Sandbox for Proposed Challenges

Question

What is the Sandbox?

This "Sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to the main page. 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.

To post to the Sandbox, scroll to the bottom of this page and click "Answer This Question", or click on the "Add Proposal" link below. Click "OK" when it asks if you really want to add another answer. Write your challenge just as you would when actually posting it. 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.

To add an inline tag to a proposal use shortcut link syntax with a prefix: [tag:king-of-the-hill]

See the Sandbox FAQ for more information on how to use the Sandbox.

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• Most people include applicable tags in their proposal, so for instance you can search for all king-of-the-hill proposals by merely adding the tag name in quotes to the search query.

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Answer 1

Prove Your Language's Turing Completeness code-golf

The goal is to show whether your language is or isn't Turing complete with the shortest program possible. This is different than "interpret BF" questions, since that's only one way to show the completeness of a language.

This question will maintain one for each programming language (using a snippet), so the goal is to have either the shortest Turing machine, or the shortest proof that your language isn't Turing complete.

Good luck with Malboge.

This is probably a weak question so far, and so it needs your suggestions!

• Also, I'm not really sure how it'd work for non-Turing complete languages...

Answer 2

Hello, Loophole Abuse!

Assignment

Print the following string:

Hello, World!

Gimmick

you know the meta post "Loopholes that are forbidden by default"? Yeah, those don't apply here. In fact, you're actively encouraged to use as many as possible and combine them in weird ways. the more you use in a way that other users like, the more chance people will vote for you.

In addition, to prevent trivial answers getting all the glory, your program must also work in the event that the characters that make up the source code are reversed (this includes the separate characters of a string). This includes external sources, multi-character compiler and execution flags, file names and anything else that is essential for the execution of the software (like Metagolfscript IDs).

Scoring

This is popularity-contest.

Answer 3

PPCG New Question Generator

code-golf

Specification

Write a program that does the following, given a string s and an integer n (as a file, STDIN, or command line arguments):

1. Determines the n most used characters in that quote. If there are two characters that are equally used, the character with the lower ASCII value takes priority.

2. Returns the text and the character in the following format:

   Return the following text:
   
   >{string}
   
   But there's an ORIGINAL TWIST! You cannot use the characters {characters} in your answer. As this is code-golf, the answer with the least characters wins. Have fun!
   

Specifics:

1. You need to display {string} in blockquotes using Markdown formatting, not HTML. So if the string spans multiple lines, you need to prepend each line with >.

2. You also need to display {characters} using proper grammar and in order from most used to least used. For example, with "a", "b", and "c":

   You cannot use the characters "a", "b", or "c" in your answer.

Example

In this example, n is 4, and s is:

I have loved flowers that fade, 
Within whose magic tents 
Rich hues have marriage made 
With sweet unmemoried scents: 
A honeymoon delight,
A joy of love at sight, 
That ages in an hour
My song be like a flower!

The output is:

Return the following text:

>I have loved flowers that fade, 
>Within whose magic tents 
>Rich hues have marriage made 
>With sweet unmemoried scents: 
>A honeymoon delight,
>A joy of love at sight, 
>That ages in an hour
>My song be like a flower!

But there's an ORIGINAL TWIST! You cannot use the characters "e", "a", "h", or "o" in your answer. As this is code-golf, the answer with the least characters wins. Have fun!

Answer 4

Remove Pieces from Chess Position Notation

You should write a program or function which receives a string representing a chess position as input and outputs or returns the position with only the pawns and kings left.

The positions in the input and output are described by FEN notation:

Each rank is described, starting with rank 8 and ending with rank 1; within each rank, the contents of each square are described from file "a" through file "h". Each piece is identified by a single letter taken from the standard English names (pawn = "P", knight = "N", bishop = "B", rook = "R", queen = "Q" and king = "K").[1] White pieces are designated using upper-case letters ("PNBRQK") while black pieces use lowercase ("pnbrqk"). Empty squares are noted using digits 1 through 8 (the number of empty squares), and "/" separates ranks. (taken from Wikipedia)

For example

rnbqkbnr/pp1ppppp/8/2p5/4P3/2N5/PPPP1PPP/R1BQKBNR

describes the board

---------------
♜♞♝♛♚♝♞♜
♟♟  ♟♟♟♟♟

    ♟
        ♙
    ♘
♙♙♙♙  ♙♙♙
♖  ♗♕♔♗♘♖
---------------

With everything except kings and pawns removed it becomes

---------------
       ♚
♟♟  ♟♟♟♟♟

     ♟
       ♙

♙♙♙♙ ♙♙♙
       ♔
---------------

and expressed with the FEN string

4k3/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/4K3    

Input

• A FEN string consisting of the characters 12345678PNBRQKpnbrqk/.
• The input describes a valid chess game position.

Output

• A FEN string describing the position with knights, bishops, rooks, queens removed.
• Output might not be a valid chess position in some extreme cases.

Examples

TODO

This is code golf so the shortest entry wins.

Answer 5

Pareto optimality challenge

Write a class that maintains a pareto optimal set. This class must have these three methods:

k(int n): Constructs the class. N is the array size that all of the other methods must use.

boolean k.p(int[] n): Adds n if there exists no entry m in k such that each single term of m is greater than each corresponding term in n. The method must also return true if n has been entered into k, or false otherwise. n can be assumed to be of the length specified by the constructor.

boolean k.s(int[] n): Returns true if n was previously entered by the above method and there exists no other term m in k such that each term of m is greater than each corresponding entry in n. Returns false otherwise.

