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Write your challenge just as you would when actually posting it, though you can optionally add a title at the top. You may also add some notes about specific things you would like to clarify before posting it. Other users will help you improve your challenge by rating and discussing it.

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3616 Answers 3616



The original creator of this meme has gone blind, lost his internet and accidentally deleted all his memes. Except this one. He has this one last meme on his desktop, and since he can't see, he wants to know what this meme is.

By hearing it.


Your challenge is to write the shortest program that will produce a playable audio file that the meme creator will play to hear the text in this meme.

  • The input is the meme below
  • The output will be a audio file that reads the output text in English and has a slight pause after a colon or a new line. But don't read out 'colon'

Answer the following questions for your readers.

  • You can use any programming language
  • You can use any existing library
  • Output audio must be playable by vlc
  • Networking is not allowed, you cannot connect to any internet services
  • Shortest answer wins

Input and Output


surprised pikachu eyesight


Me: spends 8 hours per day on the internet

Eyesight: gets worse


  • 7
    \$\begingroup\$ The output would always be hardcoded, so there's no point in the input \$\endgroup\$
    – Jo King Mod
    Mar 8 '19 at 9:43
  • 1
    \$\begingroup\$ This challenge would be nice with different memes as test cases. Otherwise it would be hardcoded as said previously. \$\endgroup\$
    – Belhenix
    Mar 20 '19 at 19:35

Compress briefly

Compress and decompress the first chapter of Worm, beginning with the opening words "Class ended" and ending with the closing words "my best friend." (including the period). You do not need to include any of the formatting (copy and paste as plain text).


  • You may not use any built-in or imported compression functions or procedures. You must implement the compression yourself.

  • You may either write one program to compress and another to decompress, or one program that does both. If you wish, the second option can be a polyglot, where compiling as one language compresses and compiling as the other decompresses.

  • Your program must be no more than 2000 bytes long. You may, at your option, compress your program with bzip2 or gzip before measuring its size for the purpose of meeting this limit.

  • Your program does not need to work for any other text.

  • Standard loopholes apply.

  • Standard I/O rules apply.


  • The score is the sum of the total number of bytes of your program(s) and the total number of bytes in the compressed text.

  • If you use a single program to compress and decompress, then you may have to pay a penalty. Specifically, you must pay a number of bytes equal to the Levenshtein distance between the shell command needed to (compile and) run your compression program and the one needed to run your decompression program. You can calculate this online. A special exception: if you choose to write a polyglot, then you can leave out the paths to the compilers/interpreters when you calculate the penalty.

Tags: code-challenge, compression

  • \$\begingroup\$ Related \$\endgroup\$
    – Beefster
    Mar 19 '19 at 22:31
  • \$\begingroup\$ @Beefster, a bit, but I think there are enough differences to make competitive answers largely incompatible. \$\endgroup\$
    – dfeuer
    Mar 19 '19 at 22:36
  • 2
    \$\begingroup\$ I don't think any answers are going to outperform gzip/bzip/whatever. There's no obvious patterns to exploit in the text. \$\endgroup\$
    – Beefster
    Mar 19 '19 at 22:37
  • 2
    \$\begingroup\$ Also: how is this different from kolmogorov-complexity? \$\endgroup\$
    – Beefster
    Mar 19 '19 at 22:38
  • \$\begingroup\$ @Beefster, it's different because I don't allow the code to be big enough to have much chance of encoding the text in it. It doesn't have to outperform industrial-strength algorithms. That mention had to do with the source code size limit, intended to give extremely verbose languages the opportunity to participate. \$\endgroup\$
    – dfeuer
    Mar 20 '19 at 0:28
  • \$\begingroup\$ Every answer will be some variant of import gzip; gzip.compress(story) \$\endgroup\$
    – Beefster
    Mar 20 '19 at 16:21
  • \$\begingroup\$ @Beefster, is my explicit prohibition of that insufficient? My first rule is that you can't use a built-in or imported compression function. \$\endgroup\$
    – dfeuer
    Mar 20 '19 at 16:42
  • \$\begingroup\$ That sounds a lot more interesting than it actually is. There's a reason "do X without Y" questions have fallen out of favor. Compression challenges are hard to write. At the very least, you need some exploitable pattern common to a class of strings. This simply isn't the case in the linked text. \$\endgroup\$
    – Beefster
    Mar 20 '19 at 19:29
  • \$\begingroup\$ Even without using built-ins the best answer will use some variant of Huffman coding that fits in 2000 bytes. LZ77 is also pretty easy to implement and works well on text. \$\endgroup\$
    – Beefster
    Mar 20 '19 at 19:44

Output an alphabet suite

A successor to the ŋarâþ crîþ alphabet challenge.

Outputting the alphabet song with as few letters as possible was too easy, but what about outputting many of them?

Your challenge is to write as many programs as you can, with no two programs sharing any Unicode codepoints, and each program outputting the names of the letters of the alphabet (or the glyphs of some other kind of phonetic script) used by a different language. For instance, one program can output

a bee cee dee e eff gee aitch i jay kay el em en o pee cue ar ess tee u vee double-u ex wye zed

and another program can output

a be ce de e efe ge hache i jota ka ele eme ene eñe o pe cu erre ese te u uve uve doble equis ye zeta


  • For a given language, there will probably be some leeway in what you can output.
  • Unlike in the previous challenge, you don't need to worry about any particular punctuation. You should at least separate each letter name with whitespace.
  • You must output the names of the letters, not the letters themselves (so A B C... is invalid), unless the letters are literally pronounced so in the language in question.
  • If a language uses both capital and lowercase letters, then you may output the letter names in either case. If it uses only one of them, then you must output the alphabet in that case.
  • You must use a different language's alphabet for each program, but you are allowed to use the same script in the context of different languages.
  • Constructed languages are allowed, as long as they predate the challenge.
  • You may use different programming languages for each program. Or the same.
  • Standard loopholes are forbidden.


  • is the requirement against sharing any codepoints too strict?
  • 2
    \$\begingroup\$ I haven't downvoted you, but suspect that the major reason that you're getting downvoted is that it's totally unclear what outputs are valid or not, and skimming the edges of that is where most of the byte savings are going to come from in a code-golf. That said, I don't think this is code golf, despite having the tag. You'll probably find that, when any golfing aspect is removed, the strings to print are more or less irrelevant, so you might as well use a fixed, objective set of strings instead of the ones you have. \$\endgroup\$ May 13 '19 at 16:24

add two numbers in string representation


Given two strings representing non-negative integers in base 10, return the string corresponding to their sum - without any explicit arithmetic operations. This means you have to implement incrementing (probably with a lookup and indexing) and carrying (probably with iteration or recursion) on your own. Comparisons and boolean operations are allowed.


"1" + "1" = "2"
"5" + "6" = "11"
"0" + "8" = "8"


Write a function or program which takes the two strings in a way you want to.
Output, print or return the solution in whatever way you want.

