# Sandbox for Proposed Challenges

This "sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to main. This is useful because writing a clear and fully specified challenge on your first try can be difficult, and there is a much better chance of your challenge being well received if you post it in the sandbox first.

Sandbox FAQ

## Posting

To post to the sandbox, scroll to the bottom of this page and click "Answer This Question". Click "OK" when it asks if you really want to add another answer.

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.

When you think your challenge is ready for the public, go ahead and post it, and replace the post here with a link to the challenge and delete the sandbox post.

## Discussion

The purpose of the sandbox is to give and receive feedback on posts. If you want to, feel free to give feedback to any posts you see here. Important things to comment about can include:

• Parts of the challenge you found unclear
• Comments addressing specific points mentioned in the proposal
• Problems that could make the challenge uninteresting or unfit for the site

You don't need any qualifications to review sandbox posts. The target audience of most of these challenges is code golfers like you, so anything you find unclear will probably be unclear to others.

If you think one of your posts requires more feedback, but it's been ignored, you can ask for feedback in The Nineteenth Byte. It's not only allowed, but highly recommended! Be patient and try not to nag people though, you might have to ask multiple times.

It is recommended to leave your posts in the sandbox for at least several days, and until it receives upvotes and any feedback has been addressed.

## Other

Search the sandbox / Browse your pending proposals

The sandbox works best if you sort posts by active.

To add an inline tag to a proposal, use shortcut link syntax with a prefix: [tag:king-of-the-hill]. To search for posts with a certain tag, include the name in quotes: "king-of-the-hill".

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## I've Got The Key, I've Got The Secret

A cryptography challenge in 2 parts.

## Part 1

Implement a pair of programs in any language (the two programs could be in different languages if you wanted) to encode and decode a string of plaintext.

## Input and Output

The encoder must take the plaintext (and an optional key) and return an encoded string. The decoder must take the cyphertext (and an optional key) and return the plaintext exactly as it was given to the encoder.

## Restrictions

• The encoding and decoding code must be entirely implemented in the language - no libraries or cryptography functions may be used.
• The code (encoder+decoder) cannot be longer than 1024 characters.

## Part 2

Implement programs (multiple programs per answer, one answer per entrant) which crack your opponents encryption algorithms.

The cyphertext.

## Output

The plaintext that generated the ciphertext.

## Scoring

I will upvote all answers to part 1 which have working encryption and have obviously made an attempt at golfing their answer.

In order to be eligible to win, an entrant will have to have taken part in both parts of the question. Overall score will be (length of shortest program that cracks your code-(length of encoder+length of decoder)). Highest score wins and winning entrant's entries will be accepted on both questions.

• The obvious place for this to fall flat on its face is if someone is able to implement AES or something similar within the 1024 character restriction. Jun 13, 2012 at 13:06
• Probably better if the methods of the part one programs are disclosed in non-obfuscated language, though with the short length restriction this may not be necessary. Jun 13, 2012 at 15:23
• Forget AES: RSA is easily doable. That aside, you need to define "crack" in part 2. Jun 13, 2012 at 15:35
• Also, it's not clear whether "optional key" means that it's optional to make the algorithm unkeyed (doesn't make much sense, I admit) or optional to supply it, in which case it uses a default key. Jun 13, 2012 at 15:42
• @PeterTaylor I just put optional in to leave it up to the implementer whether or not they wanted to have the key input or hard-coded (or use no key). I'd have thought everyone would have the key input into their program, but I didn't want anyone to feel forced into it by the spec. Hmm, if RSA is doable within the character restriction I'll end up with a load of unbreakable codes which would make for a pretty crap part 2. By crack I meant cyphertext goes in, some time later plaintext comes out. Would restricting the character count further help, or is this question beyond help? Jun 13, 2012 at 16:05
• On that definition of crack, I can brute force for the length of the decoder plus a few bytes to iterate over all keys of the right length and some heuristics to check plausibility of the plaintext. The brute force cracker might even be shorter than the decoder if the decoder wasn't written in GolfScript... I think this question may be beyond help. Jun 13, 2012 at 16:28
• @PeterTaylor Okay, thanks. I like the 'build your own - knock everyone else's down' aspect of this question though. I'll have to find another area where it could apply. Jun 13, 2012 at 16:34
• @Gareth I too like the competitive nature of this idea. I'm looking forward to a question with this plan in mind! Jun 13, 2012 at 19:31
• I think it would be better to split this into a "cops" post and a "robbers" post. Feb 16, 2017 at 9:46
• @wizzwizz4 Wow, this is another blast from the past. I think this pre-dates the cops-and-robbers tag. I always seem to be ahead of my time. :-) Feb 16, 2017 at 9:49

# Countability of Sets of Finite Sets

The aim of this challenge is to code-golf a program which returns an iterator that will iterate over all possible non-empty finite sets of positive integers.

So if running long enough, this iterator should eventually touch on {1}, {2, 5}, {3, 6, 112} (ie none of these should occur "at infinity")

You may choose the order in which you iterate over these sets, but the order must satisfy the following requirement:

Under a particular ordering, if S is the i'th set to be returned by the iterator, then we shall call i the index of set S.

Let a restriction (k,T) be an assertion about a set S that says S has size k and T is a subset of S.

For a given restriction (k,T) and iterator IT, let the restricted iterator be the iterator which takes sets returned by IT and filters out sets that don't satisfy the assertion, iterating only over the ones that do. In other words, if IT iterates over the sequence of all sets, the restricted iterator iterates over the subsequence satisfying (k,T). Now if S is the n'th set returned by the restricted iterator, then we'll call n the restricted index of S with respect to (k,T)

Your ordering must satisfy the property that for any restriction there exists a polynomial P(x) such that for any set satisfying the restriction (with index i and restricted index n), i < P(n)

Note that the following ordering is not acceptable:

{1} {2} {1, 2} {3} {1, 3} {2, 3} {1, 2, 3} {4} {1, 4} {2, 4}...

This is the sequence that comes from counting 1, 2, 3, 4, 5, 6... and listing the set bits in the binary representation of each number.

This is because the restriction (1, {}) satisfies only the sets {1}, {2}, {3}, {4}... whose index i as a function of their restricted index is i=2^(n-1) which is not bounded by any polynomial

## Sandbox Questions

The reason for the strange requirement at the end is to disqualify any variants on the most natural ordering which simply counts upwards from 1 and enumerates the set bits in each number. In this ordering, the n'th set of length-one occurs at index 2^n which is non-polynomial.

I posted this problem originally, but didn't think of the obvious solution and so I left out the final restriction. I'd like to re-post it with the extra restriction. But first I'd like to know what people think. Is there a better way I can word that restriction or a more natural restriction I could impose instead?

• I don't understand the extra restriction, so I can't suggest a rewording, but I can say that it needs one. (In particular: what is k? And what function does T serve? Is it really a parameter of the property?) Jun 18, 2012 at 8:25
• I don't understand it either. Maybe a sample of an ordering, satisfying the requirement, and another one, violating it, would help. Jun 18, 2012 at 15:31
• I understand the restriction now, although I haven't worked through the full implications. Does allowing T to be non-empty make a significant difference at all? Jun 19, 2012 at 6:52
• I don't know. It may not. I guess the size part is the important part. I was just thinking that the ordering should be such that you run into all kinds of sets frequently. Jun 20, 2012 at 7:17

## The One with Two Parts

The aim of this challenge is to create a pair of functions which scramble and unscramble any given piece of text.

Part 1

In part one you post your scrambling function, along with the length in characters and language of your unscrambling function (but NOT its code). The length of the scrambler does not affect your score so you needn't golf it unless you want to. The two functions may be written in different languages if you wish.

Input/Output

The scrambling function should take one argument only - a string containing the input text - and return a string containing the scrambled text. The unscrambling function should also take only one argument - the scrambled text - and return the original text. The input text will be limited to characters in the ASCII set range from 0 to 127.

Part 2

In part two you try to beat your opponents' scores for their unscrambling functions. You MUST use the language they specify for their unscrambler in part one. Please give just one answer to this question containing all your unscrambling functions making it clear which question in part one each function unscrambles (maybe each answer in part one should give its scrambler a name for identification?).

Once the closing date (TBA) has passed all participants should post their unscrambling functions in their answer to part one to prove the length, language and functionality of their function.

Scoring The participants score will be calculated as follows: (unscrambler length from part one) - (shortest unscrambler length from part two). The participant with the lowest score wins and will have their answers accepted on both parts of the challenge. To be eligible to win a participant must have taken part in both parts of the question.

Example

In part 1:

• Bob posts a Python answer and says his unscrambler is a 165 character Python function.
• Fred posts a GolfScript answer and says his unscrambler is a 59 character GolfScript function.
• Joe posts a JavaScript answer and says his unscrambler is a 180 character PHP function.
• Jim posts a Ruby answer and says his unscrambler is 163 character Ruby function.

In part 2:

• Bob posts an 82 character GolfScript function to unscramble Fred's scrambled text. He also posts a 175 character PHP function to unscramble Joe's scrambled text.
• Fred posts a 181 character PHP function to unscramble Joe's scrambled text.
• Joe posts a 150 character Python function to unscramble Bob's scrambled text.
• Jim posts a 156 character Python function to unscramble Bob's scrambled text. He also posts a 91 character GolfScript function to unscramble Fred's scrambled text.

The scores:

• Bob scores 165 - 150 = 15
• Fred scores 59 - 82 = -23
• Joe scores 180 - 175 = 5
• Jim scores 163 - 0 = 163

so Fred wins.

Miscellaneous

I suggest that the closing date be two weeks after the challenge begins, and that unscramblers be posted to part one within 48 hours of closing date in order to be eligible.

