The Nineteenth Byte

DialFrost

10:21 AM

pxeger?

lyxal

10:32 AM

@emanresuA bruh moment

pxeger

@DialFrost yeah ok that's what I meant

that's probably not as interesting in my opinion, because it just combines a whole load of separate challenges into one

and in fact:

20

Q: Classify Quadrilaterals | Help me with my math exam!

Help! My math exam is coming up soon and I didn't study! 1 Part of the exam is to classify a quadrilateral given its vertex coordinates, which I, unfortunately, do not know how to do. 2 So, your challenge is to write a program to do this for me so I don't fail! Challenge Given four vertices su...

DialFrost

10:49 AM

ok nvrm lol then

Razetime

@null lol where

PyGamer0

hey look what i made: Try it online!

DialFrost

wut that

PyGamer0

i call it: chessboard creator 9000

DialFrost

lol

PyGamer0

10:59 AM

@DialFrost Try it online!

DialFrost

nubad

pxeger

@PyGamer0 61 bytes

New Posts

11:26 AM

0

Q: Products all the way down

You are probably familiar with the Cartesian product. It takes two lists and creates a list of all pairs that can be made from an element of the first and an element from the second: \$ \left[1,2\right] \times \left[3,4\right] = \left[(1,3),(1,4),(2,3),(2,4)\right] \$ Here the order of the resul...

code-golf math ragged-list

DialFrost

pxger the way u say "the obv" makes me look dumb hah

i have zero idea wat ur doing

:/

PyGamer0

12:32 PM

Wheat Wizard

1:40 PM

CMC: What is the smallest egyptian fraction representation of 3? I can do it in 13 fractions.

pxeger

1:53 PM

(approximately) how big is the maximum denominator in your solution?

Wheat Wizard

Less than 50.

pxeger

There are no solutions with denominators < 100 for lengths upto 8

Wheat Wizard

The largest 10 don't even sum to 3, so that's a given.

pxeger

my bruteforce C program seems to stop being efficient after about length > 10. I wonder if it runs out of registers

Wheat Wizard

How smart is "brute-force"?

pxeger

1:58 PM

not whatsoever

Wheat Wizard

Like it's not even assuming that some fraction larger than 3/n is present in an n term solution?

thejonymyster

i think if it is smart, it isnt brute force by definition, am i wrong?

Wheat Wizard

Brute-force is a continuum.

thejonymyster

ah right

pxeger

@WheatWizard nope

I couldn't even be bothered to write a combinations function in C, so I wrote a Python script which generates a C program for a given length

bit.ly/3qC8fG0

Bgil Midol

2:00 PM

How to tokenize text? (e. g *2 3)

pxeger

the fact I'm using long long ints probably doesn't help

Wheat Wizard

How are you calculating reciprocal sums?

(please don't say floating points.. please don't say floating point..)

pxeger

as if you multiplied both sides of the equation by the product of the denominators

so 1/a + 1/b + 1/c == 3 is calculated as b * c + a * c + a * b == 3 * a * b * c

Wheat Wizard

Ok, yeah if you did floating point the results would be basically worthless.

You might still have issues with long, long since the denominators grow on the order of factorial.

pxeger

@WheatWizard it would be faster though!

maybe this could be run better on a GPU

although they're not generally that good at large integer calculations

Wheat Wizard

2:03 PM

I would add some basic common sense optimizations before running on a gpu.

pxeger

common sense?

I'd rather die!

@WheatWizard does gcc -O3 count?

Wheat Wizard

No.

pxeger

lol

Wheat Wizard

This problem is actually brute forcable without "shortest with denominator under x" style restrictions. Which is kind of neat. It's the kind of problem that you could see not being brute-forcable.

pxeger

for the challenge I only needed a few high-ish test-cases, so it was faster to just let it run unoptimised than it would have been to implement any optimisations

Wheat Wizard

2:06 PM

Yeah, but for this it probably isn't. I ruled out all the numbers less than 10 in less than 10 seconds which is probably a good deal quicker than your program could.