Ah, and also don't forget that this is code-golf, so shortest answer in bytes will win. Also, all standard loophole rules and so on apply (you should know from all the other challenges!)


This challenge changed, evolved and got compressed during discussion with Adám starting from here (feel free to review the edits and chat of this post on how we got here)

Tags for cgcc post:

  • 9
    \$\begingroup\$ This is still "Do X without Y", and Y is not always clear-cut. What counts as an "explicit arithmetic operation" in lambda calculus? \$\endgroup\$ Jul 25 '19 at 15:22
  • \$\begingroup\$ @PeterTaylor my english is not the best in the world and also i am not a pro in thins like loopholes or coding terminus around maths. you have any idea how to propose this or what kind of operations to prohibit? I would just come up with explicite "+" "-" "*" and "/" operations directly on the string representations (also to exklude languages which can handle interpreting strings as numbers). But are there furter operations I forget? \$\endgroup\$
    – pixma140
    Jul 26 '19 at 5:43
  • 7
    \$\begingroup\$ I don't think it can be fixed. \$\endgroup\$ Jul 26 '19 at 5:53
  • \$\begingroup\$ I agree this can't be defined objectively. The only way I can see this working is if the output was required to include the steps of calculation so that it's no longer an non-observable requirement. That would probably involve specifying a particular approach to implement though. I can't guess whether such a restriction would make the challenge interesting, but I suspect it would not. \$\endgroup\$
    – trichoplax
    Jul 28 '19 at 18:58
  • \$\begingroup\$ Guess then I will better not post this question outside of the sandbox.. But thanks to you all so far! :) \$\endgroup\$
    – pixma140
    Jul 29 '19 at 5:41

The goal is to make a program that is compilable in as many languages as possible.

  • The program must be compilable with a specific compiler version and compiler parameters without any errors.
  • The program may result in an error when run.
  • The source code must not be empty or whitespace.
  • 1
    \$\begingroup\$ This is somewhat similar in spirit but not the same. This probably is a duplicate of something, strictly or less so, but that's the first thing that came to mind \$\endgroup\$ Aug 27 '19 at 7:48
  • 2
    \$\begingroup\$ A null program is compilable in most(if not all) languages. (Including specific compilers of C(in IOCCC).) \$\endgroup\$
    – user85052
    Aug 27 '19 at 10:15
  • \$\begingroup\$ @A_ I've added an additional rule. \$\endgroup\$
    – user11909
    Aug 27 '19 at 10:58
  • 3
    \$\begingroup\$ As-is, this will be closed as Too Broad, since there's no "thing" for the program to do. Have a look at the polyglot tag and see what others have done. \$\endgroup\$ Aug 27 '19 at 14:25
  • \$\begingroup\$ Define "compile". \$\endgroup\$ Aug 28 '19 at 23:23

Writing a WebCrawler


Design a web crawler that recursively extracts all the hyperlinks from the HTML of the web page and does the same for every hyperlinked page it finds. The webcrawler must store the hyperlinks in a separate file

How The WebCrawler Works

First the webcrawler should download the HTML file of the URL the user inputted.

Second the webcrawler will copy every single hyperlink embedded in the hyperlink and paste it into an output text file. The best general way to do this based on my experience is to have the webcrawler iteratively search through the HTML file for an "a href" tag. Be careful about what kind of hyperlinks are embedded in those tags. Sometimes only the subdomain directories of a complete hyperlink are embedded in this

For example: https://en.wikipedia.org/wiki/Toyota may simply have an a href tag in the HTML file of a webpage as: "/wiki/Toyota"

After extracting all the hyperlinks of the first webpage, visit all the hyperlinks found on the base webpage starting from the the first hyperlink found and repeat all the steps above. The only exception to doing this is obviously if the hyperlink fails to lead to an HTML page.


The program must accept only one URL as input.


A text file that lists every hyperlink that it finds. Note:

Your webcrawler must avoid revisiting webpages it has already crawled. This can cause the crawler get trapped in a "circular link loop" where it continously visits the same pages endlessly.


Special consideration will be given to submissions that prove they are capable of crawling deep web websites, including those with the .onion sites.


Create a "Transpiler"

for the purpose of this challenge, a transpiler is any program that takes valid source code from one language as input and produces a program valid in another language that performs the same actions. Calling the original languages interpreter is not banned.

Posts should start with "SRCLANG to DSTLANG in LANG; X bytes" as a heading.

Here's an example post:

Shell to Ruby in Ruby; 41 bytes

puts'`bash #{Data}`

Here we use the somewhat obscure Data constant to embed arbitrary data in the program. this has the advantage of never having to escape anything.

Each "triple" of source, destination, and working language represents its own category, as this challenge varies greatly in difficulty depending on the languages used.

  • \$\begingroup\$ What is the winning criterion? Are there requirements for the languages used? \$\endgroup\$ Nov 6 '20 at 23:09
  • \$\begingroup\$ @RedwolfPrograms lowest byte count, as usual. I guess no strict subsets as well, so you can't say cat is a sh to bash transpiler \$\endgroup\$
    – binarycat
    Nov 6 '20 at 23:24
  • \$\begingroup\$ How would this be consistently graded? I don't get how this is fair to all answers. \$\endgroup\$
    – Razetime
    Nov 7 '20 at 3:35
  • \$\begingroup\$ Is g++ a C++ to x86 assembly transpiler? "this challenge varies greatly in difficulty depending on the languages used" I'd say it varies in difficulty way too much. \$\endgroup\$ Nov 7 '20 at 7:08
  • \$\begingroup\$ @thedefault. Yes, but it's far from trivial. As for variation, like I said, each "triple" of languages forms it's own category. If it's necessary to have 1 winner, I guess it could be popularity-contest. \$\endgroup\$
    – binarycat
    Nov 8 '20 at 21:35

I have the following code. Help me make it code shorter.

new Promise(r=>r(URL.createObjectURL(new Blob(['<h1>Example</h1>'],{type:'text/html'})))).then(u=>open(u)&&setTimeout(t=>URL.revokeObjectURL(u),2e3))

The Catch:

  • This has to be in JavaScript
  • It cannot contain semicolons
  • It must be a "one-liner"
  • It must have the same steps as the code above:
    1. Create a blob URL from a blob
    2. Open a browser window of the blob URL
    3. Revoke the blob URL


  • The winner will be decided by the shortest amount of bytes
  • If you try this in another language, you will still get an upvote

Most digits of Pi in a hundred bytes

  • 4
    \$\begingroup\$ It's likely possible to output infinitely many. \$\endgroup\$ Jan 19 '21 at 3:09
  • \$\begingroup\$ @thedefault. how? \$\endgroup\$
    – someone
    Jan 20 '21 at 0:46
  • 2
    \$\begingroup\$ By using one of the many known formulas for pi. And if you do not use a formula for pi, you're compressing random digits (it's possible to store around 240 digits like this). codegolf.stackexchange.com/q/47808 has multiple answers below 100 bytes. \$\endgroup\$ Jan 20 '21 at 1:52

Reinvent math

The task is simple. Define the basic operators (+, -, *, /) without using them directly.

