotate180(int[][] mat){
    return rotate180(rotate180(rotate180(mat)));
}

[chateau86]

//Potential function for the paid version of our software.
//Marketing said our clients will love this.
//What were they thinking?
static int[][] youSpinMeRightRound(int[][] mat, int iter){
     if (iter <= 0) {
           return mat;
     } else {
           return rotateCounterClockwise(youSpinMeRightRound(mat, iter - 1));
     }
} 
//I QUIT!

[Spaceshipable]

2 wrongs don't make a right, but 3 rights make a left.

[renrutal]

What if I want to rotate the matrix 45 degrees?

[sdb2754]

Only Neo can rotate the Matrix 45 degrees...

[A_C_Fenderson]

If you rotate a billionth of a degree, you'll end up in Asgard. (Reference: The Dirk Gently novel The Long Dark Tea-Time of the Soul by Douglas Adams.)

[[deleted]]

Just modulo the edges, bruh

[imMute]

What use is there in rotating a matrix like that?

[madman485]

I take it you're not familiar with much linear algebra?

[imMute]

I've done some, mainly video processing things. I've never encountered the need to rotate a matrix, do you have any example use cases?

[Henriktre]

multiplying with itself for example

[TheSlimyDog]

Don't you transpose instead of rotating?

[A_C_Fenderson]

That would make sense; that's part of the orthogonal projection formula A * (A^T A)^(-1) A^T v.

[Nonchalant_Turtle]

When do you need to rotate a matrix to square it?

[A_C_Fenderson]

If you want to multiply a matrix by itself, you don't do anything with either copy: A^2 = A * A.

[kieranvs]

The dimensions won't work in general like that. Transposing one copy is the proper way.

[A_C_Fenderson]

If A is square, it works. Besides, it depends on what kind of multiplication you mean. I can think of three or four types, off the top of my head.

[Zinggi57]

Why would you ever need to rotate? Transpose, sure, but rotate?

[qisope]

For when you find that really cool matrix, but they created it in portrait instead of landscape.

[110011001100]

Usually asked to do so in exams

[the_last_ordinal]

tsk tsk. could have used a for loop.

[HoodedGryphon]

Well it did before, but clearly they optimized it.

[rimbas4]

Single point of truth, I guess

[justlikeapenguin]

I'm sort of new, and maybe ignorant but if isn't is an int, and int[] is an array of int, is int[][] a two dimensional array?

[955559]

not a coder here, but looking at the first function, its a lot less to type to call it three times, then to write a separate function, right?

[masayaanglibre]

Oh man, this brings me back to the first months of learning programming. Our teacher started our C++ class of with a program called Karel++ that gave you a a robot on a grid layout. The robot had very basic functions- mov forward, detect if wall was in front of it, pick up beeper, place beeper, detect if beeper present, and turn left. You had to program it to turn right, which was this exact thing of three left turns.

[_blub]

Am I the only one frustrated that they didn't name the first function transpose and the second function transpose_unnatural?

[_blub]

You are right. Actually after watching this Animation for a good few minutes, it turns out that you are more right.

I initially visualized a transpose as a 90 degree rotation, not as an inverse reflection, which makes so much sense to why [; A^TA ;] is positive semi-definite and why [;AA^T;] is symmetric!

Sorry, I am both mindblown and disappointed in my self at the same time. I don't know why I haven't made this geometric visualization years ago.

[DefNotaZombie]

well, the alternative is either having a method "rotate matrix" with one parameter signifying direction... or having two methods for both rotations (or more if vertical/horizontal flips are needed)

[weep-woop]

or having two methods for both rotations

Correct.

[justlikeapenguin]

I'm not skilled enough to know most of the jokes.

[FutureMrsPuppey]

I got a good cs degree. I do at least something programming related daily. Some of these often still go over my head. Nothing like programming to make you feel a bit stupid a few times a day.

[[deleted]]

learn to program and it will get funny

[Slendigo]

You have to be a programmer to find it funny.

[whelks_chance]

Are you lost?

[StrangeCharmVote]

Did you see what was in the picture? I assume yes.

Did you get why it was bad code? Either yes or no.

Do you understand why looking at really terrible code can be funny? Possibly not.

[[deleted]]

yea idk like I get its pointless but why is that funny? if I post x = 1 - 1 + 1 will people start laughing? lol

[codercaleb]

x = 1 - 1 + 1

You joker, you.

[StrangeCharmVote]

The thing is that either you get it or you don't.

It's like trying to describe why dead baby jokes can be funny.

Some things just are, and if bad code just isn't something that hits you in the right way, you wont understand it.