?

pxeger

oh lengths less than 10

ignore me

Wheat Wizard

Ok Time to write a haskell "brute-forcer".

pxeger

I've got a 13 as well

not a very good method though

Wheat Wizard

Is the largest denom 42?

pxeger

no, smaller

Wheat Wizard

2:13 PM

Interesting.

Mine is: 1+2+3+4+5+6+7+8+9+15+18+40+42

pxeger

mine is 1, 2, 3, 6, 4, 5, 8, 9, 10, 15, 18, 20, 24

Wheat Wizard

Why is the 6 in placed weirdly?

pxeger

because it was formed from 1/1 + 1/2 + 1/3 + 1/6 + 1/4 + 1/5 + 1/8 + 1/9 + 1/10 + 1/15 + 1/18 + 1/20 + 1/24

each of those sublists sums to 1

and they're (some of) the shortest 3 disjoint solutions to my original challenge

Wheat Wizard

I just ran greedy up until I exceded 3 and then fiddled with it.

pxeger

~~I have a 12~~ wait no it has a duplicate in it

Wheat Wizard

2:26 PM

My program found no elevens.

It was so fast I actually thought I had a bug for a minute.

pxeger

What optimisations does it use?

Wheat Wizard

import Control.Applicative

check n s =
  compare (sum [div (product s) i| i <- s ]) (n * product s)

f n =
  go
  where
   go _ [] =
     Nothing
   go xs (y : ys) =
     case
       check n (xs ++ y : ys)
      of
        EQ ->
          Just (xs ++ y : ys)
        LT ->
          Nothing
        GT ->
          if
            elem (y+1) xs
          then
            go (y:xs) ys
          else
            go xs (y+1:ys) <|> go (y:xs) ys

It takes a starting guess greater than the goal best is [11,10,9..1] and it just makes things larger until the result is smaller than the goal.

It's not very smart or anything.

pxeger

that's actually pretty much what I was doing by hand just now

Wheat Wizard

It's really slow for 12. Especially considering how it took like 1 second to do 11.

ta Radvylf srik su shilani

1

A: Sandbox for Proposed Challenges

BCD to binary, with bitwise atomic-code-golf In this challenge, you'll convert an 8-digit BCD (Binary Coded Decimal) number to a 32 bit (unsigned) integer in the fewest instructions possible, with only bitwise instructions available. Task: You'll be given a single positive integer as input, from...

Not sure if I should go with the first or second set of instructions

The second adds goto and goif, and four more registers.

New Posts

2:39 PM

0

Q: Compress and decompress

Your task is to make a bidirectional compressor. It takes a list of bytes as input and returns a list of bytes as output. It has the property than whenever it is iterated twice it returns the original input. In other words, if f is your program as a function, then f(f(x))=x for all x. Now, since ...

code-golf compression open-ended-function self-referential

pxeger

@pxeger Is it possible to have a solution summing to 3 where no subset sums to 1?

I suspect so

ta Radvylf srik su shilani

@NewPosts Of course, this would be useless as a compression algo in real life because any input is equally likely to decompress to something lol

Wheat Wizard

I suspect so.

However it can't do better than 13 for sure.

Since 1/1 sums to 1 and not having it means the minimum score goes up by a lot.

PyGamer0

@WheatWizard is that haskell?

Wheat Wizard

Yes

If I want to rule out 12s I'm going to have to come up with some more optimizations.

pxeger

2:48 PM

an alternative method is just to look for sets of length 8 which sum to 1 and don't contain 1, 2, 3, or 6

Ginger Industries

hello

Wheat Wizard

For me I'm not really so much looking for a solution as I am trying to show there is none.

Bgil Midol

hello!

Wheat Wizard

I'm pretty sure 13 is optimal at this point. I just want to rule out 12.

Ginger Industries

stack exchange chat be like

pxeger

2:53 PM

I made a userscript to remove those messages lol

I don't have it any more though

ta Radvylf srik su shilani

That likely only happens if you've got someone ignored

I've never seen two distinct "x hours later" messages before

pxeger

there will only be consecutive messages if you have someone ignored, I think

Ginger Industries

@taRadvylfsriksushilani you're right, that is what happened

pxeger

but I find them irritating in general

Ginger Industries

also I released the first test version of an MC mod I've been working on

Wheat Wizard

2:55 PM

An optimization I'm thinking of is that if removing a value causes the sum to still be larger than the goal, don't bother incrementing it, just move onto the next one.