Also banned:

  • any add-assign (+=) and its equivalents
  • basically anything intended to be used as a basic arithmetic operation

Program should consist of at least 4 binary functions, one for each operation. they may call other functions defined in your program, including each other. The types of the arguments to the function may be any types that the basic arithmetic operators work on, except for types that are less than 3 bits in size.

Shortest code wins

  • \$\begingroup\$ Thank you for using the sandbox. Have you considered stating the required argument domain? And how should one answer? Using for functions/programs with the total length being the score? Can the four share code? \$\endgroup\$
    – Adám
    Feb 8 '21 at 19:35
  • \$\begingroup\$ Also, what does "using them directly" mean? Does that mean we can't use those four symbols or their equivalents in whatever language we use? And do we implement them for integers or floating-point numbers? \$\endgroup\$
    – user
    Feb 8 '21 at 19:43
  • 1
    \$\begingroup\$ If our language allows e.g. using _plus_ instead of +, is that allowed? \$\endgroup\$
    – Adám
    Feb 8 '21 at 19:45
  • \$\begingroup\$ @user I feel like it it's fairly clear what "using them directly" means. I can't really think of an alternative interpretation. Any numeric type which the basic operators work on will do. For most c-derived languages, this will be floats and ints. \$\endgroup\$
    – binarycat
    Feb 8 '21 at 19:54
  • \$\begingroup\$ @binarycat It's not clear to me - I can't tell if you're talking about those four specific symbols or the equivalent operators in the answer's language (if there is an equivalent operator). Also, could you add to the draft that any numeric type will do? \$\endgroup\$
    – user
    Feb 8 '21 at 19:57
  • 1
    \$\begingroup\$ Are we allowed to use the basic operators in each others' definitions, e.g. plus(x,y)=x--y? \$\endgroup\$
    – Adám
    Feb 8 '21 at 20:15
  • \$\begingroup\$ @Adám Ideally, the operator will behave the same as the builtin, but if that's not possible due to restrictions in the language, that's ok. Also, no _plus_ wouln't be allowed. That is still using the basic operator of addition. \$\endgroup\$
    – binarycat
    Feb 8 '21 at 20:19
  • \$\begingroup\$ @binarycat OK, that's useful information (i.e. it should be included in the challenge specification). \$\endgroup\$
    – Adám
    Feb 8 '21 at 20:29
  • \$\begingroup\$ Are we allowed to use the corresponding operations in a different language than the one we're answering in, i.e. to call out? \$\endgroup\$
    – Adám
    Feb 8 '21 at 20:31
  • \$\begingroup\$ Pro-tip: I note that you have never posted any challenges. restricted-source challenges are notoriously difficult to get right. I'm not saying this is a bad challenge, not at all, but I highly recommend posting a few well-received standard code-golf challenges before attempting a restricted-source one. \$\endgroup\$
    – Adám
    Feb 8 '21 at 20:33
  • \$\begingroup\$ @Adám the post has been updated to reflect the fact that the answer is no \$\endgroup\$
    – binarycat
    Feb 8 '21 at 20:34
  • \$\begingroup\$ @Adám It's really not restricted source, just the "no using a builtin that does exactly what the challange says" loophole. \$\endgroup\$
    – binarycat
    Feb 8 '21 at 20:36
  • 5
    \$\begingroup\$ This is a textbook example of a "do X without Y" challenge and simply isn't considered interesting on this site. \$\endgroup\$
    – Beefster
    Feb 8 '21 at 20:48
  • 2
    \$\begingroup\$ @binarycat You seem very convinced that this isn't do-X-without-Y. I'd be very interested in hearing why you think so, especially considering that your text literally says "Define [=do] the basic operators (+, -, *, /) [=X] without using them directly [=Y]." \$\endgroup\$
    – Adám
    Feb 8 '21 at 21:47
  • 1
    \$\begingroup\$ Essentially a duplicate of Add without addition, as the same techniques can be used to define all four operators. \$\endgroup\$
    – Bubbler
    Feb 8 '21 at 22:54

Google search

Challenge is very simple, you have to get a string as input and then launch the default web browser, and search for that string in Google.

Input string will have only characters a-zA-Z

Google search URL is google.com/search?q=querystring

Standard loopholes apply, Internet connection allowed, but only to google.com domain

Tags: ,

Author note: challenge title sucks, please improve it!

  • 1
    \$\begingroup\$ I suspect on many (older) systems the notion of a default browser does not exist. In addition, I think there are many other escape characters. Of course, you could allow the answers to fail - but without the encoding requirements this is probably a dupe of some old basic internet challenge. \$\endgroup\$ Feb 20 '21 at 18:08
  • 1
    \$\begingroup\$ Also, %20 is not the right escape sequence for a + \$\endgroup\$
    – pxeger
    Feb 20 '21 at 19:00
  • \$\begingroup\$ @FryAmTheEggman The first one is not really an issue, if the programming language doesn't have the thing then it can't have an answer. \$\endgroup\$
    Feb 24 '21 at 3:55
  • \$\begingroup\$ For the challenge: it's best to specify which characters might appear in the input. \$\endgroup\$
    Feb 24 '21 at 3:56
  • \$\begingroup\$ @FryAmTheEggman,user202729 edited, now input will only have a-zA-Z \$\endgroup\$
    – wasif
    Feb 24 '21 at 17:30
  • \$\begingroup\$ Most languages can't launch a browser. Also, there are dozens like this already, \$\endgroup\$
    – emanresu A
    Feb 25 '21 at 4:04
  • \$\begingroup\$ Sorry, I missed your edit earlier. I think if you want to go ahead with this you need to define what the "default browser" is, and what to do if it isn't present. Depending on how you define it, this may not be a dupe, but I imagine you will have some trouble with different systems defining it differently. \$\endgroup\$ Mar 3 '21 at 19:03

Reverse error quine


Based on this

Write a quine that prints it own source code in reverse, but to STDERR.