• Are there any rules regarding scrambling? i.e. is "Stockholm"->"Stockhoml" a valid scramble? (it may not matter, but I'm curious. And to be clear, the scoring is the difference between your opponent's unscrambler length and your own for the same language? Jul 16, 2012 at 16:39
• @Gaffi No, you scramble however you want. If you want to just output the text as given that's ok, but you probably won't win with that strategy. The aim is to do it in a way that is easy for you to unscramble but difficult for all the others. That way your score will be smaller. Yes, the score is the difference between your score and the score of the best of your opponents' attempts. I'll add an example to make that bit clearer I think. Jul 16, 2012 at 21:27
• I think this gives an advantage to people who use (relatively) obscure languages. If the scrambler is written in J and the descrambler in GolfScript then only people who know both can realistically attempt a descrambler. (NB the rules don't say how the score works if no-one attempts a particular unscrambler). Jul 17, 2012 at 6:59
• I did consider saying that programs that had no attempts at beating them were not eligible to win, but then I thought that if they were scored as though the shortest attempt to beat them was 0 then they wouldn't have much of an advantage. I'll add that into the example scoring. What do you think? I want to encourage answers that are clever or well obfuscated rather than written in Malbolge or something like that. Jul 17, 2012 at 7:28
• Does it mean that since no one attempts to solve Jim's Ruby challenge his chances are minimal that he'll win? That would discourage complicated scramblers or difficult languages. Jul 17, 2012 at 17:12
• @Howard As it stands, yes that's how it would work. The alternative, as Peter Taylor points out, is that people using obscure languages have an advantage. I'm not sure how else I might score unscramblers that no-one has attempted to beat. Maybe give them a score of 0? Please, if you or anyone else has any suggestions for making the challenge as inclusive as possible, let me know. Jul 17, 2012 at 17:51

## Compile BF to TM

Your task is to write a compiler accepting a Brainfuck program (previous challenge: Interpret Brainfuck, wikipedia: Brainfuck) as input and outputting a Turing Machine which produces identical output when supplied with the same (correct) input.

You may select the output format from among the various formats accepted by the answers to Turing Machine Simulator.

The following links may also be useful.
An introduction to programming in BF
BF is Turing-complete
Programming a Turing Machine
Programming Praxis: Turing Machine Simulator

Equivalently, you may write a Brainfuck interpreter in TM, or any partial compilation/interpretation which results in a TM program as described above.

If we consider squares of the TM tape to represent bits (blank=0, mark=1) of the BF memory, then eight squares represent a cell. Each BF instruction translates to a minimum of 8 states of the Turing Machine.

'>' "advance" (++ptr) could be implemented by eight states (sixteen transitions):

adv8 _ adv7 R _


where 'link' represents the first state of the following instruction.

'<' "rewind" (--ptr) can be implemented similarly by making leftward movements and rewriting the same symbol just read.

'+' "increment" (++*ptr) can be implemented by a ripple-carry from the Least Significant Bit to the Most Significant Bit, borrowing "rewind" states to back-up to normal position. If the LSB is on the left, it would look something like this:

inc8 _ link N 1
inc8 1 inc7 R _
inc7 _ rew1 N 1
inc7 1 inc6 R _
inc6 _ rew2 N 1
inc6 1 inc5 R _
inc5 _ rew3 N 1
inc5 1 inc4 R _
inc4 _ rew4 N 1
inc4 1 inc3 R _
inc3 _ rew5 N 1
inc3 1 inc2 R _
inc2 _ rew6 N 1
inc2 1 inc1 R _
inc1 _ rew7 N 1
inc1 1 overflow N 1


where overflow is a HALT state.

For I/O, the simplest way I can think is to place all input on the tape after the memory area, and expand the alphabet to include a symbol indicating the dividing line between the memory portion and the input portion of the tape. In fact, by expanding the cell size to nine squares, this symbol can serve as an input pointer, advancing as the input is consumed. (So "advance" and "rewind" now need 9 states each.) And another new symbol is written in front of the current memory cell to serve as the memory pointer. Inputting a byte therefore consists of schleping each bit over the entire space between the two tape positions with something like this:

input _ set-memptr L _
input 1 set-memptr L 1
set-memptr _ find-inptr R *
find-inptr _ find-inptr R _
find-inptr 1 find-inptr R 1
find-inptr $schlep-bit R$
schlep-bit _ schlep-blank L _
schlep-bit 1 schlep-one L 1
schlep-blank $schlep-blank L$
schlep-blank _ schlep-blank L _
schlep-blank 1 schlep-blank L 1
schlep-blank * deposit-blank R *
schlep-one $schlep-one L$
schlep-one _ schlep-one L _
schlep-one 1 schlep-one L 1
schlep-one * deposit-one R *
deposit-blank _ etc R _
deposit-blank 1 etc R _
deposit-one _ etc R 1
deposit-one 1 etc R 1


where "etc" represents going to get the next bit in similar fashion.

To perform a loop (all BF loops are "while" loops, so the exit control is at the beginning and the end has a simple goto back to the beginning), we need first to check is the current cell is zero,

zero8 _ zero7 R _
zero8 1 body R 1
zero7 _ zero6 R _
zero7 1 left1 L 1
zero6 _ zero5 R _
zero6 1 left2 L 1
zero5 _ zero4 R _
zero5 1 left3 L 1
zero4 _ zero3 R _
zero4 1 left4 L 1
zero3 _ zero2 R _
zero3 1 left5 L 1
zero2 _ zero1 R _
zero2 1 left6 L 1
zero1 _ exit-loop R _
zero1 1 left7 L 1
left7 _ left6 L _
left7 1 left6 L 1
left6 _ left5 L _
left6 1 left5 L 1
left5 _ left4 L _
left5 1 left4 L 1
left4 _ left3 L _
left4 1 left3 L 1
left4 _ left3 L _
left4 1 left3 L 1
left3 _ left2 L _
left3 1 left2 L 1
left2 _ left1 L _
left2 1 left1 L 1
left2 _ loop-body L _
left2 1 loop-body L 1
...
loop-body-final _ zero8 N _
loop-body-final 1 zero8 N 1


So assuming the machine starts at tape-location 0, and the input is on the tape starting at 0 and going to the right, the "startup code" for this arrangement would be

startup _ place$L _ startup 1 place$ L 1
place$_ left270000 L$
left270000 _ left269999 L _
...


Jeez! The output is going to be HUGE! It might be better to treat the BF memory as negative-indexed and reverse all the _L_s and _R_s in 'advance', 'rewind', 'increment', and 'decrement'.

Questions:

Bonuses for optimizations? If I can implement this myself and provide a complete example output, The bonus could be "subtract the difference between your program's output for the example input with the example output". So eliminating states would be far more valuable than shrinking the code. One could possibly achieve a negative score!

Edit: Actually I think this is unreasonable unless the Turing Machine is augmented with non-reading (movement-only or epsilon) transitions. Duplicating every letter of the alphabet just to move over one square is just ridiculously painful. That means this challenge won't link-up nicely with the other one. :(

What about, instead of implementing the compiler, just devise a translation scheme (as above) that leads to a smaller output for a trivial sample program (based on calculating, rather than coding)? "Back of the envelope" compiler.

• "How much detail on BF do I need to supply? Can I simply reference the BF question?" A link to almost any site that describes the language will do. Nov 5, 2012 at 16:52
• Winning condition? Nov 6, 2012 at 13:43
• "Longest prefix containing syntactically-correct Malbolge!" :) ... I'd say have none at all. Perhaps the questioner should be required to accept their own example answer? Nov 6, 2012 at 18:08
• @PeterTaylor Apologies for my last comment. I thought we were on my other answer about the [fun] tag. . . . This one would be a golf: shortest code by character count. But I think a clever system of bonuses could make it interesting. Nov 7, 2012 at 10:06
• The "Equivalently, you may write a Brainfuck interpreter in TM" option doesn't play very well with being a code golf - how are you going to count the length of the TM? Nov 7, 2012 at 11:15
• @PeterTaylor Since the TM question specified 5-tuples, I think it's sufficient to count the tuples (== transitions). You can reduce states by increasing the alphabet (or vice versa), but the transitions would remain constant, I think. Nov 8, 2012 at 5:25
• I'd like to adopt (work on and post) this challenge if you don't want to. Would I be able to? If you do not respond to this message within two weeks, by community guidelines, I am allowed to take it over. Aug 18, 2017 at 3:23
• Yes, please. If you can do something with it, strike while the iron is hot. Aug 18, 2017 at 4:19

# Graphical Output -- Esoteric Artifacts -- The Glass Bead Game

## Draw the Cabalistic Tree of Life

Simply described, the Tree of Life is an undirected network of nodes representing the conduit between matter and higher forms of spiritual energy. It has an upper face arranged in a hexagon, and a lower fact built from equilateral triangles adjacent to the lower two edges of the upper face. Don't label the paths, paths may overlap however you wish, may be single (thick) lines, even. Code Golf. Bonus -100 for labels on the Sephiroth (nodes); Bonus -150 for Hebrew labels.

## Draw a Mandala for each Natural Number

Draw a circle with interesting visual patterns using the input N [ 1 .. \inf ) to determine the number of points around the circle to anchor figures whose shape is also modified by the input N. Actually, 12 seems like a good max: they're pretty much a blur after that no matter what.

//lotsoflines n = 1 ..12

(doesn't need to be this elaborate, This is >600 lines of showing-off.).

. . . need good images for these . . .

## Draw the Ptolemeic System of the Universe

All the stuff I could find is animated already. Maybe this one's done-to-death. :(

Update: Found good stuff on Alchemy. The "Keplar Platonic" model could be fun (3D and all). This one looks good, too. And this.

## Draw the Pythagorean Monochord

aka pre-classical nomogram. I misplaced my Pythagoras books, I know I've got a picture somewhere.

This is the one I was thinking of.

But I think this one's even cooler

## Draw the I-Ching Hexagrams in King Wen Sequence.

I suppose I need to implement this first to avoid copyright issues! :)

• The I-Ching one would have to be in standard order to be remotely interesting, and then becomes as much about kolmogorov-complexity as graphical-output Nov 22, 2012 at 21:24
• For the others: images, please! Nov 22, 2012 at 21:25
• I've emailed the owner of the Alchemy pages asking for permission to use his copyrighted images. Awaiting response. Jan 28, 2013 at 8:25

## Self-Golfing Code?

I don't know if I just didn't search hard enough, but I couldn't find any challenge regarding self-golfing code, or rather, any code that can deterministically reduce another set of text code to a much smaller program, yet still compile/run.