But there's a bug in my code and now it instantly claims there is no solution.

PyGamer0

@GingerIndustries thats so cursed

Ginger Industries

@PyGamer0 that... is the name of the mod mate

@PyGamer0 also I updated the release info to add the Water Sword

Wheat Wizard

Found a new 13: 14,20,28,40,10,8,7,6,5,4,3,2,1

PyGamer0

@WheatWizard are Egyptian fractions just fractions with numerator 1?

Wheat Wizard

Basically.

They are sums of distinct positive integer reciprocals.

Ginger Industries

3:02 PM

@WheatWizard what are these words

pxeger

integer you know

"integer reciprocal" is 1/x where x is an integer

distinct means you can't have the same one more than once (so 1/3 + 1/2 + 1/3 is not allowed)

and sum you know

Wheat Wizard

@WheatWizard Not a bug, this optimization just doesn't work with the existing algo.

Ginger Industries

@pxeger int("you know")

I'm accepting ideas for Cursed Additions btw

Bgil Midol

@GingerIndustries make a+b do a+1-b+a

Ginger Industries

@BgilMidol I'm sorry what

Bgil Midol

3:07 PM

2+2 becomes 2+1-2+1 = 0

Ginger Industries

@BgilMidol ...damn you that's an incredible pun

wait was that intended

Bgil Midol

@GingerIndustries whats the pun?

@GingerIndustries probably not

Ginger Industries

@BgilMidol Cursed Additions is a Minecraft mod

Bgil Midol

oh

@GingerIndustries allow the user to ride trees

ta Radvylf srik su shilani

High quality unintentional puns be like

Bgil Midol

3:09 PM

and climb trees

Ginger Industries

@BgilMidol ...vines

ta Radvylf srik su shilani

Add saddled leaves

Trees have a 1/100 chance of spawning with a saddled leaf block at the very center on top

Bgil Midol

@GingerIndustries add a enchanting-table-language to katlani translator hidden in end crystals

Ginger Industries

@taRadvylfsriksushilani this is a cool idea that would take me forever to implement

ta Radvylf srik su shilani

Can someone extract the code from this?

pxeger

3:11 PM

x=>x.replace(/pl|1/,z=>+z?'pl':1)

ta Radvylf srik su shilani

Thanks!

hyper-neutrino

i find it annoying that class methods can just sometimes lose awareness of who they belong to in js :/

ta Radvylf srik su shilani

Yep. Apparently it's for perforance reasons, but I hate it so much

PyGamer0

@WheatWizard so each fraction should be used once?

Wheat Wizard

At most once.

It can be used zero times of course.

ta Radvylf srik su shilani

3:19 PM

Can someone take the code from this too? (sorry)

pxeger

x=>x.replace(/11|0/,z=>!+z*11)

ta Radvylf srik su shilani

Thanks

pxeger

wow, that's short

PyGamer0

heres what my C++ program generates (wow i did it in C++):

1/2 + 1/3 + 1/4 + 1/5 + 1/6 + 1/7 + 1/8 + 1/9 + 1/10 + 1/11 + 1/12 + 1/13 + 1/14 + 1/15 + 1/16 + 1/17 + 1/18 + 1/19 + 1/20 + 1/21 + 1/22 + 1/23 + 1/24 + 1/25 + 1/26 + 1/27 + 1/28 + 1/29 + 1/30 + 1/31

Bgil Midol

@PyGamer0 what problem are you doing?

ta Radvylf srik su shilani

3:23 PM

This too

(Hopefully the last time?)

pxeger

x=>x.replace(/-?1/,z=>-z)

damn, that was literally the zsh answer I'm writing now!

ato.pxeger.com/…

(doesn't quite work yet)

ta Radvylf srik su shilani

3:45 PM

Can someone take the code from this please?