This is code golf, so shortest entry wins. Yes, programming languages without classes may be used, but all the usual properties of classes must be satisfied by the three methods above.

Answer 6

ASCII Snake

NOTES

It was pointed out to me that we already have had at least 2 snake challenges before. However, seeing as they are from a couple years ago, I think another snake challenge would be nice. Below (from the description section to the end) I describe a "classic" snake challenge.

However, I want to differentiate this from the classic challenge. I am more than open to suggestions in the comments below. My idea is the following:

Make an "infinite" snake game. That is, every 10 points, the level changes and the snake is reset according to the following pattern:

--The nth level contains n obstacles in the form of the '#' character. These work the same as walls. They are randomly placed around the map, the difficulty is that they cannot create a situation where an ungettable 'x' exists. for example:

------------------------------
| #                          |  11
|                            |
|              oooooo        |
|              o    o        |
|              o    v        |
|              o             |
|                            |
|                            |
|    x                       |
|                            |
------------------------------

would be unacceptable because if an "x" were to spawn in the corner, it would be an automatic game over. Also, the barriers may not form a wall which closes off areas of the arena.

I can flesh out this idea more if you think it is any good.

Please Give Me Feedback On This Question

When I have a working question, I will begin work on a basic solution in C++.

Description

The goal of this challenge is to create a real time (non-buffered input) ASCII version of the popular game Snake .

The board is 10 newlines by 32 spaces. The boundary consists of the " | " and " - " characters.

The snake body is made of the "o" character.

The snake head is v,<,>,^ depending on direction of travel (intuitively)

The snake eats " x ".

For example a game board might look like:

------------------------------
|                            |  11
|                            |
|              oooooo        |
|              o    o        |
|              o    v        |
|              o             |
|                            |
|                            |
|    x                       |
|                            |
------------------------------

In the new game, the snake has three body segments and a head. It gains one body segment every time it eats an "x".

The score (the number of segments+head) should be displayed somewhere on the screen.

The starting position of the snake and the starting position of the "x" is left to the writer.

After an "x" is eaten, the snake gains a segment, and a new "x" must spawn. "x"s may not spawn in a set of predetermined coordinates. They must spawn "pseudo-randomly" in the loosest sense of the phrase. This means that they can spawn using a random number generator or their position may be simply a function of the snake's position or some such simple rule.

The snake moves according to nonbuffered user input according to one or both of the following layouts:

"W" - change direction up.

"A" - change direction left.

"D" - change direction right.

"S" - change direction down.

AND/OR

"UP" - change direction up.

"DOWN" - change direction left.

"LEFT" - change direction right.

"RIGHT" - change direction down.

Note that, as per the rules of snake, at a given instance of the game, only three options are available to the player:

-- Do nothing (and continue moving straight)

-- Turn 90 degrees

-- Turn -90 degrees

Therefore, at a given instance, two of the movement buttons should be unresponsive. E.g. in the above case, only right and left are responsive.

Snake movement follows the normal pattern. For those of you not familiar with it: Let segment zero, $$s_0$$ be the head and segment $$s_n$$ be the very end of the snake. In a given frame, the snake has 3 choices, go straight, go left, or go right (from the snake's reference frame). $$s_0$$ moves into one of these spaces based on user input. Then $$s_i$$ moves into the space taken by $$s_{i-1}$$ on the previous frame.

If an "x" is eaten, then on the next frame the new segment $$s_{n+1}$$ is placed where $$s_n$$ was on the previous frame.

The game ends when the snake head collides with the snake body or a with a wall.

Rules

1) Only languages which are available for free may be used. Libraries may be used (for i/o, etc), however the actual snake program must be written by you. (if library overuse is an issue, it will be determined by up/down votes)

2) The game must be playable (i.e. the framerate must be acceptable on most machines, as determined by readers)

3) The winner is the program using the smallest number of bytes that fits the above description.

4) If an online compiler is available, it is recommended that you link it with your code so that others may play your game.

ascii-artcodegolf

Answer 7

Machine Learning

If you give a downvote please say why! (otherwise how will I learn, thanks)

The task is to create a simple program that "learns"

-->The challenge is to create a program which:

(1) outputs 50 integers (1 at a time) and waits for input after each.

The input given will be 1 or 0 depending on whether the number is "good" or "bad" based on a predetermined pattern (see the pattern section for more information)

(2) The program will then output something to the effect of

<< Learning done. Ready for testing.

At which point it will wait for integer input.

(3) My script will then input 50 integers (1 at a time) and the program will read the integers and output 1 or 0 depending on whether it thinks the integer fits the pattern.

-->Types of Patterns

Patterns will be of the following types, in an unknown order

- is divisible by x (x no larger than 20)

- is greater/less than x (x no larger than 100)

- is a perfect square

- has exactly x prime divisors (x no larger than 3)

- is coprime to x (shares no common divisors with x except 1) (x no larger than 100 and not prime)

numbers above subject to change if a case is made in the comments

-->Scoring

Bots will be scored on correct answers to my script input. The score is equal to the total number of correct answers across all 5 tests. There is a max score of 250.

Since I do anticipate perfect scores, ties will be broken by golf score of the source.

Further ties will be broken by submission time.

-->Example of A Test

note: "in" is for my input. "out" is for machine output.