  • +200 using other files I.E. reverse.txt
  • +150 internet usage
  • +100 reading own source code


  • Minimum length of source is 2 bytes

  • Standard loopholes apply

, shortest code wins

  • 3
    \$\begingroup\$ As a reverse error quine, it will probably just be basically the same as a plain error quine, but with the creative solutions using syntax errors not valid. The things with penalties should probablly just be disallowed or someone will just do sh, 6 bytes + 20 penalty, tac $0. You can also add [tag:quine] \$\endgroup\$ Feb 24 '21 at 17:45
  • 4
    \$\begingroup\$ But thanks for using the sandbox! \$\endgroup\$ Feb 24 '21 at 17:46
  • \$\begingroup\$ Why the rule No palindromes? Aside from Stack Cats, there are pretty much no languages that print a palindromic error. \$\endgroup\$
    – emanresu A
    Feb 25 '21 at 4:07
  • \$\begingroup\$ Changed the rules: 1) Increased penalty (None will not now dare to read own source code) 2) Palindromes allowed 3) Added the tag quine \$\endgroup\$
    – user101036
    Feb 25 '21 at 7:45
  • \$\begingroup\$ Penalty in code golf is discouraged by itself, just like bonuses. Accessing the internet/other files/the source file itself to get the desired output is already considered a standard loophole, so you should just say they're not allowed, and remove the penalties altogether. \$\endgroup\$
    – Bubbler
    Feb 25 '21 at 8:06
  • \$\begingroup\$ Also, another thing to avoid: using old challenges as a model. \$\endgroup\$
    – Bubbler
    Feb 25 '21 at 8:11

“Simple” Programming Homework

Your friend has been caught sleeping in class again! As punishment, his computer science teacher has assigned him homework, knowing that he will not be able to solve it due to not having paid any attention.

The assignment seems deceiving simple at first; all that is required is to output the string:

John Doe

Unfortunately, the teacher is intent on making the simple assignment much more difficult. Since your friend was not listening when the teacher explained the concept of strings and numbers, the teacher forbids him from using any number character (0-9) or the quotes (", ', `).

Can you help your friend solve this problem with the shortest code possible, and save his computer science grade in the process?

Try to find the shortest code in each language!

Note: it is encouraged to try to solve this problem in languages where string/character literals exist but cannot be used due to the restrictions (most mainstream languages are like this, e.g. C++).

  • \$\begingroup\$ Better leaving it here for a while (and ask in chat often) to see if people mostly agree that what "literal" means is obvious. (see, bash have echo John Doe and BF has +++something+++., and most languages doesn't have a formal specification to define English names for the components of the language) \$\endgroup\$
    Feb 27 '21 at 12:18
  • \$\begingroup\$ Other than that (huge) point it is clear enough. [please review other sandbox posts] \$\endgroup\$
    Feb 27 '21 at 12:19
  • \$\begingroup\$ @user202729 Ask which chat? \$\endgroup\$
    – user101295
    Feb 27 '21 at 22:14
  • \$\begingroup\$ @user202729 I thought this would be interesting for most languages that do use quotes for string and character literals like C, but I do see how it might be too easy in some languages. \$\endgroup\$
    – user101295
    Feb 27 '21 at 22:54
  • 1
    \$\begingroup\$ chat.stackexchange.com/rooms/240/the-nineteenth-byte \$\endgroup\$
    Feb 28 '21 at 6:13

Geometry Dash Clone in a weird Way?

Try to make a functional clone of Geometry Dash in the shortest time.

How GD Works.

  • You have a cube. In the clone, it can be as small as you want, but no bigger than 2x2.
  • You have to jump over spikes. The key to do this is (preferably) the up arrow key, but can be any option you want (simply tell me in your answer what key is it.
  • If you touch the spikes, the screen says "Game Over." and exits in 3 seconds.
  • There are blocks! You can jump on them, but touching them from the left side results in the same thing that happens if you touch the spikes.
  • A song plays in the background. How you do this is up to you.


  1. 3 Extra points for working forwards and backwards.
  2. Must have the letter a 5-7 times and no q at all!
  3. Allows ascii art type output and text input (standard input)!

Sandbox Questions

How is this even going to work?

  • \$\begingroup\$ Welcome to codegolf! I don’t really recommand to compare how fast submit time after question release, since there maybe someone out there already holding an answer, and it also really timezone dependent. \$\endgroup\$
    – okie
    Dec 2 '21 at 5:41
  • \$\begingroup\$ But it could be one of the code-golf problem, and allowing ascii art type output and text input (standard input) could allow more language to compete. \$\endgroup\$
    – okie
    Dec 2 '21 at 5:42
  • \$\begingroup\$ also the flawless limit is kinda weird, extra point for certain language is not suggested, if you still want to give extra point, you may want to say how much extra point is. \$\endgroup\$
    – okie
    Dec 2 '21 at 5:48

Find the square of a number without using the multiplication sign or division sign

e.g. "/" "//" "*" "**" are not allowed

no imports are allowed either

An integer will be given in the input

Test cases:

5 -> 25

6 -> 36

10 -> 10

724 -> 524176

  • \$\begingroup\$ Can you add test cases and information? \$\endgroup\$
    – Fmbalbuena
    Jan 10 at 10:07
  • \$\begingroup\$ added accordingly fmbalbuena \$\endgroup\$
    – DialFrost
    Jan 10 at 10:10
  • \$\begingroup\$ Are we allowed to use * if it doesn't mean multiplication? \$\endgroup\$
    – Adám
    Jan 10 at 10:25
  • \$\begingroup\$ If our language has "square" as a built-in, can we use it? \$\endgroup\$
    – Adám
    Jan 10 at 10:32
  • \$\begingroup\$ that's interesting code challange, but i think it's easily bypassed by some esolang like vyxal that is using ² as square, you can try disabling square or multiply function, so that people don't just simply use other symbol to complete the task \$\endgroup\$
    – okie
    Jan 10 at 23:45
  • \$\begingroup\$ May I use character if it is the operator or keyword for multiplication in my language? \$\endgroup\$
    – tsh
    Jan 11 at 6:53

Output the number of lines of your code

Your task is to write a program that counts the number of its lines of code and outputs them.


  • The number mustn't be hardcoded into the program, nor in any other external resource;

  • Internet access is forbidden;

  • Your program's output must be the number of lines only;

  • Your program should not use any tool, macro, function, or similar device designed with the specific purpose of counting lines.

  • 2
    \$\begingroup\$ I don't see much of a challenge here. wc -l $0? \$\endgroup\$
    – ugoren
    Feb 23 '14 at 17:15
  • 1
    \$\begingroup\$ It can be a nice question, but needs some work. Just add something like "it should not use any tool, macro, function, or similar device designed with the specific purpose of counting lines". \$\endgroup\$ Feb 24 '14 at 2:10
  • \$\begingroup\$ @Victor Nice point, added. Thank you :) \$\endgroup\$
    – Vereos
    Feb 24 '14 at 10:10
  • 4
    \$\begingroup\$ As long as you can read the program file, it's no challenge. E.g. print len(l for l in sys.argv[0]). But if you forbid reading the source, and forbid hard-coding the length, what's left? \$\endgroup\$
    – ugoren
    Feb 24 '14 at 14:00
  • \$\begingroup\$ @ugoren I don't see where it says it can't read its source. \$\endgroup\$
    – user10766
    Feb 27 '14 at 22:13
  • 1
    \$\begingroup\$ @user2509848, It doesn't. This is why the question is easy and uninteresting. \$\endgroup\$
    – ugoren
    Feb 28 '14 at 5:56
  • \$\begingroup\$ @ugoren If you can't though, how will you tell, hardcode it? \$\endgroup\$
    – user10766
    Feb 28 '14 at 5:57
  • 1
    \$\begingroup\$ @user2509848, Either way, not a good question. \$\endgroup\$
    – ugoren
    Feb 28 '14 at 6:25
  • 2
    \$\begingroup\$ This is one byte in any golfing language with implicit output: 1 \$\endgroup\$
    – Nic
    May 9 '16 at 20:11

Here is my first attempt at a cops and robbers post (which is why I'm using the sandbox).