For example, take this:

int main() {
std::cout<<"Hello world 1!"<<std::endl;
std::cout<<"Hello world 2!"<<std::endl;
std::cout<<"Hello world 3!"<<std::endl;
std::cout<<"Hello world 4!"<<std::endl;
std::cout<<"Hello world 5!"<<std::endl;
}


And output this (as one possible solution):

#define A std::cout<<"Hello world
#define B !"<<std::endl;
#define C B A
int main() {
A 1 C 2 C 3 C 4 C 5 B
}


Alternative:

Sub MySub()
Dim aNumber As Integer
Dim someString As String
aNumber = 123
someString = "abc"
MsgBox aNumber
MsgBox someString
End Sub


into (again, as one possible solution)

Sub m()
Dim a As Integer
Dim s As String
a = 123
s = "abc"
MsgBox a
MsgBox s
End Sub


Do we have a challenge for this?

If not, here are some rules I envision:

• Golfing code need not be in the same language as code to be golfed.
• Since compilers/running of code varies, newly golfed code must still run under same environment.
• Possible challenge scoring (multiple options -- thinking code golf):
• 1: Shortest golfing code wins (not my favorite, since you can minimally shorten the base code, yet still write the shortest program).
• 2: Shortest output of a set of pre-defined code (potentially limiting if participants are unfamiliar with the options available)
• 3: Combination of length of golfing code and the output result of the same as input. (Ratio, summation, etc.) -- This I think is my preferred option.
• 4: Multi-player Ratio of golfed size of other participants' own code versus their original submission. (Similar limitations to that of point #2.)
• Sounds more like an auto-golfer than obfuscation. Seems like it would be very hard to make it a fair contest unless you pick a language to golf, and even then it had better be a simple language (no platform dependency issues or compiler options). Feb 13, 2013 at 15:15
• @PeterTaylor My examples are golfing, but either would work. Perhaps golfing would be simpler, then? I agree that the options for usable languages makes this a bit messy... Would one challenge per language be acceptable? (i.e. aligned with most challenges that are language-agnostic) Feb 13, 2013 at 17:36
• Language-agnostic to mean means that you can write a program to do it in any language. Since the language to be golfed can be different from the submitted program, I don't see any incompatibility between making the problem "Write a program to golf Piet" and being language-agnostic. Feb 15, 2013 at 0:18
• @PeterTaylor So then you see no problem with one question per language on which to operate? Are there any proposed scoring algorithms you particularly like/dislike? Feb 15, 2013 at 12:02
• That depends on what you mean. If you're planning to post 10 questions at once, yes, that would be a problem. But I don't see a problem with posting a well-defined "Auto-golf Piet" and following it up two months later with "Auto-golf Perl 5". Feb 16, 2013 at 10:19
• Scoring is an issue. The halting problem means that it's impossible to write an optimal solution, so the scoring must take into account how good the solution is. I think option 3 is the best, and you'll want a big test set (maybe a few kB taken from a real-world open source project) with coverage of the language features. Feb 16, 2013 at 10:22
• Btw, your first example doesn't work. You can't have unmatched quotes in preprocessor directives. Don't know why. Jan 13, 2018 at 18:03
• I honestly think this would be fine if you did something like solely maco-golfing, making it somewhat language agnostic because of gcc -E. Nov 10, 2018 at 14:36

## DeCSS

It is known that the DVD Content Scrambling System can be deciphered with a rather short program (434 bytes of C, 472 bytes of Perl). Can you do better?

<< Test cases go here >>

I don't plan to include a more detailed spec, because it will just wind up duplicating some of the code. The test cases would be in the form of (key, link to data file, md5sum of the deciphered stream).

• And the winning criterion is who is the first to get post from the courts? Oct 3, 2015 at 20:18
• @celtschk, I think that would be unfair. Winning criteria shouldn't really depend on where people live... Oct 10, 2015 at 20:56
• I think you should at least explain the general concept of the spec. Aug 2, 2016 at 22:53
• This actually sounds interesting. @PeterTaylor Perhaps you could use (and link to) Charles Hannum's explanation of the algorithm and post this. (It would be fun to have it as a popularity contest for a program that looks like it's nothing DeCSS related, or a program that furthers the gallery's point about the text vs source code arbitrary distinction - but I don't know if popularity contests are popular any more!) Jun 25, 2018 at 8:25

## Write a compiler/interpreter for ...

Inspired by the lisp challenge here.
It is a series of puzzles.

I don't like to see a simple eval solution, so:

• interpreting the language is fine
• translating the language to a different language is fine.

I think this is specific for each language.

Only the syntax and the basic commands.
Also specific.

Winning criteria should not be code golf.
The goal should be that you can "learn" an other language by looking at the code.

Languages that might be good candidates:

• Lisp
• APL
• J
• Brainfuck (already posted)
• Whitespace
• Forth
• This only works for languages which are small and well defined. BF fits those criteria. Whitespace does too. The others may not. Lisp and Forth have so many dialects that you would have to specify exactly which dialect to support; Lisp, Forth, APL and J might have too many built-ins to fit in an answer: there are character limits. May 12, 2013 at 15:16
• You don't have to provide all the built-ins, but that is why it is here. May 12, 2013 at 15:38
• What defines the "basic commands"? Aug 31, 2015 at 17:54
• I don't know? Maybe that you can do the basic stuff with it like +,-,print,... Aug 31, 2015 at 18:22
• I suggest a programmer can implement the tiniest subset of those languages in order to be Turing-complete, as these are non-trivial subsets that can theoretically simulate the rest of the language...
– user85052
Jun 28, 2019 at 4:17
• Which human is learning the programming language by looking at the code? Aug 26, 2019 at 3:23

# Missile Command

I'm making this CW, because it needs lots of help. I've been toying with this idea for a while. Think "battleship" to get in the right mind-frame. But, instead of ships, what you lay down are tiles which represent a Befunge-style program. This program controls the behavior of guided missiles ejected from the spawn tile. The goal is to program a missile which will obliterate an opponent's program block, as well as guard its own control block.

Haven't nailed-down the board size. 20x20 seems a little cramped.

         1         2
12345678901234567890
____________________1  4x20 program block
____________________2
____________________3
_______@____________4
....................5  12x20 arena
....................6
....................7
....................8
....................9
....................01
....................1
....................2
....................3
....................4
....................5
....................6
___________@________7  4x20 program block
____________________8
____________________9
____________________02


## Tiles

@ spawn

Program control.

I'm imagining these to change direction of the code for "boustrophedon" writing.

this,then\
txen,siht


haven't thought it all though, yet.

/

\

Movement.

F forward move forward one square

B back move back one square

L left turn left 90°

R right turn right 90°

So the submissions would be 4x20 code blocks which compete in a king-of-the-hill style.

• If this is deterministic, won't it be "Last person to submit their program wins"? Jun 7, 2013 at 8:39
• That is a danger, yes. I'm hoping ways around it can be found. There could be a random operator. And proximity detection, or something. Jun 7, 2013 at 8:46

## Find all of the Scrabble numbers:

A scrabble number is a number n whose scrabble representation can score n points. As an example consider 12: its English spelling twelve has value 12 when it is placed on a stretch of six blank tiles. Since the highest ever reported 1 word scrabble score barely exceeds 2000 points, that will be the upperbound for this challenge.

Score and quantities for English:

2 blanks |  x1  |  x2  |  x3  |  x4  |  x6  |  x8  |  x9  |  x12 |
1    |      |      |      | LSU  | NRT  | O    | AI   | E    |
2    |      |      | G    | D    |      |      |      |      |
3    |      | BCMP |      |      |      |      |      |      |
4    |      | FHVWY|      |      |      |      |      |      |
5    | K    |      |      |      |      |      |      |      |
8    | JX   |      |      |      |      |      |      |      |
10    | QZ   |      |      |      |      |      |      |      |


Considerations for either bonus points to scoring or extra requirements:

• Respect the board, only using gaps between double/triple letter and double/triple word scores that occur on a standard scrabble board.
• Respect the tile count for each letter.
• There are non-English versions of scrabble, maybe it should be 'language-agnostic' (lol, but seriously is there a reason to accept only English submissions?).
• Should the 2 blanks be allowed?
• What about tiles which were already on the board and so wouldn't score anything? As for language: one approach would be to make it take the names of the tiles (and perhaps the values and counts of the letters) as input; this would also prevent the problem from being effectively one of Kolmogorov complexity. Jun 19, 2013 at 22:50
• I don't believe that tiles on the board already would pose an issue. If you assume that the board may be prepared with any subset of the tiles beforehand (some may be impossible, but checking that is out of scope) all that is relevant to the problem is which are placed to complete the word. All the tiles points are counted, even the earlier placed, but only the new 7 (or less) tiles may qualify for triple/double-word/letter scores. w.r.t. kolmogorov, If I wanted to make it programming challenge instead of codegolf (so that isn't an issue) then there needs to be a scoring system right?
– Kaya
Jun 19, 2013 at 23:33
• Yes, if it isn't codegolf then it needs a scoring system. I'm not sure what you could use as an alternative scoring criterion, though: it's simple enough logic that pretty much any implementation would be IO-bound, so speed doesn't work; and big-O based tends to be less straightforward than you might think. Jun 21, 2013 at 11:05

# Sort all lines according to their corresponding Levenshtein Distance to the first line.

Shamelessly borrowed from: http://golf.shinh.org/p.rb?Levenshtein+Distance+Sort+FIXED

For a definition of the Levenshtein Distance, look here: http://en.wikipedia.org/wiki/Levenshtein_algorithm

Rules:

Takes input from stdin. Must work for all possible input. Get points for:

Smallest character count. Using Languages that are difficult to golf in. I think character count / the average values from here (http://golf.shinh.org/lranking.rb) might suffice?