The rule is "even-good, odd-bad"

out<<  10
in>>   1
out<<  1901
in>>   0

... more lines like this ....

out<<  Learning Complete. Ready for Input.

in>>   12
out<<  1
in>>   87
out<<  0

... more lines like this ...

Say the machine got 47/50 correct on this test, then it currently has a score of 47. I would then proceed to test it with 4 different patterns. And sum its score on each test for its final score.

-->Rules

(1) you may not use external tables, i.e. have a library that contains table for all possible tests. However, your code may generate such tables.

(2) the bot may not exceed an average time of 2 seconds per output. This goes for both the learning and testing sections. I really don't want to have to spend over 15 minutes per test. The average is so that it can spend a bit of start-up time to generate tables if it needs to.

(3) Use of external libraries is permitted, although it should be clear that the bulk of the work is yours. (this will be determined by downvotes)

(4) Languages must have a free interpreter available. If they don't I won't be able to test them. This rules out MatLab, Mathematica, etc.

(5) other rules may be added as necessary.

Answer 8

Mutating variable

Output
n number of lines (where n is from 10 to 30, each run is random) where each line is either (all of the lines have to be possible)

1. Array of n random chars (or String with n random characters) made out of letters only
2. random int divisible by n (by int I mean a whole number of any kind)
3. random double whose first two decimal digits is n (by double I mean an number that has decimal digits) therefore for n=12 it will have format ###.12####
4. random boolean true or false (by that I mean 1 or 0)

No two consequent lines may be same type

Another requirement is that in your code may call print (or System.out.println or whatever you use to print to screen) only once.

This is code-golf, so shortest code wins.

By random I mean use your language's built-in random number generator,

Answer 9

Ceylon golfer (whitespace + comment removal)

As some people might have noted, I'm answering here often using Ceylon. This is usually done first writing a "normal" program, then slimming it down using whichever tricks I find, and at the last step remove all superfluous white space (and possibly also comments)

I want to automatize the last step.

Ceylon is syntax-wise a C-like language, so this golfer might be useful also for other languages. The details might differ, though.

This is similar to Remove Whitespace from a Java Program, but not the same, as Ceylon strings are a bit more complicated.

Details

A Ceylon program is a Unicode character stream, which can be lexically analized into a series of tokens, possibly separated by whitespace. (Only ASCII white space is allowed: space, tab, form feed (FF), line feed (LF), carriage return (CR).)

That whitespace is sometimes necessary – when otherwise the two tokens would stick together and form one token, or when a comment would become longer than before (but comments are to removed, too). Other whitespace can be removed.

Lines are terminated by LF, CR or a sequence of CR LF.

We have two kinds of comments:

• Multiline comments start with /* and end with */.
• end-of-line comments start with // or #! and end with the line (i.e. at the next line terminator).

Everything which is not whitespace or a comment is part of a token.

Tokens are of these forms:

• Identifiers or keywords start with a (uppercase or lowercase) letter and then can contain letters, _ and digits. They can also start with \I or \i instead. (Examples are true, Integer, a, helloWorld, example1234, \Iexample1234.)

• Literals:

  • numeric literals (decimal integer, hex integer, binary integer, formal floating point, shortcut floating point) have the form [0-9_]+[kMGTPmunpf]?|\$[01_]+|\#[0-9a-fA-F_]+|[0-9_]+\.[0-9_]+(e[+-]?[0-9]+|[kMGTPmunpf])? (where the _ is only allowed at certain places).

    (Maybe that can be simplified to [#$0-9][0-9a-fA-FkMGFPmunpf._]*, with the dot not being the last character. Not all such strings are valid numeric literals, but I guess you don't have to figure them all out. The details are in the specification linked above.)

  • Character literals have the form ' + single character (except " or \) or escape sequence + ', where an escape sequence is either a \{ + a name or code of a character + }, or a \ followed by a single (non-{) character.

    Examples: ' ', '←', 'a', '\'', '`', '\{#0020}', '\{#212B}', '\n', '\{ALCHEMICAL SYMBOL FOR GOLD}', '"', '\"', '\\', '/'.

  • String literals:

    • A simple string literal is " + a sequence of single characters (except ", \ and ` ) and escape sequences (see above) + "
    • An interpolated string literal (or string template) looks like a simple string literal, but can also contain `` + some non-string-code + `` inside the string. (In this non-string-code the whitespace and comment removal can be applied.)
    • A verbatim string literal is """ + a sequence of any characters, except """, + """. (There is no escape sequences or interpolation here.)

    There is further complication with multi-line string literals, but I guess for this challenge we can assume that there are no multi-line string literals.

    Examples for String literals: "", """""" (both the empty string), "Hello World!", "Escapes: \{#212B}, \{ALCHEMICAL SYMBOL FOR GOLD}", """non-interpreted Escapes: \{#212B}, \{ALCHEMICAL SYMBOL FOR GOLD}""", "some more escapes: \n, \r, \f, \t, \b, \\, \`, \', \"", "punctuation: ' ` \" and more text", """punctuation: ' ` " and even single \.""",

• A lot of symbols are punctuation and operators:

   , ; ... { } ( ) [ ] ` ? . ?. *. = => + - * / % ^ ** ++ -- .. : -> !
   && || ~ & | === == != < > <= >= <=> += -= /= *= %= |= &= ~= ||= &&=
  

  The grammar is such that whitespace adjacent to one of those punctuation tokens is never relevant, so it can be removed.