Cops - Golfed recursion

You must select a language that satisfies the following criteria:

  • Functions - It must be possible to create a function with any number of integer input values and a single integer output (or return) value. The function may also be a complete program in itself. (Your language may not call it a function, but that is ok)
  • Arithmetic operations - The integer operations +-*/% should all be possible, either in a simple or a complicated manner.
  • Data - You should be able to store one-byte or two-byte long integers (either signed or unsigned will do). You may do this also in an indirect manner.
  • Iteration - You must be able to create a loop that will keep running until a condition is satisfied. Therefore < > = <= >= ! & | should also be supported, either directly or indirectly.
  • Recursion - You should be able to call a function from within the function itself with a set of input values calculated by the main function.
  • Declaration - You should be able to declare new integer variables as needed from within the function.


You need to create a recursive function. Code will be scored by the number of characters in it, the shorter the better. A solved code cannot win the challenge. A post with less than 5 up-votes cannot win the challenge. There will be no overall winner, but a separate winner for each language.

Robbers - Golfed recursion

Your objective is to pick up a cop's post, and write a function in the same language but it should not use any recursion (can use iteration). The function may create any number of variables, loops, etc. but should be able to achieve the exact same end result (atleast, in theory) as the cop's one.

Your score will be the same as the cop's post's score at the time it was solved. His/her post is now invalid, and you get his/her score

  • 2
    \$\begingroup\$ I don't understand how a cop can write an answer that isn't going to be cracked, unless the language of choice can only loop via recursion (which I think you're trying to rule out by requiring that "iteration" must be possible). Also, requiring 5 votes to be a winner is only encouraging tactical voting. Answers that are actually invalid will likely get downvoted and deleted anyway. \$\endgroup\$ Feb 10 '16 at 12:36
  • \$\begingroup\$ @MartinBüttner Maybe in some languages it is possible by exploiting both closure and recursion, but I mainly agree with your point: recursion and iteration are two ways to do the same thing. \$\endgroup\$
    – Katenkyo
    Feb 10 '16 at 12:41

Your task is to create a program that outputs a random pizza recipe following this one rule:

No random number choosers, you may have random text choosers. All standard code-golf rules apply. A sample output:

A simple PEPPARONI pizza sprinkled with fish and sausages. Your program must have the following items:

  • Anchovies
  • Fish
  • An adjective for the pizza

The program written with the shortest code wins.


The winner shall be picked on April 3rd, 12AM on the time zone GMT+3.

  • \$\begingroup\$ I already had an answer to the question, albeit non-competing: Python3 print("Have a plain MARGHERITA without any",["fish.","anchovies."][len(input("What's your favourite pizza? "))%2]) \$\endgroup\$
    – mIllIbyte
    Mar 31 '16 at 12:41
  • 5
    \$\begingroup\$ Uh, this has a lot of problems with clarity. First, all "random text choosers" are implemented with "random number choosers" which makes this restriction feel a bit bizarre. Second, what counts as an adjective for pizza? And since this is code golf, people will always pick the shortest available. And third, what should an output look like? It's not clear from the spec. Also, sort of unrelated, but usually putting a time limit is unnecessary, even extremely popular challenges stop getting responses with any frequency after a month or so. \$\endgroup\$ Mar 31 '16 at 12:59
  • \$\begingroup\$ Did you misspell it on purpose? \$\endgroup\$ Mar 31 '16 at 13:55

What about one question on numeric solve?

Write one function that gets as one argument one function f(x), and one interval a..b and return the list of all element v such f(v)=0 in the interval a..b. In the interval a..b the f must be definite and can not be f(r) = +oo for r in a..b.

Win the one write the function with biggest set of right results. If two have the same set, win the one has less characters. You can not use solve() or nsolve() or fsolve() or one already written function that your sys offer that finds numerical x in f(x)=0

  • 2
    \$\begingroup\$ Finding all zeros of an arbitrary function is impossible unless the domain is restricted. \$\endgroup\$
    – user45941
    Nov 29 '16 at 8:59
  • \$\begingroup\$ Ok you are right \$\endgroup\$
    – user58988
    Nov 30 '16 at 10:04
  • 3
    \$\begingroup\$ The edit doesn't do anything to fix the problem. \$\endgroup\$ Nov 30 '16 at 14:48
  • 3
    \$\begingroup\$ The bigger problem is that this post is incomprehensible. \$\endgroup\$
    – user45941
    Dec 2 '16 at 8:54

Beep. Boop. Maggot?

  1. Read input from STDIN until enter is pressed.
  2. If the input is "Beep", continue.
  3. Otherwise, print "Wrong!" and exit.
  4. Repeat steps one to three with "Boop" instead.
  5. Execute step one.
  6. If the input is "Maggot", output "Done".
    • Otherwise, output "Wrong.".

Remove punctuation (?.!'"), ignore capitalization (a-zA-Z only), and strip whitespace (\t and )

Notes: You must print the text word-for-word, character-for-character. Step 3 is Wrong!, while Step 6 is Wrong.


  • Notice how boop is just beep with the o's turned into e's.
  • There is lots of repetition here, but with many caveats.
  • \$\begingroup\$ Technically speaking, step 4 should repeat steps 1-3, shouldn't it? Anyway, apart from that, I don't see anything technically wrong with the challenge, but I'm not sure it's a very good challenge. \$\endgroup\$
    – user62131
    Jan 1 '17 at 0:07

Score Your Language

I believe that each language has a score. The way you find the score of a language is shown in the ungolfed Python program below

def scorer(lang):

    num = 0

    for i in str(lang):
        num += ord(i)

    return num

Basically the score is the total of the unicode values of the language name.

Now this seemed like a fairly trivial challange, so I thought I'd make it a bit more difficult. You aren't allowed to use your language name (case-sensitive) in the code. So this code in C++ would be invalid as I've used C++ in the code.

#include <iostream>

int main() {

    int total = 0;
    std::string s("C++");

    for (char & c : s) {
        total = total + (int)c;
        c = '*';

    std::cout << total;


Although this does output the required number (153) it is still invalid.