• There are a number of ambiguities in the problem description. What is the correct behaviour if the input is empty? In the general case, should the first line be included in the lines which are sorted and output? Should the sort be by ascending or descending edit distance? How should ties be broken? Jun 25, 2013 at 20:23
• As for handicapping: are you going to prohibit built-in or library-provided edit distance functions? If not then the averages you link are not especially relevant: PHP handily wins the existing edit distance question by virtue of its built-in function. Jun 25, 2013 at 20:27
• (That existing question does also raise the possibility of yours being closed for not being sufficiently different). Jun 25, 2013 at 20:28

# Quine with syntax highlighting

I don't really have much of an idea how to properly pose a quine challenge, or what the common syntax highlighting rules are (or aren't) for various languages. So, I figured I'd just toss this concept up here for consideration and let the community flesh it out if they think it's a good idea.

• I'm pretty sure some languages don't even have syntax to highlight Dec 13, 2013 at 20:12
• @JanDvorak Perhaps this would not quite be an "all languages" challenge, then - only languages which naturally lend themselves to syntax highlighting would be eligible.
– Iszi
Dec 13, 2013 at 20:19
• You also can't use a language that cannot render any decent GUI. Also, specifying the amount of syntax highlighting the program needs to generate will be hell. Dec 13, 2013 at 20:36
• I don't think this question is feasible, due to the output restrictions and due to the difficulty in defining the minimum required syntax highlighting. Dec 13, 2013 at 21:09
• I like this idea. I think you could specify an adequate level of highlighting with just keywords, strings or characters and numeric literals each having their own color. Feb 28, 2018 at 21:13
• How would the syntax highlighting apply to the output? Oct 26, 2021 at 18:39

# McDonald's Drive-Thru

Changes from original:

• Provided some clarification of requirements with regards to impossible ordering quantities.
• Added specification to include total cost of order.
• Added specification to prefer lowest cost in case of a tie for number of packages.

TODO:

• Verify package sizes and pricing to be used for this challenge.
• Add pricing to output samples.
• Edit or remove "not have any limitations" rule. As currently written, it may force otherwise unnecessary bloating of code in some languages. (e.g.: PowerShell can handle numbers as uint64 to work with extremely large quantities, but it defaults to int32.)

We want to write a program to help McDonald's Drive-Thru employees assist their customers in ordering Chicken McNuggets. Chicken McNuggets only come in packs of 4, 6, 9, or 20. However, customers may not always be considering this when they pull up to the speaker.

For example, a customer might want to order 50 McNuggets but they really don't care what sort of packaging they come in - they just want to make sure they get 50 McNuggets one way or another. We want to help the customers get the best value out of their order - that is, to compose an order large enough to accommodate their needs in as few packages as possible with little to no excess.

Users will provide a request for n Chicken McNuggets. Your program's task is to provide the user with the sizes and numbers of McNugget packages needed to fulfill the order exactly. If the exact order cannot be fulfilled, the system must output an order which would meet the customer's needs with as little excess as possible. The system must also provide the total cost of the order.

## Rules

• For values of n which can be ordered exactly, output how many of each pack must be ordered to achieve the requested quantity.
• For impossible orders (1,2,3,5,7,11), print "[requested quantity] is impossible. Have [nearest valid quantity >n]:" followed by the normal output for the nearest possible quantity >n.
• Impossible orders cannot be hard-coded. The program must be able to determine whether fulfilling an order exactly is possible without being explicitly told that 1,2,3,5,7, and 11 are impossible.
• Output must exclude any package sizes which do not need to be ordered.
• Output must be in descending order of package size.
• Output must include the sum total cost of all the packages. (Tax not included.)
• Further layout and formatting of the output is up to you, so long as it is unambiguous.
• Program must not have any limitations beyond those inherent to the system or programming language.
• If there are multiple ways to assemble the order in the least number of packages, output the method which has the lowest total price.

Examples:

Input: 8
Output:

2x4


Input: 43
Output:

1x20 1x9 1x6 2x4


Input: 11
Output:

11 is impossible. Have 12: 2x6


My main concern is that this problem may be too similar to this thread:

Work out change

Otherwise, are there any changes that should be made to this?

• My recommendation is to minimize the total cost of the order, rather than the number of packages. Based on these prices: fastfoodmenuprices.com/mcdonalds-prices, the costs are $2.99,$3.89, $4.29, and$5.00. This website lists the "9 piece" as "10 piece", I think that might be an error. Dec 14, 2013 at 0:01
• Why the restriction #3? Dec 14, 2013 at 6:12
• I agree that it's too similar to the existing question. In addition, "nearest valid quantity" isn't unique, and you don't give any hint as to how to break ties. Dec 14, 2013 at 10:17
• @PeterTaylor Tiebreaker is specified as ">n", where "n" is the quantity requested by the user - that is, we want to give the user an option that will have at least as many nuggets as they want to order.
– Iszi
Dec 14, 2013 at 23:37
• @JanDvorak Essentially, to up the difficulty a notch. I figure it's a little trickier to catch the invalid quantities in the process of figuring out the answer if you can't write a simple if statement to match against the known quantities.
– Iszi
Dec 14, 2013 at 23:42
• @PhiNotPi Not sure if that's an error on the site, or a regional difference. The information I posted was based on the linked Numberphile video, which was made in the U.K.. It's also possible they may have changed the menu since then. Presuming that larger packages hold better value in terms of cost-per-nugget than smaller ones, the problem as stated should work itself out to the same goal as you've suggested. However, it might help to differentiate the challenge from the suggested duplicate if we add the total price into the expected output.
– Iszi
Dec 14, 2013 at 23:45
• My question is: how are you going to measure that? How large part of this knowledge are we disallowed from encoding? Can we memorize all but one? Can we special-case 1,2,3? Or, is it that anything goes as long as it either can be generalised to other Frobenius problems, or is inclusive, not exclusive? Dec 14, 2013 at 23:47
• @JanDvorak The program should be able to work out for itself whether or not a given quantity is invalid - that's all there is to it. By its nature, I suppose that means solutions would be able to also handle other Frobenius problems. In fact, I was actually considering a separate "return the largest impossible quantity" problem, where users input several integers and the program outputs the largest quantity that cannot be achieved by adding multiples of those integers.
– Iszi
Dec 14, 2013 at 23:53
– Iszi
Dec 15, 2013 at 2:34
• @Iszi Minimizing cost should serve as a tiebreaker for when there are multiple solutions with the minimum packaging. For example, look at N=36. The solution {0*4,0*6,4*9,0*20} works, but {1*4,2*6,0*9,1*20} is cheaper. (I used the costs {{4,2.99},{6,3.89},{9,4.29},{20,5.00}}) Dec 15, 2013 at 3:07
• @PhiNotPi Ah, I think I misunderstood when Peter said there wasn't a specifier for the tiebreaker. For some reason, I was thinking it was not possible for there to be a tie of that sort. Adding the price aspect definitely helps sort that out, then. Thanks.
– Iszi
Dec 15, 2013 at 3:15
• FWIW, it was my misreading. I failed to see the ">n". Dec 21, 2013 at 12:01

# .... . .-.. .-.. --- .-- --- .-. .-.. -..

Another Hello World challenge, this time with Morse code!

Taking no input, your program must output HELLO WORLD in audible Morse code, printing each letter as it is played. For the purpose of this challenge, the following Morse code guidelines will be followed:

Duration of sounds:

• Dits are one time-unit long.
• Dahs are three time-units long.
• The gap between elements within the same character is equal to one dit.
• The gap between characters within the same word is equal to one dah.
• The gap between words is seven time units long.
• The length of "one time unit" is up to the programmer, so long as it is consistent throughout the message.

Letters:

• H: ....
• E: .
• L: .-..
• O: ---
• W: .--
• R: .-.
• D: -..

I'm a little iffy on that last bullet regarding duration. Should I set a hard standard, or a minimum? If so, what to?

• Set a hard minimum for timing. Otherwise, a golfed solution might have 1 unit = 1 millisecond. Dec 16, 2013 at 22:23
• Tasks which take input are normally more interesting. Dec 17, 2013 at 0:09
• I guess that dahs need to be a continuous tone, not just two dits without a gap? Dec 17, 2013 at 6:32
• @JanDvorak Correct.
– Iszi
Dec 17, 2013 at 6:33
• If you don't plan to post this, I would like to modify it and post it. (If you don't reply to this message within two weeks, by community standards, I am allowed to adopt the challenge.) Dec 22, 2017 at 2:41
• @MDXF What do you suggest for modifications?
– Iszi
Jan 2, 2018 at 15:18

## Code Golf: counting all colors in an image

The goal of this Code Golf is to create a program that counts all colors in an image.

### The input

The input will be a path to the image file.

### The output

The output should be a number that indicates how much different colors your program found in the image.

### The scoring

It's also important that your program supports much image formats, so I'll calculate the score based on this formula:

(character_count * 3) / (number_of_supported_image_formats * 2)


### Some other rules

• The lowest score wins
• You're not allowed to execute an external program
• No Internet access
• A color doesn't just count if it's present in the palette, there really should be pixels of that color in the image.
• You should also count pixels with 0% opacity.
• #FFFFFF with 100% opacity is not the same color as #FFFFFF with 50% (of course, this is the same for all other colors).
• In vector image formats, if there's a red square (for example) with 50% opacity that overlaps a blue square, then this should count as two colors: red and blue.
• In vector image formats, in case of a gradient, the number of colors depend on which colors are used in the gradient. For example, if there is a red/yellow gradient, then you should count this as two colors: red and yellow.
• A paletted image format is another image format than the non-paletted variant.
• SVG 1.0 is another image format than SVG 1.1 (also count for other image formats).
• What counts as a colour? Does a colour count as present if it's in the palette, even if there aren't any pixels of that colour? What about if it's present, but at 0% opacity? On the subject of opacity, are #ffffff at 100% opacity and #ffffff at 50% opacity the same colour? What about vector image formats: does a red square at 50% opacity partially overlapping a blue square count as two colours (red and blue) or three (red, magenta in the overlap, and blue)? What about gradients: does the number of colours depend on the size of the gradient-coloured object? Dec 20, 2013 at 15:25
• Also, what counts as an image format? If a program supports paletted PNG but not non-paletted PNG, does that count as 0 formats, 0.5 formats, or 1 format? If a program supports SVG 1.0 and SVG 1.1 does that count as 1 format or 2 formats? Etc. Dec 20, 2013 at 15:27
• @PeterTaylor: Thanks for your comments! I updated my question. Dec 20, 2013 at 19:16
• I'm sorry, but I'm afraid the core of this challenge is to be as bold as possible when counting the amount of file formats my language's standard library can handle. Dec 20, 2013 at 19:33
• @JanDvorak: Of course, you should also look whether it's really worth to handle another image format, after you made sure to handle some other. If your score doesn't get lower, then it's not really worth. Dec 20, 2013 at 19:35

Since this question is closed, I figured I'd post it here so further issues can be hammered out in Meta instead of the main site.