I really need to get Avi's TIO link API working

PyGamer0

@BgilMidol Wheat Wizad's cmc

i fixed my C++ program

ok this is very hard lol

1 -> 1/2 + 1/3 + 1/4

hyper-neutrino

x=>x.replace(/-2|1/,z=>~z)

PyGamer0

@WheatWizard how do i detect which fractions to not use, my results are weird lol

pxeger

@taRadvylfsriksushilani that one doesn't work btw

ta Radvylf srik su shilani

Seems like it should

pxeger

4:00 PM

when it runs on itself it gives the same length output, it doesn't compress it

ta Radvylf srik su shilani

Really? It shouldn't...

Yeah it's a byte shorter when compressed

There's no /g flag

pxeger

oh cause of the g

yeah I see

PyGamer0

@WheatWizard how many fractions do you get for 2 and 1?

@pxeger what about you ^?

Wheat Wizard

For 1 I get 1. For 2 I get 4.

pxeger

same

1 is obviously the minimum for 1

PyGamer0

4:08 PM

so 1/1 is allowed?

Yeah.

I'm 99% sure 2 is 4

oh

If it's not the sequence just offsets by 1.

PyGamer0

cool i get 1:1, 2:4, 3:11

let me fix my code a little and try again

ok same results

pxeger

4:11 PM

Anyone know what is the point in "you may only load the comment flag dialog every 3 seconds"??

@PyGamer0 3:11? What's the 11?

Wheat Wizard

There's no way to get 11 for 3.

PyGamer0

i think this is wrong: 3 -> 1/1 + 1/2 + 1/3 + 1/4 + 1/5 + 1/6 + 1/7 + 1/8 + 1/9 + 1/10 + 1/15

pxeger

yeah that's what I thought

Wheat Wizard

Are you trying to use floating points?

PyGamer0

yes

wait let me share my code

Wheat Wizard

4:13 PM

Floating points just will not work.

ta Radvylf srik su shilani

4:31 PM

My offline TIO link decoder site works now :D

hyper-neutrino

\o/

ta Radvylf srik su shilani

I should make it bidirectional

So that you can generate TIO links offline too

New Posts

0

Q: Remove odd indices and double the even indices

Your task is simple, just remove the odd indices and double the even indices Example the input is Hello, World! and we get indices H e l l o , _ W o r l d ! 1 2 3 4 5 6 7 8 9 10 11 12 13 and remove the even indices el,Wrd Double! eell,,WWrrdd and you are done 1-Indexing Test cases abcdef =>...

code-golf string array

Fmbalbuena

^ 3 votes in sandbox so this is fine

Wezl - y izl

4:48 PM

@taRadvylfsriksushilani sounds very helpful O:

ta Radvylf srik su shilani

I'll merge it into an HTML file and put it on GH

tio-offline-decoder.html

mathcat

what does it do?

ta Radvylf srik su shilani

It extracts all the info from a TIO link

So if you can't access TIO for some reason (which I can't, due to my school blocking it), it'll let you read people suggested golfs and stuff

Fmbalbuena

@hyper-neutrino Can you remove edit?

Wezl - y izl

> <script src="util.js"></script><script src="tio.js"></script>

mathcat

4:57 PM

oh nice

@taRadvylfsriksushilani why's your school blocking tio?

Wezl - y izl

mine is too btw

pxeger

nvm util.js must be being used

hyper-neutrino

@Fmbalbuena ?

Fmbalbuena

sorry

ta Radvylf srik su shilani

@Wezl-yizl Fixed

mathcat

5:00 PM

is there some IO rule for allowing 0 indexing?

ta Radvylf srik su shilani

You're allowed to use both 0 or 1 indexing by default

But if the question makes any rules, those take precedent

pxeger

@taRadvylfsriksushilani still doesn't work though

ta Radvylf srik su shilani

@mathcat My guess? The word fuck in brainfuck

pxeger

but SE chat contains the word fuck and it isn't blocked

hyper-neutrino

ah yes

mathcat

5:02 PM

@taRadvylfsriksushilani lol

hyper-neutrino

surely high school students won't know about these bad words if we block it

ta Radvylf srik su shilani

Oops, forgot to copy over a constant

Fixed

pxeger

cool

Wezl - y izl

my school system's restrictions system says "Non-Managed" which i think means that their bot just doesn't care enough to allow access

ta Radvylf srik su shilani

Oh hey, mine does too

It's not ContentKeeper by any chance, is it?