Challenge

Write a program which receives as input a valid Ceylon program, and outputs the same program, with all comments and non-essential white space removed.

Whitespace is essential when without it two tokens would be one token – this applies specifically to keywords/identifiers and numeric literals. In those cases replace any string of whitespace with a single space.

(I guess there are some cases like 10else where an integer literal can be joined with a keyword, but for safety it is better to always have a space in there.)

Of course, whitespace inside a string is highly relevant, so it should not be touched.

If a removed comment was the only thing between two keywords/identifiers, make sure to put a space in there.

---

Open questions

• I guess I should add some example inputs and expected outputs.
• How to score this? Simply as Codegolf, assuming there will be correct answers? Or give some example programs and see which entry succeeds to make them smallest?
• I guess most Ceylon programs to be golfed will actually be ASCII only – do we allow ASCII-only solutions, while giving a bonus for proper Unicode handling (in comments, strings, identifiers)?
• Do we require full programs, or allow also functions which take+return strings (or character streams)?
• Did I simplify the grammar not enough, or too much?
• I can imagine some bonuses for finding the shortest representation of an integer of float literal .. not sure if that is worth the complication.
• Another possible bonus would be to find the shortest way of representing a string literal (replacing some Unicode escapes by the actual characters, choosing between " and """, etc.).
• Do we want to handle multiline strings correctly? Maybe as a bonus?

• Another possible bonus would be to remove strings literals which are not passed or assigned to anything (these are often used for documentation comments) – but I'm not sure how to define that without specifying the whole grammar.

  (Those have leadings space in the following lines, up to the column where the literal started, which needs to be removed when lexing. If we change the alignment of the string literal, we need to adjust those spaces too. Here it can sometimes be useful actually not include a new-line before the string to minimize that indentation.)

Answer 10

Steganographic Image Encoding

code-golf graphical-output image-processing steganography

Write two programs, an encoder and decoder. Score is the sum of the source in bytes.

Encoder Specs

Input:

• a lossless 24-bit color image file
  • could be anything from BMP to PNG to PPM
• an arbitrary data file
  • undefined behavior if one attempts to encode a too-large file in a too-small image.
• an integer value, n, from 1 to 8, indicating the number of bits to use per subpixel.

Output:

An encoded image with the arbitrary data stored in the n least significant bits of the pixel data. The data must be stored in the pixels, i.e. not in some hidden metadata. How the data is serialized into the 3-D image space (height, width, color channel) is undefined.

Decoder Specs

Input:

• an image produced by the encoder
• the arbitrary file's length in bytes
• the same integer value the decoder took indicating the number of bits per subpixel.

Output:

• the identical arbitrary data file as was provided to the encoder

Requests for Comment:

• Fix n to 1?
• Encode the length/LSB's used in the image so you don't need to specify them again. (e.g. fixed format for a couple pixels to define it?) Requirement/Bonus?
• Maybe have the arbitrary data file be another image of the same dimensions, a la the Wikipedia example (cat in a tree)? That could be kinda boring though; some very simple array operations could do it all. Or that could be clever. In that case, there's necessarily data loss of the hidden image.
• If n was one and this only required an encoder, it would be the same as this, but this requires a matching decoder. One way encoding challenges I find dull.
• I'd be fine with using image libraries to load/save the image

Answer 11

code-golf

Objective

Given a string in Markdown, determine how much of the string is in bold and italic.

Test Cases

**Bold** --> 0
*Italic* --> 0
**_BI_** --> 2
__*abcde*__ --> 5
This is in **bold and _this_ is in italic** --> 4
\**_BI_** --> 0
\\**_BI_** --> 2
This is not in ___ bold-italic ___ --> 0

Answer 12

Implementations of linked lists

Given the source code of a function or method to delete the first node having value x if existed, from a non-cyclic singly linked list, in a specific programming language. Write a program or function (not necessarily in the same language) to decide what kind of implementation it is.

You don't have to check for all the cases. But the more intelligent your code is, the better.

The possible implementations need to be checked are:

Pointer of pointers

(Spec and examples to be added.)

Head node

(Spec and examples to be added.)

Moving the data

(Spec and examples to be added.)

(And maybe some others.)

---

Possible winning criteria:

• Just popularity-contest.
• Something like code-bowling where a submission is valid if no shorter programs can do all the things documented in the answer.

Answer 13

Would someone like to write a crontab puzzle?

I have just asked for a software that displays all times at which a cronjob runs. As I think more about it, this might be a nice golfing question.

Unfortunately I'm not too familiar with the crontab specification, especially when it comes to combining operators such as

*/15,34,49-52 * * * * /path/to/command

Is that suitable for code-golf at all? If someone or a group of people would define it as a puzzle, I'd be glad to see it.

Starting point:

The program

• takes a crontab line as input
• checks if it is valid or not
• if valid, from now on lists the next execution times
• limited to a user definable amount

E.g.

program -n 10 30 17 * * *

produces 10 lines of output (assuming today is 2015-10-22 18:00)

2015-10-23 17:30
2015-10-24 17:30
2015-10-25 17:30
2015-10-26 17:30
2015-10-27 17:30
2015-10-28 17:30
2015-10-29 17:30
2015-10-30 17:30
2015-10-31 17:30
2015-11-01 17:30

Answer 14

Word Game KotH king-of-the-hill

First of all, I don't know what this game is called (or if it even has a name), but it's a modification of a game I've played a few times on road trips, especially with my family. I'll be thinking of a better name.