Known Issues:

• Some rules seem a bit unclear to some users.
• Clarification may be needed on what is needed to qualify for the "win percentage" bonus.
• Win percentage bonus may not be enough to be a real incentive. (This may just depend on the language or implementation.)
• Perhaps the win percentage bonus should be eliminated entirely, or maybe it should just be made a mandatory part of the spec.
• It's been suggested to use a simple 1-9 numbering system for the board positions, instead of any sort of X,Y coordinates.
• May want to allow some flexibility on the input format. (i.e.: Input must still specify the sequence of moves thus far, using whatever addressing scheme is specified in the spec, but leave the delimiters - or lack thereof - up to the developer.)
• Exactly what is expected of the program, such as how it can figure out whose turn it is or what the output should be, seems to need some clarification.
• Some test cases should probably be added.
• Clarification may be needed on the matter of what parts of the game we can assume have followed the guide already.
• Some flaws exist in the chart. (Two already mentioned in comments on the original post.) These should be identified and addressed so that proper expectations for those conditions are clearly set.
• Original post said we would not have to account for null input (i.e.: X asking what their first move should be) but this might be a good enhancement to add.

I personally think this is a great challenge. So far, I've had a very hard time finding a lot of room for optimization and got up to probably 400 characters in PowerShell before I gave up (not even half-way through the chart yet) due to some of the above issues. I'd really like to see what some more serious golfers could do with this, once the spec is properly hammered out.

## Overview

This is the XKCD tic-tac-toe cheetsheet:

It's rather big, I know. But it's also your most valuable resource in your challenge.

## The challenge

Create a program (in your language of choice) that uses the Optimal Move Cheatsheet (henceforth OMC) to output the optimal move when given a sequence of moves.

## The input

Your program will be fed a series of moves in the following fashion:

A3 A2 B2 C2 ...


Where the first combination is always X, the second O, and so on. The letter is the Y coordinate (A-C, A at the top) and the number is the X coordinate (1-3, 1 at the left).

You may assume that the given combination is following the OMC's suggestion for each move at least for the player asking for a recommendation. You can also assume that the input will never be null (at least one move has been made). You must:

1. Figure out whether the next move is for X or O (you don't need to output this)
2. Use the OMC to decide the next move
3. Print the next move in the standard format A3

## Optional:

You may also include the player's chance of winning (as a percentage) for 50 character discount on your score.

• I think a 1-9 system would be easier than any XY system, but not by too much. The biggest issue I think is that if you go by the chart (rather than formulating your own algorithm that plays the same way) you have a ton of data to enter (there are several hundred squares in the two charts). Perhaps limit the input to only sequences starting A1 B2 (or 1 5 if you use telephone keypad numbering)? That's the center square in the X chart and the top left square in the O chart. Dec 23, 2013 at 5:14
• @Blckknght Limiting the scope of the challenge makes it less interesting. Part of the challenge (if not the entire challenge) here is to find ways to shortcut the flow while still putting out accurate results. As for the 1-9 system, the simplification may be relatively trivial but it does help clear out some otherwise unneeded bloat since everyone will probably build in some conversion to a 1-9 system anyway to shorten the code. It also enables some other shortcuts where the same move suggestion applies to multiple situations which are mathematically related.
– Iszi
Dec 23, 2013 at 19:47
• My point is that the chart data so dominates the code size that winning answers will pretty much have to ignore the data in the chart and use an AI. So the challenge becomes "write a Tic-Tac-Toe AI that plays exactly like this chart", which seems less interesting to me than "use (part of) this chart to make an AI with trivial code". I already have working code for the problem and bonus in about 200 non-golfed characters of Python, but it will require many 1000s of characters of data, even if I exploit some symmetries. Even if I was willing to type all that data, an AI will beat it, I'm sure. Dec 23, 2013 at 20:55
• @Blckknght I'm pretty sure even a fairly straightforward implementation of the chart can be fit within about 5,000 characters - especially in a proper golfing language. IRRC, I'd finished the X portion of the chart in about 400 characters with PowerShell before I gave up on my first go at it. Even then, there was still plenty of room for optimization, and that's in a language which is far from optimal for golfing. Certainly, it's nice when you can bang out a quick answer in 15 minutes. But not every challenge has to fit in 500 characters or less.
– Iszi
Dec 23, 2013 at 21:12

## Implement addition using only division (code golf)

Thought you could implement division using only addition? Well try it the other way around!

Your job is to make a function or equivalent program that accepts 2 numbers and adds them using only division.

## Rules

• No importing libraries
• You can't use anything dealing with mathematics except / and /=, (and their equivalents)
• No bitwise operations
• No string operations except input, output, return, and string concatenation
• Interesting. You might have to close some loopholes, though, as some people will just create a giant lookup table. Also, some people could use string operations use perform addition. Is it going to be code golf? Dec 24, 2013 at 16:49
• @PhiNotPi I think so, thanks for the tip. Dec 24, 2013 at 18:42
• Does "no string operations" refer to I/O as well? It's hard to do I/O without string operations of any kind Dec 24, 2013 at 19:21
• @JanDvorak I want to allow I/O - how do I rephrase the question as to allow I/O without allowing math by executing strings? Dec 25, 2013 at 16:17
• "division using only division" looks like an error... Dec 28, 2013 at 10:17
• Is this a code golf, code challenge or a popularity contest? Dec 28, 2013 at 10:56
• @PeterTaylor Thanks :) And @ ProgramFOX, it's code golf. Dec 28, 2013 at 14:36
• @Timtech Not the number of divisions required? Dec 28, 2013 at 15:03
• @JohannesKuhn What are you talking about? Dec 28, 2013 at 15:10
• Tried to calculate 0+0 - the only thing I accomplished was a division by zero ;-) Dec 28, 2013 at 16:20
• How do you prevent solutions like Array(a).concat(Array(b)).concat([0,0]).length? Dec 28, 2013 at 19:53
• Is eliminating string concatenation too restrictive? Maybe only allow the built in conversions from strings to numeric types. Jan 14, 2014 at 11:38
• @Tim I guess so, maybe just disallow eval/expr. Jan 14, 2014 at 11:50
• and would mod be allowed? Jan 14, 2014 at 12:07
• @Tim As it currently stands, no. Do you think I should add it? Jan 14, 2014 at 15:22

## Code-Golf: Write a number as an expression that's as short as possible

The goal of this code-golf is to create a program that takes a number as input (using STDIN, command line arguments, or prompting for input), and outputs that number, but written as an expression that's as short as possible. So, 10000 should become 10^4. If there is no way to write an expression that's shorter than the number, then output just the number.

### Other rules

1. No network access.
2. You're not allowed to execute an external program.
3. Only use the operators +, -, *, / and ^ (that's raising power, not XOR).
4. Order of operations must be taken in account. Use parentheses if necessary.
5. This is a code golf, so the code with the smallest amount of characters wins.
6. The input will always be smaller than 2^32.

### Test cases

500000000   -->    5*10^8     or    10^9/2
999999      -->    10^6-1
10          -->    10
4294967295  -->    2^32-1
16384       -->    2^14


## Recognize spoken numbers of .wav file

The goal of this code golf is to create a program or function that recognizes (and outputs) the spoken numbers of a Waveform Audio File (.wav).
The rules are:

1. No network access and you are not allowed to run external programs.
2. The input will be the file path to the WAV file, and the spoken text will only be one of these digits: one, two, three, four or five.
3. The output must be the recognized spoken number of the WAV file.
4. You are not allowed to use third-party libraries.
5. This is a code golf, so the code with the smallest character count wins.
• What do you mean by convert to text? Encode? Recognise spoken text? Jan 21, 2014 at 18:36
• @Howard: Recognize spoken text. I updated my question. Jan 21, 2014 at 18:38
• That makes it a very subjective challenge. It is quite debatable if a wav file contains recognisable text or not. I can't think of a safe way to put restrictions on the input without making it to a fixed-input kind of puzzle. Jan 21, 2014 at 18:41
• @Howard: You mean, for example, ensuring that the input will only be spoken text without background music? Jan 21, 2014 at 18:43
• This needs some explicit restrictions on input. I assume that you're assuming that the text will be English, but even then there is a lot of accent variety. Most speech-to-text programs which U.S. companies release can't handle many (if any) British accents in their first version or two. I think that the only way this can be reasonably objective is either to invert a TTS program (in which case it's boring - no errors to account for) or to specify a training text and a test text, where it gets to hear the training text read n times and then tries to interpret the test text. Jan 21, 2014 at 18:58
• Maybe it is possible if you restrict the challenge to recognise the spoken digits one, two, three and four. Although still difficult to define clearly spoken there may be small enough variation in the input. Jan 21, 2014 at 19:09
• Maybe you can make a youtube video or something similar that contains all the sound that needs to be recognized; the programs just need to cater to those sounds. Jan 21, 2014 at 19:32
• @Howard: That's a good suggestion. I updated my question. Jan 22, 2014 at 14:14
• What's a "third-party library"? Can C# programs use MS libraries, Obj-C programs use Apple libraries, etc? Jan 22, 2014 at 16:36
• @PeterTaylor: Yes, they can. Jan 22, 2014 at 17:29
• Golfing msdn.microsoft.com/en-us/library/… would make for a rather short and boring answer. Jan 26, 2014 at 15:37
• @PeterTaylor, ProgramFOX: It would make sense to forbid any libraries or programs designed for speech recognition, whether third-party or not. You might want to take a look at my earlier speech synthesis challenge for some ideas on how to word such challenges (and in the comments for some issues I should've thought of in advance). Feb 9, 2014 at 10:08

## Print Lorem ipsum

The goal of this code golf is to write a program that prints EXACTLY this text:

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

The rules:

1. No external resources
2. The shortest code in bytes wins.
• Is there any reason to expect the answers to be fundamentally different to those to existing kolmogorov-complexity questions? Jan 26, 2014 at 15:33
• Won't the winner just post something like cout<<"/*text here*/";? This will probably be pretty boring, as the text needs to be hardcoded in.
– user10766
Feb 6, 2014 at 1:29
• @user2509848: No, I'd expect the winner to be something that packs the text in base 29 or 32 into a raw byte string and decodes it in GolfScript or some similar language. Or possibly some PHP code that starts with <?=gzinflate(. Feb 9, 2014 at 10:00
• OK, but you will need to specify that in the rules.
– user10766
Feb 9, 2014 at 15:35

Here's my first proposal. It just occurred to me that it might be a bit difficult testing submissions without a functioning server, but maybe we can manage without? What do you people think?