Wezl - y izl

5:05 PM

it is

ta Radvylf srik su shilani

So anything blocked for me is likely blocked for you, then. I think they use the same base list of things to block.

Wezl - y izl

hooray it's working (the TIO url decoder)

ta Radvylf srik su shilani

I'll get it to work for bidirectional stuff soon

so it can also be a TIO link encoder

Wezl - y izl

url is common enough to be lowercase but TIO is not quite :P

Fmbalbuena

tomorrow i will get Fanatic badge

@DLosc Is there a way to get indices in Pip?

Sandbox Posts

5:20 PM

0

A: Sandbox for Proposed Challenges

code-golfcipherstring Crack the Caesar cipher The Caesar cipher is a simple and famous cipher, where the letters of the alphabet are rotated by some secret amount. For example, if our secret rotation is 3, we would replace a with d, b with e, w with z, x with a and so on. Here is an example (rota...

thejonymyster

any feedback for this? I feel like the challenge itself is pretty interesting, personally, but i dunno

in particular i'm not sure how to approach defining the challenge in explicit terms. tricky

oh wait, i've got something

pxeger

sorry I misread it

Fmbalbuena

global flag in retina?

thejonymyster

ok so if some things were in the same proportions as eachother, like 10:5:20 and 2:1:4, thats the like, word id use

but how would i say it if theyre like...

pxeger

yeah I know what you mean

thejonymyster

5:29 PM

how would i say that "ranking by amount" is preserved?

pxeger

the relative ordering between every value is the same?

thejonymyster

100:99:2:1 and 50:40:30:20

right but its tricky because like

ta Radvylf srik su shilani

My hobby: Asking for feedback on other people's challenges

thejonymyster

@thejonymyster if i give you aaabbbbcc and aabbbbbbbbbbbbc they have to be in... the same.. thing

Fmbalbuena

CMQ: global flag in Retina?

thejonymyster

5:31 PM

@thejonymyster the relative order between every... amount of each value? is the same?

pxeger

@taRadvylfsriksushilani Any feedback? I'm not sure this challenge will be very popular ;)

6

thejonymyster

oops i accidentally made it reply to itself

pxeger

now you made a loop lol

thejonymyster

dios mio

ta Radvylf srik su shilani

@pxeger Lacking in focus and objectivity. Low effort proportional to difficulty to answer. Not a good fit for the site.

We should historical lock that, honestly (or at least close it)

Fmbalbuena

5:33 PM

@thejonymyster Necesitas un tilde en la letra I para ser gramaticalmente correcto

hyper-neutrino

jokes aside IMHO tetris GoL is actually a majorly overrated challenge in terms of the challenge post itself. it's certainly interesting but the majority (or rather, basically all) of my interest in it comes from the answers

mathcat

@taRadvylfsriksushilani that definitely needs an off topic flag

thejonymyster

@Fmbalbuena ah i never knew where the accents go lo siento

plus this keyboard doesnt give me easy accent access sadly

ok i just sent this link but i gotta get back to work so im gonna post it once more for the road: just edited this a bit, any feedback is appreciated, but no pressure

DLosc

@mathcat It's underspecified, probably, but why is it off topic? It's a language-specific golf challenge (that happens to be incredibly hard to solve, and then, incredibly, got solved anyway).

thejonymyster

see ya

mathcat

5:37 PM

@DLosc no, IMO it's a great question

Fmbalbuena

@thejonymyster ÓK, névérmínd bút whý ýóú dónt hávé ácénts?

2

DLosc

@mathcat Oh, okay. You were responding in kind to Redwolf's original sarcasm.

mathcat

yes

ta Radvylf srik su shilani

@DLosc It's incredibly subjective and underspecified. NDC, not off-topic, IMO.