Any suggestions at all are very welcome.

How It's Played

There are 5¹ bots playing per game. At the beginning of the game, they are given a collection of letters (which is not necessarily a word), for example "a" or "jet." The bots take turns in a predetermined order. When it is a bot's turn it is passed the current word(s) and has four² options:

1. It can change a single letter to any other letter.
2. It can add a single letter to any position in the word.
3. It can swap any two letters in the word.
4. It can split the word at any point.

If you didn't infer already, these actions are allowed with the caveat that their result is a valid word or two valid words, if the bot chooses to split. The game ends when the combined lengths of all the words in play are 3 times the length of the longest word in the dictionary used (e.g. if "onomatopoeia" is the longest word, the max length would be 36 letters since it has 12) or when only one bot remains. The bots are scored on how many turns they last^*, and the winner of the game is granted a bonus³.

*The turn they lose on is not counted, so if the bot were to lose on its first turn it would have lasted 0 turns.

A word is valid if it is both in the dictionary and hasn't been played before.

Bots should take a reasonable amount of time in making their plays (no more than a few seconds).

Available Methods

isValid(word) returns a Boolean value (whether the word is valid or not).

getDictionary() returns the entire dictionary as a single string.

getPreviousPlays() returns the words previously played as an array (one word per element).

Once any of the following methods are called, the bot's turn is over:

change(index,letter) changes the letter at that index to the letter provided. This method cannot change a space to a letter (to prevent stalling).

insert(index,letter) inserts the provided letter at the provided index.

swap(index1,index2) swaps the letters at index1 and index2.

split(index) splits the word into two by inserting a space at the specified index. Both of these words have to be valid⁴

If any of the calls to these methods are invalid, the bot is disqualified for that game (treated as a loss).

Author's notes

1. Basically a random number I determined; I don't know if it's too big or small.
2. Is four too few to make this challenge interesting?
3. This bonus is undetermined as of now, but I'd say 2 points tentatively. I'm also a bit unsure as to whether that is a good scoring method. Should it just be on victories or position in victory (i.e. first, second, third, etc. place)? I'm also worried that this might encourage users to submit bots that collaborate to last as many rounds as possible.
4. Would it be more interesting if this ignored validity? e.g. if you have candies dog as the two words, splitting candies into can and dies would be valid even if either of those words had been played before.

I haven't done a KotH submission before, so I'd love feedback as to how to improve this.

Unimplemented Portions

Controller

This is the big unimplemented portion: I want to get feedback on the idea as a whole before diving into programming out a controller.

Scoring

I'm still unsure as to how the games should be scored.

Answer 15

Create CHIQRSX9+ Analogue Program.

meta-golfcode-golf

Your task is to create a program in same language, that when given a CHIQRSX9+ will print a that analogue. That analogue program will do similiar thing that CHIQRSX9+ program do. There's exception though. There's may be more than 1 instruction. Then it's meant to be executed

1. C => Read until empty line and print all entered lines, including empty line.
2. H => Print "Hello, world!"
3. I => Read input until a newline then return that analogue
4. Q => Print the analogue program source code. (Not the entered one)
5. R => Read input until a newline then print that string after doing ROT-13
6. S => Read comma separated number until newline and sort that.
7. X => For this, X have undefined behavior.
8. 9 => Print 99 Bottles of beer with correct pluralization.
9. + => Increment Accumulator.

Printing instruction(C, H, I, Q, R, S, and 9) begin in a new line. After everything is printed, accumulator count is written at new line. Final newline is optional.

Example

If there's program X written in Haskell, then

X
CH
>main=interact$(++"\nHello, world!\n0").unlines.takeWhile(/="").lines

Which when compiled (Example as W) will do that

W
This is a line
This is another line

>This is a line
>This is another line
>
>Hello, world!
>0

Another example for Q

X
Q
>main=putStr(s++[';','s','=']++show s);s="main=putStr(s++[';','s','=']++show s)"

Yet another example

X
H+
>main=printStr"Hello, world!\n1"

Here is for indication of output. DO NOT print it.

Sandboxing Question

How about scoring. I want to reward short produced program. However, shorness of producing program is also counted. I guess just 10A+5B+C. Where A is length of original source code, B is length of "QQQQ" analogue program. C is length of "CHIQRS9+".

Answer 16

Goal

The goal is to stitch several ordered lists of numbers into a single list that contains each of those lists as a contiguous sublist, with the numbers in the same order without gaps. The resulting list should be as short as possible.

Input

n ordered lists of numbers between -2^63 and 2^63-1

Ouput

A minimum-length list so that each input list appears within that list with its elements in the same order without gaps

Example

Input:

[1, 2, 3] [3, -38, 23424, 292] [0, 1, 2] [-38]

Output:

[0, 1, 2, 3, -38, 23424, 292]

The output contains each of the input lists:

[0, 1, 2, 3, -38, 23424, 292]
   [1, 2, 3]
         [3, -38, 23424, 292]
[0, 1, 2]
            [-38]

Answer 17

Hello, World! Fitted in cases.

code-golfhello-world

Your task is to take a line of input and print Hello,world! multiple times fitted to length of input. The cases of that character is fitted to input in same position(except shifted from deletion). If the corresponding character is non-alphabeth, you must use default case(lowercase except for "h" that is uppercase). And for punctuations, if the corresponding character is not punctuation, it will deleted. And if the corresponding character is space, the the ouput is space but it doesn't skip the "Hello,world" writing.