  • You aren't allowed to use the language name but are allowed to use it in a different case. E.g. Java isn't allowed but java is.
  • This is a code-golf so shortest answer in bytes wins
  • You are allowed to use hex/octal codes in strings e.g \150 can be used instead of h
  • Your program must take no input or function arguments
  • You cannot simply output the score. Theoretically the program should work for any language name when changed.
  • Languages where the only valid syntax is the name, such as Chicken are allowed to use said name.
  • Version shouldn't be included so Python is always Python not Python 2 or 3
  • The score is the value of the case-sensitive name

Correct Scores

Language              Score

ArnoldC                675
brainfuck              949
C                       67
C++                    153
Java                   386
Lua                    290
Mornington Crescent   1922
Python                 642
TrumpScript           1165
Vim                    300

Sandbox Questions

1) Why has this been downvoted?

2) I am thinking about putting a reputation limitation so that bosses like Dennis and Martin Büttner can't take answers from people who aren't as accomplished. Is this unfair? Should I not?

3) Is this a duplicate? I couldn't believe it wasn't already taken.

  • 4
    \$\begingroup\$ Terms like "you cannot use your language name" and "it must be calculated by the program" are not only unclear but will likely not be able to be made rigorous. \$\endgroup\$
    – Wheat Wizard Mod
    Feb 5 '17 at 14:58
  • \$\begingroup\$ Are you suggesting that I remove those rules? \$\endgroup\$
    – user63571
    Feb 5 '17 at 15:00
  • \$\begingroup\$ I don't think that the challenge is very interesting without the rules, but I don't think it is clear with them. I would suggest reworking the rules in some manner but exactly how I do not know. \$\endgroup\$
    – Wheat Wizard Mod
    Feb 5 '17 at 15:01
  • \$\begingroup\$ 1. I would guess that it's mainly because it fails some of the tests in Things to avoid when writing challenges (X without Y, asking for different things in different languages, unnecessary fluff, explicitly disadvantaging certain languages, arguably one or two more), although it might also in part be because some people oppose trivial "challenges", and in part because the problems WW mentioned can't be fixed. 2. Very bad idea. 3. It's a multi-dupe: it combines two trivial tasks, each of which independently would clearly be a duplicate. \$\endgroup\$ Feb 6 '17 at 9:15

Popularly print the input


Write a program or function in a language of your choice that takes input and outputs that exact input.


  • Your program/function should output the exact input in any reasonable way.
  • Your program does not have to end after printing the input. It may end up in an infinite loop if you wish, as long as that loop doesn't output any extraneous characters.


The winning answer will be the one that has the highest score. Voters should look for answers that use an unique way to print the input, have a special source code or use neat language features.

  • \$\begingroup\$ Plain "do X in a creative way" popularity contests have fallen out of favour and will likely immediately get closed as being too broad or not having an objective winning criterion. \$\endgroup\$ Apr 4 '17 at 18:33
  • \$\begingroup\$ @MartinEnder: Yeah, I noticed. How do you think I should change the challenge so that it won't be closed? \$\endgroup\$
    – Luke
    Apr 4 '17 at 18:35
  • 1
    \$\begingroup\$ Can't really help you there. If I knew of a good way to make popularity contests work, I'd write some myself. ;) \$\endgroup\$ Apr 4 '17 at 18:39
  • \$\begingroup\$ Probably a duplicate of codegolf.stackexchange.com/q/62230/34718 \$\endgroup\$
    – mbomb007
    Apr 4 '17 at 18:43
  • \$\begingroup\$ @mbomb007: No, this is not a code-golf challenge. \$\endgroup\$
    – Luke
    Apr 4 '17 at 18:54
  • \$\begingroup\$ But there's nothing separating the answers this might receive. Please read this: codegolf.stackexchange.com/tags/popularity-contest/info \$\endgroup\$
    – mbomb007
    Apr 4 '17 at 18:57

Make a Login Screen

Challenge: make code that asks the user to enter a username and password. The username and password should be hard coded, but they must not be visible: you cannot have the entire username or the entire password in plain text in the code. Both the username and the password must be 8 characters long. Upon the incorrect username or password, some error should be displayed. It would be good if there are multiple "accounts" that would display different text on login. The password field should not be visible (Only asterisks or something).

This is Code-Golf, Shortest answer wins.

Standard loopholes are forbidden.

  • \$\begingroup\$ you can't say that answer doing something "would be good" if the shortest answer wins \$\endgroup\$ Apr 18 '17 at 7:05
  • \$\begingroup\$ underhanded challenges are off-topic. \$\endgroup\$ Apr 18 '17 at 8:36
  • \$\begingroup\$ It's not underhanded. \$\endgroup\$ Apr 18 '17 at 14:15
  • \$\begingroup\$ I'm sure this might be a dupe of an obfuscation challenge \$\endgroup\$
    – Beta Decay
    Apr 18 '17 at 23:36

Of numbers of letters

there is something special the number 4. When spelled in English the word 'four' uses exactly 4 letters. I wonder whether there are further such numbers Your task is to identify whether there exist further such numbers and output them in any human readable format. To make this more of a challenge you can do the task in any regional Language of your choice (Say Russian or Portuguese or Spanish or Mandarin or Hindi etc.).

The Best entry will be selected by the most number of such numbers regardless of language used

Best of Luck


No strings code bowling

I created this challenege idea with @redwolfprograms. In the challenge, you would create the longest program possible (code-bowling) it can do anything, but it cannot:

  • Contain any strings, or quotation marks/apostrophes/backticks
  • Contain the same alphanumeric byte more than twice
  • Conatin the same non alphanumeric byte more than three times
  • 2
    \$\begingroup\$ What is the task we have to solve? Is it really alphanumeric character but non alphanumeric byte? \$\endgroup\$
    – Dennis
    Apr 17 '18 at 13:50
  • \$\begingroup\$ Why do you mix characters and bytes? \$\endgroup\$
    Apr 17 '18 at 14:01
  • \$\begingroup\$ I feel like there are a lot of languages that would score the maximum (768) by not (strictly speaking) having alphanumeric characters, and then just wrapping everything in a string: "[3x each other byte value]"". \$\endgroup\$ Apr 17 '18 at 14:08
  • \$\begingroup\$ I think you got bytes and characters mixed up. Both should be bytes, and make sure you specify the program can do anything. \$\endgroup\$ Apr 17 '18 at 14:26
  • \$\begingroup\$ People, the point of the sandbox is to add suggestions. This question has been downvoted several times. Why? \$\endgroup\$ Apr 17 '18 at 22:39
  • 4
    \$\begingroup\$ @RedwolfPrograms downvotes are a way for people to say that this challenge in the current state shouldn't be posted to main. If the challenge gets changed enough to make it viable and interesting the downvotes will be reverted (or upvotes from other people will outweigh them). \$\endgroup\$
    – Leo
    Apr 18 '18 at 1:32
  • \$\begingroup\$ Maybe this challenge should have a "No strings" rule? \$\endgroup\$ Apr 18 '18 at 1:59
  • \$\begingroup\$ Not being able to use e is not really that much of a big deal. Even in C you can get around it easily. (It would prevent you from returning values from functions, but you could just use pass by reference instead.) So that restriction wouldn't really add much to the challenge. \$\endgroup\$
    – N. Virgo
    Apr 18 '18 at 8:35
  • \$\begingroup\$ Now that strings are forbidden, one could just create a huge variable whose name is all the alphanumeric characters twice. This is the bane of any longes code that... challenge. Consider adding some more interesting restrictions. \$\endgroup\$ Apr 18 '18 at 14:35

[Posted, but reference kept]

Given a function with boolean inputs a1, ..., an and a boolean output, output an array of numbers 0 to n satisfying:

For each item in the truth value, if (from the array you output, we repeatedly remove two adjacent numbers x and y satisfying that, for each integer n between x+0.5 and y+0.5, an=1), we can get an empty result array iff the given function's output is 1. You can assume the result exist.