(My comments on it were not sarcasm, btw. I am not a fan of tetris gol)

DLosc

@taRadvylfsriksushilani Remind me, NDC = ?

ta Radvylf srik su shilani

5:39 PM

Needs Details and Clarity

DLosc

Aha

ta Radvylf srik su shilani

I don't think that's actually a term people use, now that I think about it

Fmbalbuena

@taRadvylfsriksushilani No, Needs details or Clarity

ta Radvylf srik su shilani

Yep

DLosc

@taRadvylfsriksushilani I agree, but I do like the question (and even more so the answers it generated). I'd love to see more questions and answers on this site that prompt that "What the heck? How?!" response.

ta Radvylf srik su shilani

5:42 PM

Sure, but they should be properly specified

mathcat

But it could belong to meta too

Sandbox Posts

0

A: Sandbox for Proposed Challenges

code-golfpalindrome Recursive palindromes A palindrome is a word which is spelled the same backwards and forwards. For example, "racecar" is a palindrome as is "redder". A double palindrome is a palindrome whose halves are also palindromes. For example, "abbabba" is a double palindrome, as the half

Bgil Midol

6:16 PM

Shortest way to flatten zip object?

ta Radvylf srik su shilani

Okay, CMQ: You have two options. You can either have your screen auto-dim all the time and make things look weird, or you can have pretty bad scren tearing

Which do you choose?

Bgil Midol

@taRadvylfsriksushilani whats scren tearing?

ta Radvylf srik su shilani

It's where, when you scroll, it looks kind of jittery

Sandbox Posts

0

A: Sandbox for Proposed Challenges

Prime Number Fibonacci In this challenge, you will make a program that calculates the Fibonacci sequence with a twist. Instead of it starting with 0 and 1, it starts with the nth prime number determined by input by the user. The second number is the nth+1 prime number. The sequence should also st...

ta Radvylf srik su shilani

One part of the screen will scroll at a different time then the rest, so little lines show up as a result

Bgil Midol

6:20 PM

@taRadvylfsriksushilani auto-dim

ta Radvylf srik su shilani

Idk, it's pretty annoying

The screen tearing is mostly possible to ignore

Bgil Midol

gif of screen tearing happening?

Unrelated String

...i’m in a compsci lecture that just introduced karnaugh maps and i’m not sure the professor knows what a gray code is

ta Radvylf srik su shilani

mathcat

oh no

Bgil Midol

6:24 PM

that looks pretty normal to me except the weird pathway

ta Radvylf srik su shilani

Keep in mind it only happens while scrolling

Unrelated String

also he tried to relate the toroidal topology to a space-folding warp drive from a movie he forgot about instead of like

pacman

Bgil Midol

@taRadvylfsriksushilani well then screen tearing

ta Radvylf srik su shilani

Good choice

Bgil Midol

pic of more serious tearing?

Unrelated String

6:27 PM

That’s pretty serious tearing

Bgil Midol

it doesn't look that bad to me

ta Radvylf srik su shilani

6:39 PM

Well it turns out the screen tearing option also disables the ability to change the screen brightness

I'm seriously considering returning this laptop

It's just one annoyance after another

It's not nearly as fast as it should be, it has weird issues with the sound, the display does stupid stuff, the battery life is awful, and so on

I think the however-many-days to return it are up, unfortunately

New Posts

0

Q: Code Golf Birthday Cake

Your task is to print this exact text: 0 2 4 6 8 10 | | | | | | &***********& | Code Golf | | e---------f | | d___________l | | o-------------o | | C_______________G | ###Dennis$Dennis### ##################### Rules Trailing or leading newline is allowed code-golf, so s...

code-golf kolmogorov-complexity

ta Radvylf srik su shilani

It has a three year accidental damage warranty, but I can't really bring myself to drive a tank over a $1k laptop lol

ta Radvylf srik su shilani

6:57 PM

I kinda hate that JS's Sets are ordered

Surely that's got at least some performance impact

emanresu A

7:08 PM

It probably makes lookup simpler tho

ta Radvylf srik su shilani

Wait really?

I figure since it's a hash table it really doesn't matter

So all ordering would do is require more memory

emanresu A

@MichaelSeifert Now I have found a proof that the given solution is optimal. But this comment field is too small to contain it. — kasperd Feb 1 '16 at 18:51

@taRadvylfsriksushilani True, you're probably right

ta Radvylf srik su shilani

It's either going to be a hash table or a BST, anything where ordering is important is going to be like O(n)

pxeger

7:25 PM

????