Example

Hello, world!
Hello, world!

About punctuation deletion and space insertion

I have a dog. I name it Underdog.
H ello w orld H ello wo Rldhellow

Explanation

Ihaveadog.InameitUnderdog.
Hello,worlD!hello,world!hellow
Helloworld!hello,World!hellow
HelloworldHello,wOrld!hellow
HelloworldHellowoRld!hellow
HelloworldHellowoRldhellow

Other examples

.....&^&%&*%&(&)^$#()&#()&@#)*%)#1-
Hello,world!Hello,world!Hello,world

UPPERCASES
HELLOWORLD

lowercases
helloworld

Abdeg,fGhiJ.
Hello,wOrlD!

Example Program

Here is ungolfed version of example program in Python. If there is error, correct me.

p=readline()
h="Hello, world"
i=0
k=""
for a in xrange(len(p)):
    if p[a]==" ":
        k=k+" "
        continue
    if isUpper(p[a]):
        if isAlpha(h[i]):
            k=k+upper(h[i])
        i=i+1
        continue
    if isLower(p[a]):
        if isAlpha(h[i]):
            k=k+lower(h[i])
        i=i+1
        continue
    k=k+h[i]
    i=i+1

Sandbox Question

This language is surely need to be fixed.

Answer 18

How am I doing?

popularity-contestascii-art

My boss is a flashy sort of fellow. He likes all things animated.

He's asked me to write a progress bar to show the completeness of our super-secret project.

Now with me being me, I'm getting you to write this for me and showing the best one to my boss.

Task

• Output a progress bar to stdout.
• Whenever a newline is sent to stdin, increase the percentage on the percentage bar by 1%
• If not already enabled and if possible in your language, set the terminal mode to non-echoing (stdin doesn't automatically get shown, think like when your typing in your password for sudo)
• You may not assume the cursor is in a certain position, it must produce a progress bar relative to where you started the program (no absolute jumps)

To help you, you may use ANSI escape codes, ANSI colour codes and any UTF-32 unicode points.

The winner is the entry with the most upvotes.

Sandbox Notes:

• Is this too broad? - I'm sticking to ANSI only but I'm not saying anything else about what it looks like.

Answer 19

Kaprekar Transformation

Kaprekar Transformation is an transformation a number by following that instruction:

1. Take n-digit integer.
2. Sort it anscending and descending.
3. Subtract the largest number and smallest number.

Your program have to do this:

1. Take 1 number, x.

2. Output all possible cycle and fixnums for doing repeated x-digit Kaprekar Transformation on all possible input. Rotation is considered same. So it is invalid to print:

   [00],[09,81,63,27,45],[81,63,27,45,09]

The output is a list consisting of list representing the cycle. You may using any style of list and even intermix it with restriction that it should not be ambigous. For example, comma separated item with item using comma separated item with enclosing bracket is OK, but not comma separated item with item using comma separated item without enclosing bracket.

Example:

8
>[00000000],[43208766,85317642,75308643,84308652,86308632,86326632,64326654],[63317664],[64308654,83208762,86526432],[97508421]

Or

>[00000000],[[43208766,85317642,75308643,84308652,86308632,86326632,64326654],[63317664],[64308654,83208762,86526432],[97508421]]

Answer 20

Stupid leaks

Considering how immensely successful my last two challenges have been, I'll do a different style this time.

Drip, drip, drip, drip...

It's the year 3000. Due to clean air shortages, a system was created that turns water into air. However, that caused a water shortage (don't you love progress?). Therefore, a new (expensive!) system was created to convert the air back into water.

All that to say that water prices have skyrocketed.

And yet, here you are, stuck with a leaky faucet. Plumbers are expensive, but if you do it yourself, you have to order the parts online and wait for them to get here. You need a way to determine what is cheaper: calling a plumber and getting it fixed in a day, or buying the parts online but having water leak until they get here.

The input

You need to take seven positive numbers as input:

• The price of water per gallon g.
• The number of drops leaking per hour d.
• The number of gallons wasted per drop z. This will always be a floating-point number less than 1.
• The price of calling a plumber to fix it p.
• The price of ordering the parts online o.
• The number of hours it takes for the plumber to fix the leak l.
• The number of hours it takes for the parts to get here s.

Only g, z, p, and o can be floats; all the rest will be counting numbers (integers greater than 0).

The task

The gallons of water wasted per hour from the leak is d*z*g. For the sake of brevity, let's call that rate R. If R*l+p is less than R*s+o, then you should print/return DIY!. If greater than, print/return Call the plumber!. If equal, print/return Whatever....

Precision

Floating-point precision through calculations is very...weird. Basically, your program can use whatever your language's default is. If you're using a language where the default floating-point type has infinite precision. If your language's default floating-point type can lose precision throughout calculations (like in Python, where .1+.1+.1+.1+.1+.1+.1+.1 != .8), then that works, too.

Short version: floating-point semantics and precision are however your language is by default.

Scoring

Code-golf. Shortest wins. Standard loopholes banned.

Answer 21

Show How a Regex Is Matched

What your program or function should do:

1. Accept input of two strings; let's call them r and s.
2. Determine whether r is a valid regular expression (you can use any common definition of regex for this purpose, or any common definition of regexes but with lookahead and lookbehind removed; indicate which you're using). Otherwise, don't output.
3. If so, determine whether s matches r as a regex. Otherwise, don't output.
4. If so, output/print, in order, the part of r matched by each character of s, and also the part of s that matches it.