The web hosting company I use has a jobs page that looks a bit like this:

If you want to work for them, you have to calculate the correct answer and submit it through this form. But you only have a few seconds in which to do this, so you need a script to do it for you. If you submit the correct answer in time, you're then given a hash code and an email address, and are asked to email your source code to this address, using the hash code as the subject line:

Using any language you like, write a script to download and submit this application form with the correct answer and hidden id field, and then email your source code with the hash code provided as the subject line. You can assume that the HTML source of the two pages is as follows:

# 1. http://jobs.example.com/

<!DOCTYPE html>
<html>
<title>Job Application</title>
<body>
<p>Evaluate 943 + 376 - 394 * 573 * 983 , and submit the answer with the following form.</p>
<form method="POST" action="apply.pl">
<input type="text" name="answer" value="" />
<input type="hidden" name="id" value="5d41402abc4b2a76b9719d911017c592" />
<input type="submit" name="submit" value="submit" />
</form>
</body>
</html>


# 2. http://jobs.example.com/apply.pl

<!DOCTYPE html>
<html>
<title>Job Application</title>
<body>
<p>Well done, that was the correct answer. Now email your source
code to jobs@example.com with the following text in the Subject
<p><code>1a79a4d60de6718e8e5b326e338ae533</code></p>
<p>But hurry, you only have five seconds!</p>
</body>
</html>


The only variable parts of these pages are:

1. The sum (up to 6 numbers separated by any combination of +, - and * with spaces on both sides)
2. The hidden id field that must be submitted with the form.
3. The hash code on the second page

You may assume that the sum can be calculated without overflow using 32-bit integer arithmetic.

• What's the difficulty with having a functioning server? Jan 28, 2014 at 15:53
• @PeterTaylor It won't be possible to actually test anyone's script without a server that can process these applications. This probably isn't a problem for sensible languages, but if someone submitted an answer written in Golfscript or Whitespace then I'd have no idea if it would actually work or not. Jan 28, 2014 at 16:07
• It won't be possible to test them anyway if you send the e-mail to jobs@example.com. I note that you haven't specified that you're after a program: I would specify that answers should be a full program which takes HTTP URL and e-mail address as command-line arguments or as separate lines on stdin; then each person can test with an e-mail address they control. If you're willing to change the URLs a bit then I can host a couple of PHP pages somewhere under cheddarmonk.org. Jan 28, 2014 at 16:34
• @PeterTaylor Ah, of course! It didn't occur to me that the email address could be separated out as input data. We'd have to change the background story a bit though. Emailing a job application to yourself seems a bit daft. Jan 28, 2014 at 16:52
• I don't see why. If you're allowing people advance knowledge of the full HTML structure, you can assume that they have advance knowledge of the target e-mail, and then it's just a case of promoting testable code. Jan 28, 2014 at 17:15

The Poet's Quine:

Write a quine with 1 or more rhyme scheme from http://en.wikipedia.org/wiki/Rhyme_scheme when read. The non-alphanumeric symbols aren't used for rhyming in this scheme (apart from the basic arithmetic signs like plus, minus, times and divided by), neither are comments. Words may be pronounced in any dialect, but it needs to be consistent within the same stanza (no having the first word be pronounced in a Scottish way and the second in a Welsh way).

Contest type would be popularity contest.

Thoughts on this proposal?

• I'm not sure I understand the last two points. Examples? Feb 19, 2014 at 14:50
• "words are pronounced without a heavy accent or dialect" seems to me to be incompatible with "worked and borked rhyme". Feb 19, 2014 at 17:32
• That was more intended to be an example of a rhyme in general, rather than a "no heavy accent" example. I'm not a native speaker, so my pronunciation might not be totally accurate. I'll drop that rule (also could make for more interesting interpretations). Feb 20, 2014 at 14:53
• It seems the scoring scheme actively encourages bad poetry. Maintaining a consistent rhyme scheme throughout is more difficult and better poetically, yet you penalize adjacent repetition of a scheme and give bonuses to unique schemes. Using syllables instead of feet is odd, too. A line of 12 syllables and a line of 8 can work perfectly together if one is anapests and the other iambs. I realize this is a programming site, but if you're going to call it "The Poet's Quine", let's have some real poetry!! Feb 21, 2014 at 23:05
• I'm not really someone who knows a lot about poetry, but those suggestions seem good. I didn't want to make it too complicated though. you say yourself that this site is for programmers, and I doubt there are many programmers out there that know the different di-, tri- and tetrasyllable feet. maybe having a properly feeted poem can be a bonus objective? Feb 22, 2014 at 20:21
• The biggest challenge will be finding a proper scoring system which makes sense both poetically and programmatically. It's definitely possible, but it won't be easy. Poetry is such a wide art and relies just as much on format as on content. And I don't want to force a specific kind of meter on the participants, because that's part of the challenge. Feb 22, 2014 at 20:35
• We could also make it a popularity contest, since poetry is not about the format and content, but about evoking emotions and feelings. A popularity contest might be suited more for such a puzzle. Feb 22, 2014 at 20:37
• Yeah, I think popularity contest solves a lot of the issues here. Of course, it also creates issues of its own, like the inexplicable number of "To be or not to be" entries on the aphorism challenge. But...lesser of two evils. :) Feb 28, 2014 at 19:32
• What issues are you thinking about? maybe some extra rules can make this work. Mar 4, 2014 at 8:09

# The shortest C program which generates the most instructions

Write a very short C program (length being defined by character count) which generates the most instructions when compiled. Of course, indicate your compiler, the version, and your operating system, and say what your program does. Linked libraries do not count!

### Score

• Base score: 1/(characters) * (instructions)
• Bonus: if it computes something "useful," +20%

I'm fascinated by C challenges and compiler oddities, but I'm not sure about this question because of the variance you'll get between different compiler versions. Would it be acceptable to ask users to use an online resource which will compile C to assembly? I found two after a cursory search:

• With the chars/instructions formula, the score can approach 0 (e.g. use C macros that, when nested N times, generate 2^N instructions). Also, make it clear that linked libraries don't count. Feb 25, 2014 at 14:57
• @ugoren I'm confused about what you mean by chars/instructions, maybe I should have written instructions/characters instead of 1/characters * instructions? Noted about the linked libraries. Feb 25, 2014 at 15:03
• define DUP(x) x x and DUP(DUP(DUP(DUP(DUP(DUP(x++;)))))) - this duplicates x++ 64 times. Add another DUP and you get 128 times. Feb 25, 2014 at 15:20
• I caught my mistake. The score can approach infinity, not zero. Still, I think, a problem. Feb 25, 2014 at 15:22
• @ugoren Probably too many straightforward abuses to bar them all, eh? Feb 25, 2014 at 15:29

# How many pizzas do I need

Write a program that figures out the minimum number of pizzas I need to order and the amount of left overs I will have.

### Requirements

• Each pizza is 8 slices
• Each person gets one choice of pizza topping, represented by a letter A-Z
• Input in the format PVBC 2. Where each letter represents the choice of 1 person (e.g. P=Plain, V=Vegie, etc...), and the number is the amount of slices each person is allowed to eat. Letters can be in any order and do not need to be grouped.
• If I don't need a full pizza I must be able to do half one topping and half another topping, the output for a half and half pizza will be denoted by X/Y where X and Y are different toppings
• If I need multiple of a certain type of pizza they must be shown on one line (e.g. 2 x V Pizza). If there are different combinations the both result in the same, least, amount of pizzas, either output works
• Output must match the format below of one type of pizza per line and a comma separated list of left overs. The output must show the minimum amount of pizzas and leftover possible.

### Extra Credit

• -20 - Take a 3rd argument that allows you to input the number of slices in a pizza, assume it will be an even number such that you can split it in half

Sample Input/Output

PCPVCB 3              (6 slices P, 3 slices V,  6 slices C, 3 slices B)
1 x P Pizza
1 x V/B Pizza
1 x C Pizza
2 slices P, 2 slices C, 1 slice V, 1 slice B left over

VBBCBBB 2             (10 slices B, 2 slices C, 2 slices V)
1 x C/V Pizza
2 x B Pizza
6 slices B, 2 slices C, 2 slices V left over


The 2nd example has many other combinations that could result in only 3 pizzas, this is just an example of what an output might be.

The shortest code wins.

• I can't say for sure, but I may have seen a similar challenge before. If not, it seems good to me.
– user10766
Feb 18, 2014 at 19:20
• The use of the word "preferences" is confusing to me, because it suggests some kind of optimisation problem where people might get their second preference and you have to optimise for overall satisfaction. In addition, I don't find either the input or the output specification sufficiently clear. For the input, is there any guarantee that the letters are grouped (i.e. that PVP 1 will never be given as input)? And are the 4 letters given the only ones which may be used, or could there potentially be 26 different preferences? How much flexibility is there in the output? Feb 18, 2014 at 21:12
• @Danny, the one problem with this question is that because of my voracious appetite, there would be no left over pizza... ;) Feb 18, 2014 at 21:15
• @PeterTaylor I made edits to hopefully address all of the parts you saw that were possibly confusing. Can you look at the question again and let me know what you think. Feb 19, 2014 at 13:44
• @Danny You might want to add that you want the minimum amount of ordered pizzas/left overs - otherwise there exists a trivial solution where each person gets his own pizza (provided slices<=8). Feb 26, 2014 at 8:19
• Hello! This looks like a good but abandoned meta post, would you be willing to offer it for adoption? (If you want to, you can still post to main.)
– user58826
Jun 9, 2017 at 16:07

# Resurrect Adobe SubScript.

In an obscure conference procedings volume of forgotton lore, there's a quaint little paper which describes an early effort to implement a published subset of Adobe Postscript. There a line in the bibliography! :) But it cannot be found Nobody's ever heard of it. :(

Adobe Systems, "SubScript Specification", 1984.