Sample input:

a[1] a[2] result
0    0    0
0    1    0
1    0    0
1    1    1

Sample output: 0 2

Sample input:

a[1] a[2] result
0    0    0
0    1    1
1    0    1
1    1    1

Sample output: 0 1 2 0 1 2

Sample input:

a[1] a[2] result
0    0    1
0    1    1
1    0    1
1    1    1

Sample output: (empty)

shortest code win, but optimizing running time and result length is encouraged(I won't accept but I may upvote)

You may check your answer here

  • 1
    \$\begingroup\$ The spec makes absolutely no sense to me. What does it mean to remove a number from a truth table? \$\endgroup\$ Apr 25 '18 at 12:13
  • 2
    \$\begingroup\$ Still makes no sense. Maybe if you give a detailed worked example I would be able to reverse engineer the spec and propose some changes to the wording. \$\endgroup\$ Apr 25 '18 at 14:59

Write a function that takes compares each pair of adjacent items and swaps them if they are in the wrong order. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted.

Static visualization of bubble sort and a gif explanation.

Bubble sort explanation Bubble sort gif

The steps go from left to right. At each stage, an exchange is made. The darkest color has the most value and finds its final place (bottom) first.

The rules

  • The function must take a list of integers that shall be sorted (less than 20 elements)

  • The function must print each step of the sort.

  • Yes, built-in Bubble sort algorithms are permitted.

  • No, you can not assume only positive integers or unique integers.

  • It's so the shortest code wins!

Test cases

input list
5 4 3 1 2
1 2 3 5 4
11 4 2 1 5


Add an interpreter so the submission can be tested. It is allowed to write this interpreter yourself for a previously unimplemented language.


It's my first code-golf idea I'm fully open to improving it with more experienced users if I missed something.

This is not a duplicate of Bubble sorting in progress.

Thanks to @Erik the Outgolfer for encouraging me to post my idea in the sandbox.

  • 3
    \$\begingroup\$ Can you add one walked-through example? I.e. show each pass. \$\endgroup\$
    – Adám
    Jun 20 '18 at 13:04
  • \$\begingroup\$ You note it isn't a duplicate of the in-progress bubble sort, but what distinguishes it from Golf me a bubble sort, which was closed as a dupe of that? \$\endgroup\$
    – Geobits
    Jun 20 '18 at 13:10
  • \$\begingroup\$ @Geobits This was not a dup but unclear. \$\endgroup\$
    – DIDIx13
    Jun 20 '18 at 13:12
  • \$\begingroup\$ Here's my c# non-golfed solution : dotnetfiddle.net/ZFkl5y \$\endgroup\$
    – DIDIx13
    Jun 20 '18 at 14:01
  • 7
    \$\begingroup\$ You claim it's not a duplicate of codegolf.stackexchange.com/q/92753 but you don't adduce any argument to support that claim, and I can't see any significant difference. (The upper limit is a trivial difference IMO). \$\endgroup\$ Jun 21 '18 at 6:14

Once, I thought of this. Rules:

1: You must make a fractal that looks like the specified thing.

2: One thing per round.

3: Algorithms are rated by two scores: Resemblance and Compactness. The one that gets the highest scores wins!

4: Only I can tell what thing must be made.

5: Only one entry per user. Do not plagiarize.

6: One may code in anything they wish.

7: Have fun!

Round 1: Squidward's head!

  • \$\begingroup\$ Erchh! OK OK Remove the PM stufs. didnt know \$\endgroup\$
    – Ikura
    Jul 31 '18 at 0:12
  • 2
    \$\begingroup\$ On this site, winning criteria has to be objectively defined. (by tradition, I have to admit... there is popularity-contest (read the tag info page for more details), but if you really want to make a pop-con, be careful) "Resemblance" is quite... subjective, unless you can define an objective formula. Also, what is a fractal exactly? \$\endgroup\$
    Jul 31 '18 at 4:05
  • \$\begingroup\$ For example, how many points would I score if I just made the initial fractal look like the image and have it spiral inwards? What is the objective formula of Compactness/Resemblance \$\endgroup\$
    – Jo King Mod
    Jul 31 '18 at 6:04
  • \$\begingroup\$ A fractal is a shape that recurses. It has copies of itself in it. Analyze the Mandelbrot set, you'll see mandelbrots in mandelbrots. What is a pop-con? Sounds like a soda convention. I'd love to go there! JK \$\endgroup\$
    – Ikura
    Jul 31 '18 at 14:32
  • 1
    \$\begingroup\$ @user202729, experts are unable to agree on the definition of a fractal. That aside, this looks more like a forum game than a good fit for this site. \$\endgroup\$ Jul 31 '18 at 14:46
  • \$\begingroup\$ Oh, popularity? No. No voting. I will work on my formula, with a new parameter: Mandelbrottiness, which is more or less Goldilocks. \$\endgroup\$
    – Ikura
    Jul 31 '18 at 14:54
  • \$\begingroup\$ I attempted doing this on Encyclopedia Spongebobia, then went here. \$\endgroup\$
    – Ikura
    Jul 31 '18 at 14:55
  • \$\begingroup\$ Then maybe a Stack Exchange for off-topic? \$\endgroup\$
    – Ikura
    Jul 31 '18 at 14:57
  • \$\begingroup\$ @Ikura There are no such SE site, because it would generate low-quality content. Try Quora or Reddit... \$\endgroup\$
    Jul 31 '18 at 15:15
  • \$\begingroup\$ Ergo! Goin' to the Kongregate Off-topic forum! \$\endgroup\$
    – Ikura
    Jul 31 '18 at 18:48

This question is a simplified description of the requirement described at Permutations to the nines

Given input integer (minimum) where the first digit is always 1 and the adjacent digits are increasing in value, e.g.,





with the ability to handle up to the integer


where the maximum integer is always the input integer in reverse order, e.g.,







Return a list (array) of each number between the input minimum and maximum integer which satisfies three conditions

  1. the resulting integer list item includes only the individual numbers comprising the input number
  2. the resulting integer list item does not contain any duplicate individual digits
  3. the resulting integer list item is greater than the preceding integer list item and not greater than a following integer in the list

Test cases

Valid list items

12 -> [21] // done

123 -> [132,213,231,213,312,321] // done

Invalid list items

12345 -> 12344 // contains duplicate digits in whole number

123456789 -> 13256789 // not the next integer by increasing numeric value order

123456789 -> 987654322 // greater than maximum integer and duplicate digits

Winning criteria

The algorithm which uses the least amount of operations to compute the complete resulting list of items.