Note: You may use your language's regex-matching library for this.

Example:

Using PCRE; my inputs and outputs are r first and then s.

^.el*(o.*)*d\b and Hello, world!
→ ^.ello......d\b and Hello, world

.\1\W and 800-555-1212
→ ..\W and 00-

\b and a
→ \b and empty string

\d and a
→ no output (it doesn't match)

code-golfregular-expression

---

_{First floated in chat.
Not a dupe of Compile Regexes (which asks you to match regexes whereas this allows you to use the resources of your language to do so).}

Answer 22

Python assembler

code-golf

Python is a hybrid interpreted language. It first gets compiled into byte-code and then gets interpreted.

What does this byte-code look like you may ask? The dis module disassembles python code. Source code for dis module here

print "Hello, World!"

Gets disassembled into the following assembly.

  1           0 LOAD_CONST               0 ('Hello, World!')
              3 PRINT_ITEM
              4 PRINT_NEWLINE
              5 LOAD_CONST               1 (None)
              8 RETURN_VALUE

The output is divided in the following columns:

1. the line number, for the first instruction of each line

2. a labelled instruction, indicated with >>,

3. the address of the instruction,

4. the operation code name,

5. operation parameters, and

6. interpretation of the parameters in parentheses.

The disassembly of a basic for loop

for i in range(10):
    print i

gives

  1           0 SETUP_LOOP              25 (to 28)
              3 LOAD_NAME                0 (range)
              6 LOAD_CONST               0 (10)
              9 CALL_FUNCTION            1
             12 GET_ITER
        >>   13 FOR_ITER                11 (to 27)
             16 STORE_NAME               1 (i)

  2          19 LOAD_NAME                1 (i)
             22 PRINT_ITEM
             23 PRINT_NEWLINE
             24 JUMP_ABSOLUTE           13
        >>   27 POP_BLOCK
        >>   28 LOAD_CONST               1 (None)
             31 RETURN_VALUE

Your task:

Given some python code that has been disassembled, recreate the original code object as close as you can. You can take the disassembled code through any method you chose.

Your program will output all the arguments to recreate a python code object

That is to say your program will output the following

0,             
0,      
nlocals,              
stacksize,            
0,                
codestring,           
consts,               
names,                
varnames,             
"a string here",            
"another string here",
0,        
lnotab,               
(),             
()

You can work out the variables listed above but you have to output it all, even the constants.

• nlocals - The number of local variables
• stacksize - The maximum number of values held on the stack at once
• codestring - A binary containing all the opcodes and their arguments
• consts - A tuple of constants
• names - A tuple of global variables
• varnames - A tuple of local names (length of nlocals)
• lnotab - A tuple containing a map of bytecode positions to line numbers

You may use the following code to disassemble a .pyc file:

import sys, dis, marshal

with open(sys.argv[1], "rb") as code_f:
    code_f.read(8) # Magic number and modification time
    code = marshal.load(code_f)
    dis.dis(code)

This is code-golf, the shortest code in bytes wins

Sandbox notes

Wow that was a long one. Perhaps too long?

Is the spec completely tight?

Should I explain anything further?

Am I making it too hard for non-python entries to take part?

Should I only make it a requirement to reassemble code without any functions/classes? I'm pretty sure dis doesn't show all that.

Answer 23

Print a sourcecode

code-golfquine

Given 2 inputs(First input is truthy/falsy, second input is program in same language as submission):

1. If the first input is truthy then transform the second input into same program but printing the source code(After modification) first.
2. If the first input is falsy then transform the second input into same program but after the program finished it prints the source code(After modification). If the program doesn't halt, you may or may not modify the program.

It's code-golf, so the shorter answer is the winner.

For example in CJam, I don't write the program to do this. (> means output)

0 q
>{"_~"q}_~
0 0 1{_@+}11*;
>{"_~"0 0 1{_@+}11*;}_~
1 q
> {q](\o"_~"}_~

Answer 24

Vigenère Cipher

Write a program that is capable of breaking a text encyripted using Vigenère cipher encyription.

Goals:

• Take encripted text from STDIN and write plaintext to STDOUT.

Limits

• Keyword will always be 3 letters in length.
• Plaintext will always be in between 5-10 letters in length (inclusive).
• All Plaintexts, Keywords and Encyripted Texts will be in English.

Scoring:

This is a code-golf. Shortest code in bytes wins.

---

I'm not sure if this is a valid and solvable question, so any suggestions are welcomed.

Answer 25

List Style Converter

[code:golf]

Task

Given a list, format it into list of the choice of the input. The list will be list of item defined below, but it can be multidimensional.

List Styles

There is 2 list separators:

1. Space

2. Comma

   For one dimensional list, only one separator is accepted. Space and only space between item is considered as separator. It is impossible to have more than 2 dimension without enclosing list of second dimension or third dimension. when parsing list, comma takes lower precedence and it is parsed with least dimension as possible. Space is optional between ] with [; } with {; and ) with (

   There is 3 list enclosure:

3. [...]

4. (...)

5. {...}

   Closing bracket must be present.