But there's obvious utility in such a thing. So this is a hypothetical Micro-Manual Postscript, and its name shall be ASS[*]. :)

ASS is a dynamically-typed stack-based programming language with powerful graphics primitives. It has support for floating-point arithmetic, arrays and dictionaries.

The scanner reads white-space delimited tokens and attempts to interpret the token as a decimal floating-point number with optional sign (+/-). The program may (but is not required to) support exponential notation. Failing to recognize a valid number, the token becomes a name object, an atomic symbol type which is identified by the name (an "interned" string).

# Types

As suggested by the scanner behavior and the operator list , there are the following object types:

• floating-point numbers (coerced to integer where appropriate)
• names (usually an index into a string table, for easy comparisons)
• arrays (an indexable sequence of objects)
• dictionaries (a key-value map of objects)
• operators (a pointer to a built-in function)

# Operators

Operators are the basic actions predefined in the dynamic name space.

## Stack Manipulation

• any   pop   -
pop an object from the operand stack

• any1 any2   exch   any2 any1
exchange top two elements

• anyN anyN-1 ... any0 N   index   anyN anyN-1 ... any0 anyN
retrieve object from stack by position

where N is treated as an integer.

## Arrays.

• N   array   array
create a new array of length N

• any0 any1 ... anyN-1 array   astore   array
fill array with objects from stack

• array   aload   any0 any1 ... anyN-1 array
spill contents of array onto stack

• [   any0 any1 ... anyN-1   ]   array
construct an array

• array index any   put   -
put a value into array

• array index   get   any
retrieve value from array

where index is treated as an integer.

The typical way to implement the array syntax is using an auxiliary type, the marktype object, and an operator counttomark. This is an implementation detail and is not strictly required but may be found to be convenient.

• -   [   mark
produce marktype object as a sentinel on the stack

• mark anyN anyN-1 ... any1   counttomark   mark anyN anyN-1 ... any1 N
count objects up to mark

Then the ] operator may be implemented in terms of the other array operators.

• mark anyN anyN-1 ... any1   ]   array
{ counttomark array astore exch pop }

## Dictionaries.

• N   dict   dict
create a new dictionary, an associative container with room for N name-value pairs

• dict   begin   -
push dictionary on dictionary stack, making names part of the dynamic name space

• -   currentdict   dict
push copy of topmost dictionary on dictionary stack to the operand stack

• -   end   -
pop and discard the topmost dictionary on the dictionary stack

• name any   def   -
associate name with any value in topmost dictionary

• name   load   any
lookup name in each dictionary in the dictionary stack from the top-down, returning the first match, or error if not found

## Matrices and transformations.

A matrix is a 6-number array [a b c d e f] which represent a left-multiplying affine transformation matrix with the constant right-most column omitted.

 a b 0
c d 0  =>  [a b c d e f]
e f 1

• -   matrix   matrix
returns a new identity matrix [1 0 0 1 0 0]

• matrix   setmatrix   -
make matrix the current transform in the graphics state

• -   currentmatrix   matrix
return current transform from the graphics state

• x y   transform   x′ y′
transform (x,y) pair by current transformation matrix

Transforming a point involves multiplying the homogeneous vector through the transformation matrix:

          [a b 0]
[x y 1] * [c d 0] => [x' y' 1]
[e f 1]


or, equivalently

x' = a*x + c*y + e
y' = b*x + d*y + f


## Path description.

• -   newpath   -
• x y   moveto   -
• x y   lineto   -
• -   closepath   -

## Clipping.

• -   clip   -
• -   clippath   -

## Painting.

• -   erasepage   -
• -   fill   -
• -   showpage   -

The fill operator is where the magic happens. This operator is responsible for performing all of the graphics algorithms in sequence:

• Shape Mapping
Tranform the coordinates of the path from user space to device space using the current transformation matrix.

• Shape Clipping
Clip the portions of the path that lie outside the clipping path.

• Filling
*Perform a scan-line rasterization of the (may assumed closed-) polygon described by the path into the output frame buffer.

And showpage copies the contents of the framebuffer to the actual output mechanism (window or file as described above).

... need to fill this out a little more. Math, graphics state, errors. Describing stroked lines is too much, I think. I'm not sure if it needs the forall operators for iterating through arrays and dicts. I'd like to avoid any need for overloading different types under the same operator name, and calling back to user code from an operator.

Output may be to a window, or to a file in a simple format, like pgm or even a text-file of hashes and spaces for rough bitmaps. No half-toning. Only bi-level filling of convex polygons will be required. But a program may handle more colors if desired.

This is CW in case anybody wants to help me type-in the basic operators.

# Questions

Does it need anything more? Should something be removed as unnecessary? Does anyone have the spec??

Perusing my ps implementations of the graphics portions linked in the comments, I've noticed the following needed operators:

length
sub
roll
eq
array copy
mul
div
ne


I think it needs loops, too. It's possible to do with just recursion, of course, but loops are nice. And length, I think, needs to be polymorphic, operating on array or dict to retrieve the size for making copies and calculating indices. Add sin and cos, too.

And this would be a .

[*] The moniker "ASS" is not intended as a disparagement of Adobe Systems nor any of their stupendous intellectual property. Rather it is merely intended to express frustration at the encountered difficulty in locating this document.

• So this is intended to be a subset of PostScript: are you going to point people at a PS spec for the nitty-gritty details about things like the precise implementation of path filling? Also, if the idea is to be minimalistic, why have both mark and [? Jan 11, 2014 at 13:19
• I'm hoping I can concisely specify everything so it's self-contained and not need to refer to a PS spec. ... Good point about mark. I suppose I can require [ and ] and suggest mark ... counttomark as a possible way to implement it. Jan 11, 2014 at 13:22
• oh. I see what you mean now. removed mark as a separate entity. It isn't needed. Jan 11, 2014 at 13:32
• My idea is to follow the most basic part of the original Warnock paper which is the basis of the Adobe Image Model. I've got some excerpts here. Jan 11, 2014 at 13:46
• I don't see any way to create a non-identity matrix. Jan 24, 2014 at 9:20
• You can construct any matrix using the array notation. There should also be user space transforms: rotate, scale and translate. They're usually part of the graphics state, so I didn't put them under matrices. Jan 24, 2014 at 9:25
• This spec from the 80s would be gold for implementing postscript. Offering a glimpse at the intermediate stage between the Warnock/Wyatt paper (which describes the image model in the syntax of the Xerox Mesa language) and the PLRM 1ed. Warnock/Wyatt has been described as "smuggling" the ideas out of Xerox. ... Ugh. I forgot to add some control structures. Mar 1, 2014 at 10:22
• I've got implementations of paths, matrices, clipping, and filling in postscript. Perhaps I should wrap these up and just require the data structures and scanning to load and use them. Mar 1, 2014 at 11:33
• Hello! This looks like a good but abandoned meta post, would you be willing to offer it for adoption? (If you want to, you can still post to main.)
– user58826
Jun 9, 2017 at 16:08
• Thanks! ... Done. Jun 11, 2017 at 10:00

## Off-topic bullshit detector

You run a blog about astronomy and for each post there is an area for comments, where people post comments. So, when you post news about the discovery of a new exoplanet, quickly there are some people commenting about its habitability or about the methods using for their detection, and you do answer those comments, very nice.

You already have a very good spam detector that handles people who tries to post links to viagra-selling sites, so you do not worry with these.

But there is always people who you really hate and makes you very tired. People who insists to post comments that every astronomer is tired and angry to see:

• Comments about religion arguing that instead of looking to the sky, people should look for God.
• Comments claiming that this is all a big lie made up by governments around the world, and in fact the man never went to the Moon and the Earth is flat.
• Comments about planet Nibiru, planet Hercolobus, planet X, planet Nemesis and similars.
• Comments about Mayan, Sumerian, or Nostradamus profecies about the end of the world in any particular date.
• Comments about the CIA hiding ETs in Area 51 captured from Roswell and similar stuff.
• Comments about conspiracies by secret groups controlling or willing to control the world, like the Illuminati, the Masonry, the New World Order, and similars.
• Useless flamewar comments that happens when people from two different groups in the previous categories disagree one with the other, posting comments that makes you sometimes doubt that intelligent life exists on Earth.

Your task is: Create a complete program that receives as input a text comment limited to 300 characters and outputs Yes/No, 0/1, Approve/Reject or something similar, rejecting the bullshit comments and accepting the valid ones.

Further, we have a few restrictions:

• As a policy of your company, everyone may comment any post at will, without the need of prior registration, so you can't build some sort of reputation barrier system for this.
• You can't also make comments be approved by other frequent commenters based in some reputation system. This happens because your competitor did that and the result was that the people that you want to avoid managed to take over the site being the ones with the most reputation and thus completely ruining your competitor's site. So, your boss decided that you should not build a reputation system.
• No use of external resources in the internet.
• You are allowed to save files in the disk or to use a database (please do not abuse this rule).
• If you do need, you can add a training program to pre-populate the program data.
• Your algorithm must be deterministic and consistent. I.E, in a given state for a given input, it always produce the same output. So, do not make it randomized nor use as input something like the colors of the pixels in the screen, the system clock or similar sources of entropy.
• [Lacking a rule to avoid exploiting the score system by overfitting the test data].

This is still lack a winning criteria. Don't know if should be , some sort of or something else. is surely out-of-question for this. What do you think?

Further, to make it testable, this will need some sort of corpus which falls in those bullshit categories and some perfectly valid as well. If you do have some suggestion on this, please, drop a comment.