123 -> 123+5+4=132 // two mathematical computations

123 -> 123+9=132 // one mathematical computation (winning criteria)

(@JoKing suggested fastest-algorithm tag; math and code-challenge tags are also applicable)

  • \$\begingroup\$ @PeterTaylor Pared down version of the original question. \$\endgroup\$ Oct 8 '18 at 18:30
  • \$\begingroup\$ Am not as yet well-versed in Big-O notation. If the phrase "the least amount of operations to compute the complete resulting list of items" can be translated into Big-O notation, kindly suggest and edit the language used in the question. We are not interested in code length (this is not a code-golf question), but rather, that the code produces the expected result in the fewest, or least amount of total computational operations. \$\endgroup\$ Oct 8 '18 at 18:35
  • \$\begingroup\$ Ok, so if I understand the challenge, you give me a number N. I need to generate a list of numbers between N and M, where M = reverse(N). Each number in the list cannot have duplicate digits, can only consist of digits in N, and must be in strictly increasing order. Is this correct? \$\endgroup\$ Oct 8 '18 at 18:52
  • \$\begingroup\$ Assuming my above comment is correct: 1. Why is 123456789 -> 13256789 invalid, as the maximum is 987654321, which is bigger than 13256789? 2. You need a list of all possible operations. 3. Use the word digit when referring to the individual parts of a number. \$\endgroup\$ Oct 8 '18 at 18:57
  • \$\begingroup\$ @NathanMerrill Yes. Originally included using only the number 9 within the prerequisite criteria, though that inclusion appears to be challenging in itself to explain how the single number 9 can be employed to derive all list items. You are correct about 123456789 -> 13256789 being invalid. Was attempting to include invalid examples and to indicate that 13256789 should not be the next integer in the list following 123456789; the list should be in order from least to greatest integers. Ok, will use the term digit. \$\endgroup\$ Oct 8 '18 at 18:57
  • \$\begingroup\$ Thinking about this more, there's a really simplified way to describe this: You want the all permutations of the digits of N in strictly increasing order. Permutation \$\endgroup\$ Oct 8 '18 at 19:09
  • \$\begingroup\$ @NathanMerrill Yes, that is one way to put it. From perspective here, we are trying to use a number - the indexes of the initial input as a whole number - to generate all lexicographic permutations by using only math and the initial number (the current number) to do so. No loops, swaps, recursion, etc. Which am able to achieve using the code at the linked question, though the approach used there adds 9 to the initial (current) number. The challenge is to reduce the mathematical operations necessary to achieve the result - is at all possible. \$\endgroup\$ Oct 8 '18 at 19:12
  • \$\begingroup\$ I think describing it that way will make this challenge much clearer. Also, to be a fastest-algorithm, you really need to list all possible operations. \$\endgroup\$ Oct 8 '18 at 19:13
  • \$\begingroup\$ @NathanMerrill "I think describing it that way will make this challenge much clearer." Well, did that exhaustively in the linked question - with links to OEIS and previous inquiries which lead to here PPCG for context - which was closed due to "unclear what you are asking" votes codegolf.stackexchange.com/q/173145/31257, codegolf.meta.stackexchange.com/questions/16959. Posted this version of the question as users appear to not gather the original, more detailed question. Is this question codegolf.meta.stackexchange.com/a/16961/31257 clear to you? \$\endgroup\$ Oct 8 '18 at 19:15
  • \$\begingroup\$ No. That question is much too long. I don't think it is the word "Permutation" killing you there, it's everything else. \$\endgroup\$ Oct 8 '18 at 19:21
  • \$\begingroup\$ @NathanMerrill Well, here we are back to square 1. "too long" is a subjective measurement, though have been advised that users actually do have some means to time the "read" of a question, which will more than likely never do, here. This question is the bare minimum, and yet you suggest including more details. Cannot glean every individual users' idea about what is "too long" or does not include enough details. Perhaps somewhere in the middle that am as yet unable to reach. If a user takes the time to read the original question without protesting the length thereof - the details are there. \$\endgroup\$ Oct 8 '18 at 19:25
  • \$\begingroup\$ @NathanMerrill What edits to the original question or this question do you suggest? \$\endgroup\$ Oct 8 '18 at 19:26
  • \$\begingroup\$ All of the close reasons are subjective: "Unclear" is subjective, "Off-topic" is subjective, etc. I can give a full analysis of the other post, but I'd rather focus on this one. My first suggestion is to get rid of most of the requirements in favor of all permutations of the digits of N in strictly increasing order. The second thing you need to do is define what "operation" means. \$\endgroup\$ Oct 8 '18 at 19:28
  • 1
    \$\begingroup\$ "The requirement is to add, subtract, divide, multiply, or use other mathematical procedure, the number 9 to the current number to generate the next number" is (a) not anywhere that I can see in the text of the requirements; and (b) an non-observable requirement, as described in the link I posted of things to avoid when asking questions. \$\endgroup\$ Oct 11 '18 at 7:16
  • 1
    \$\begingroup\$ A requirement is only observable if you can verify it given a black box implementation, so I don't see how any code snippet can demonstrate that it is observable unless it's a test framework which verifies it by black-box testing. \$\endgroup\$ Oct 11 '18 at 7:30

All numeric substrings

I like numbers. Really, really, like numbers. If you give me a string with numerals in it, I want to get all the numbers out of it that I can.


A string.


Every numeric substring, in any order, but only one of each. Numeric here means anything with Unicode General Category Nd (because I'm no xenophobe).


Any reasonable format. But languages that don't allow for multibyte-character I/O should use some numeric or other representation.

Test cases

(input → one ordering of the correct output)

  • 1212 → [1212, 121, 212, 12, 21, 1, 2]
  • 123٤٥6 ‪→ [1, 2, 3, ٤,‪ ٥, 6, 12, 23, 3٤,‪ ٤٥,‪ ٥6,‪ 123, 23٤,‪ 3٤٥,‪ ٤٥6,‪ 123٤,‪ 23٤٥,‪ 3٤٥6,‪ 123٤٥,‪ 23٤٥6,‪ 123٤٥6]‪
  • 12t45 → [1, 2, 4, 5, 12, 45]
  • abc → []
  • \$\begingroup\$ @JoKing, thanks, done. \$\endgroup\$
    – msh210
    Feb 27 '19 at 5:35
  • \$\begingroup\$ I am not convinced by this challenge. To me, it essentially boils down to filtering a unicode string on a character-by-character level, followed by generating all substrings of non-split substrings of the original string. Is ‪٥6 supposed to have any semantic meaning or are those simply two unicode characters? \$\endgroup\$ Mar 2 '19 at 4:36

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