• I could say that people who post anti-creationist comments are just as annoying...
– user10766
Mar 3, 2014 at 3:35
• Are comments about creationism OK when they are replying to comments about extraterrestrial life? Mar 3, 2014 at 7:23
• Why no database access? Having to reimplement a database makes this challenge harder, but not more interesting. Speaking of which, code-golf requires hard criteria for accuracy (and absolute accuracy is impossible to achieve here). The usual solution is to use the popularity metric while telling people to strive for accuracy / accuracy and consciseness / accuracy and opacity / ... Mar 3, 2014 at 7:26
• What makes you think the Illuminati won't use their moon-based supercomputer to figure out how to get around your filter? Mar 3, 2014 at 15:21
• @Geobits That is easy: The man never went to the Moon, so couldn't the Illuminati do it either. In fact, it is impossible to go to the Moon because God made the Earth flat and you can imply by the Genesis that ETs do not exists. Mar 3, 2014 at 15:28
• @JanDvorak. Ok, relaxed the databases requeriment. Mar 3, 2014 at 15:31
• @user2509848 Ok, added this: "Useless flamewar comments that happens when people from two different groups in the previous categories disagree one with the other, posting comments that makes you sometimes doubt that intelligent life exists on Earth." Mar 3, 2014 at 15:32
• What? No, Genesis clearly states that aliens are among us. How do you think the Illuminati got started in the first place? I'm pretty sure the "boss" in this scenario is a member anyway. He's clearly going to use your program to figure out the limits of automated bullshit detection. On topic, I like the spirit of this question, and I'd label it a code-challenge. Mar 3, 2014 at 15:36
• @Geobits, yes I think to that it should be a code-challenge, but don't know yet how to score that. If I don't figure out a good scoring system, will default to popularity-contest. Mar 3, 2014 at 15:41
• If you had a corpus, a basic points system seems easiest. +x for each correct reject, -y for each incorrect, something like that. If entries tie on base score, default to either code length of popularity. Mar 3, 2014 at 15:45
• This is an interesting idea, but it does seem tough to come up with objective scoring unless there are known inputs (i.e. not "Comments about..." but "These 3 sample strings that comment about..."). But then people will just optimize to those inputs, so you'll probably get better & more interesting results if you go the popularity route and leave the detection categories open-ended as they are. Mar 3, 2014 at 15:46
• +1ed Geobits for simultaneously having the same idea I did. Testing corpus is the way to go if you want it objective. Mar 3, 2014 at 15:47
• OK, seems better.
– user10766
Mar 3, 2014 at 16:16
• Basically you're asking for a Bayesian spam filter. The tricky thing is to write a spec for a Bayesian filter which isn't so restrictive that there's no freedom to be creative, isn't so loose that people can cheat, and doesn't require you to keep the test data secret. Mar 3, 2014 at 16:17
• @PeterTaylor Yes, the solution would probably be a Bayesian spam filter, but it does not needs to be. Yes, that spec is somewhat tricky to fine tune. Further, I still need a corpus. Mar 3, 2014 at 16:52

Repost from previous sandbox, I realize this is somewhat similar to the Limerick program abit higher, but this was made before that.

The Poet's Quine:

Write a quine with 1 or more rhyme scheme from http://en.wikipedia.org/wiki/Rhyme_scheme when read. The non-alphanumeric symbols aren't used for rhyming in this scheme (apart from the basic arithmetic signs like plus, minus, times and divided by), neither are comments. Words may be pronounced in any dialect, but it needs to be consistent within the same stanza (no having the first word be pronounced in a Scottish way and the second in a Welsh way).

Contest type would be popularity contest.

Thoughts on this proposal?

• Do you guys think this is ready for posting? Mar 5, 2014 at 14:12

Weighted letters combination to get 2014.

If a=1, b=2, c=3, d=4,...z=26, which letter combinations (in particular order) when operated by any one or two or three or all four of +,-,X,/ (in any order) will give 2014 as the result?

For example, j*t*j+n=10*20*10+14=2014, t*j*j+n=20*10*10+14=2014 and n+j*t*n=14+10*20*10=2014

are three different combinations.

N.B. - max number of consecutive same letters should be 2, see link http://www.oxforddictionaries.com/words/are-there-any-english-words-containing-the-same-letter-three-times-in-a-row

• This needs a lot of work. Firstly, questions which don't take input are almost always improved by generalising them to take a parameter: in this case, 2014 could be the test case rather than a hard-coded constant. You haven't specified what the output should be: do you want a list of all solutions (which could be an insanely large list, even if equivalence classes under permutation of arguments are represented by a single element)? Asking for any solution has a trivial approach of just building a long sum. Mar 9, 2014 at 8:27
• Then there's the issue of your final constraint and link: it appears to have no relevance at all to the question, unless you previously intended to state that the expression should, once all operators are removed, form an English word. In that case, it would be as well to just provide a link to a dictionary file for Windows users. You should also be aware that your question might be closed as a near-duplicate of one of these earlier questions. Mar 9, 2014 at 8:32
• @PeterTaylor, thanx for pointing out the difficulties, I was just playing with this idea, if we choose the word "mathematics", it has 10 places for +,-,* and /, each of the 10 places can have any one of the four operators, that amounts to $4^{10}=1048576$, that's just impractical to find out what just one word "mathematics" adds up to. Mar 10, 2014 at 11:59

Your task, should you choose to accept it, is to convert an image into ASCII art. Essentially, your program has to do precisely what picascii.com does.

Rules:

• You must take the image from stdin or read it from a file specified in the command line.
• You must output to stdout or to a filename specified in the command line.
• Your program must take input in a format that ImageMagick supports. You can choose any format you want, however. If you want to read ppm images and we have to pass a jpeg through ImageMagick first to use your program, that's fine.
• Given the above, your program itself must use only standard libraries, even for loading the image.
• You must only output printable ASCII characters (that's 32-126 plus CR and LF).
• You can choose in which font or setting your image should be viewed in, e.g. it might look good in a terminal but awful in a stackexchange code block, or vice versa, or maybe it only looks good with Courier New size 12, etc.
• The largest edge of your output must be at least 25 characters and at most 200 characters long.
• Aspect ratio must be preserved as much as possible within one fixed-width character size. e.g. if you have a 400x320 pixel image, and the fixed-width font you're outputting for is 8x13 including spacing, your output must be at least 25x12 characters, or it can be 50x25, 125x62, etc., with a maximum size of 200x98.
• Provide at least two sample inputs & outputs with your submission. Outputs can be stackexchange code blocks or links to paste bins or screenshots of the output viewed in the environment you intended it for, etc.
• Your score is the byte count of your source code. Lowest score wins.

However, I want the output to bear some reasonable resemblance to the input. I don't want this to be subjective. I'd rather have a hard limit that people can hack around.

Opening suggestion: maybe something like: given a font size of 8x13, if the image is converted to grayscale and quantized to 8x13 blocks, and your solution is converted to an image, scaled to fit, and also quantized to homogeneous 8x13 blocks where the value of each block is the percentage of filled-in pixels for each block, the average distance between the image blocks and your output blocks must be less than X.

• You should delete it from the main site for now because you can't really change the rules once somebody posts an answer. You can repost it when you think it is ready.
– user10766
Mar 11, 2014 at 18:53
• @hosch250: Good idea, just deleted it. gotta make it a good one! Mar 11, 2014 at 19:02
• @hosch250: The link isn't broken, it's just a deleted question, and can only be viewed by me and the mods. I wanted to not lose the link but it's there in the edit history I guess. Mar 11, 2014 at 20:26
• It is still in your account page too.
– user10766
Mar 11, 2014 at 21:55
• I think this would be quite dull as a code-golf challenge. The optimal solution is to simply read every other line of a PGM file and convert each number into ASCII 32 (space) or 33 ('!') based on some threshold value. Without a code length restriction, we could add more interesting features like Floyd-Steinberg dithering and matching letter shapes to image features (e.g., using / and \ in places where diagonal likes are detected). Mar 14, 2014 at 0:15
• @squeamishossifrage: Hmm interesting. I was going for making an objective criterion that would make that not the optimal solution, so you'd have to use more than a few characters, but that'd be awkward. Making it a popularity contest would definitely lead to more creative solutions.. I will consider it Mar 14, 2014 at 0:53
• Hello! This looks like a good but abandoned meta post, would you be willing to offer it for adoption? (If you want to, you can still post to main.) Due to community guidelines, if you don't respond to this comment in 7 days I have permission to adopt this.
– user58826
Jun 9, 2017 at 16:19

# Tic-tac-toe

Tic-tac-toe is a paper-and-pencil game for two players, played on a 3×3 grid.

## Rules of Tic-tac-toe

• The first player uses X, the second O as a symbol.
• Tic-tac-toe is round-based. So in the first round, X has to place his symbol on any free grid cell, then O has to place his symbol on any free grid cell and so on.
• The game is over when any player manages to get three of his symbols in any row / column or the diagonal. That player has won. So every game has at least 5 turns.
• The game is over when all cells are full. This is a draw. So every game has at most 9 turns.

## Rules of this codegolf

• This is a . So shortest code wins.
• Every code has to be playable. This means, at first the user has to be able to decide which player he wants to be (first / second or X / O). The other player will be the computer.
• Optimality: The computer has to use the optimal strategy. This means, the computer can never lose (see Wikipedia).
• Bonus: If you can play it via GUI, you get -200 characters.
• You should provide an ungolfed version

## Background

I've just seen this question on StackOverflow where somebody seems to have hard-coded an optimal player and wants to know how to reduce the size of his program. Lets see how far we can get :-)

## Related questions

• What is the difference between this question and this proposed question? I am not saying that I think that people are wrong in +1ing this and -1ing mine, I just hope to find out how I could have improved it. Mar 27, 2014 at 16:14
• @kitcar2000 it may simply be because yours was posted later. It would have been useful if the downvoter has posted a constructive comment... Apr 16, 2014 at 9:23
• @kitcar2000 I also think that time is important. Why did you add another proposal? Apr 16, 2014 at 9:33
• @moose Sorry, I accidentally undeleted it. Apr 19, 2014 at 14:09