Item

There is 2 types of item, another list or those following regex [0-9a-zA-Z]* or everything enclosed with single quote or double quote. If enclosed with single quote, it can contains double quote and vice versa. There is no zero-length item

Here is valid non-list item

98Az
Helloworld
"Hello, world!"
"It's house."

Here is the list

Hello, World!
Space then it is list
()

Here is invalid item.

!$%#%^$*%%^&%^&$%#:;,./<>?
Helloworld!

Input

The input consist of string of number then space then list as defined above. The number indicates the output format.

There are n digit of number where n is dimension of the input array. each number correspond with this one. (Table formatting needed). The dimension is counted from outer into inner. You may assume that there is no two 0 or 1 without being separated by 2 - 7.

1. 0 = unenclosed comma list
2. 1 = unenclosed space list
3. 2 = parantheses enclosed comma list
4. 3 = parantheses enclosed space list
5. 4 = square bracket enclosed comma list
6. 5 = square bracket enclosed space list
7. 6 = curly bracket enclosed space list
8. 7 = curly bracket enclosed space list

Output

A identical list but with formatting changed according to input (i.e. each item it list is identical). Space not between list is allowed

Test cases

> denotes output # denotes comment

6 Hello, world
> {Hello world}
5 (1, 1, 2, 3, 5, 8, 13, 21)
> [1, 1, 2, 3, 5, 8, 13, 21]
#Alternatively
> [1,1,2,3,5,8,13,21]
#Or
> [ 1,1, 2,3, 5,8, 13,21 ]
#But it is invalid
> [1,1, 2,3, 5,8, 1 3,2 1]
#Also
> [1,1,2,3,5,8,13,21,]
10 Hello, I am doctor
#Parsing rules that space separator bound tighter
> Hello I,am,doctor
01 Hello, I am doctor
> Hello, I am doctor
0 "Not to be confused be space or comma in a quoted item"
> "Not to be confused be space or comma in a quoted item"
51 [1,2] [3,4]
> [1 2,3 4]
51 [1,2][3,4]
> [1 2,3 4]

Sandbox Question.

The format needs helps. Needs pointing when there is ambiguity.

Answer 26

Triangularity

This is a challenge where you have to work out the length of a given w and h.

To qualify as a correct solution:

1. The program uses STDIN to get the values of w and h.
2. The program uses STDOUT to output the value of a in the above diagram.

The shortest code in bytes wins.

Tags: code-golf, maths

Answer 27

Wildcard Golf

Introduction

I've read this problem long time ago somewhere but I still don't know what's the best solution, so I'm posting it here. I don't remember the original author or wording so here is all in my own words.

This is different from regex golf because only two wildcards, * (equivalent to the regex .*) and ? (equivalent to the regex .), are allowed.

Challenge

You are given two lists of strings. You need to generate the shortest wildcard that matches all strings in the first list (the wanted-list) and none in the second list (the unwanted-list). In the wildcard, you can use * to match 0 or more chars and use ? to match any one char.

For simplicity we can assume that inputs only have lowercase English characters and each string won't be longer than 100 characters. But the list can be very long (like several thousand), so speed of your program is important.

The correct answer that has the lowest average-case theoretic time complexity wins. In a tie, an easier-to-read answer wins.

Example Input and Output

Input:

• Wanted list: abacum, academ, alarm, adam
• Unwanted list: alien, african, atom

One possible output: a?a*

I'd also like to hear about how to approach this problem, and how to prove the theoretic lower bound of time/space complexity.

---

I'm new to this so comments are welcome. I'm not sure if my winning criteria is clear and practical. Also I don't know what tags I should put there. This is not a code-golf question.

Answer 28

C++ Expression Matching

code-challenge c++ arithmetic

So, I like C++. And I like regex matching puzzles (heck, "regex golf" is what first got me lurking on this site). Might as well try to sort of combine the two!

Rules

Write a full program that takes as input two lists of zero to five integers in the range [1, 127], and outputs a string representation of a C expression that evaluates to nonzero / true for all integers in the first list, and zero / false for all integers in the second list. Input can be taken in any convenient form.

As a special case, if the second list is empty, then the expression returned must evaluate to true for only the integers in the first list, and false for all other integers in the range [1, 127]. Likewise, if the first list is empty, it should evaluate to false for the integers in the second list, and true for all others in that range.

The program will not receive two empty lists as input. If both lists are non-empty, there are no requirements on the result of the output when evaluated with an integer not in the input. (any return value is fine, as is undefined behavior, division by 0, etc).

The following tokens may be used in the expression:

• Integer literals in decimal, hex, or octal, with optional U and/or LL suffix to denote unsigned / long long ints.
• A single int variable, which will contain each of the integers from the input in turn. The variable can have any legal variable name.
• Any of the unary operators + - ! ~
• Any of the binary operators + - * / % << >> < > <= >= == != & | ^ && || ,
• The ternary operator ?:
• Parentheses.
• Operators that mutate their arguments (++ --, = += -= etc.) are not allowed.
• Character literals ('a', '_', '\0', etc.) are not allowed.

Some examples of possible outputs:

true            false           sample expression
[1, 3, 5, 7],   [2, 4, 6, 8]    c%2
[5, 6, 10],     [2, 8, 16]      t&~-t
[7, 14, 21],    []              22>x&!(x%7)

(TODO: Specify undefined / implementation-defined behavior details? My test program assumes 32-bit ints / longs, 64-bit long longs, and "nice" two's-complement signed overflow / conversion.)

This challenge is code-challenge; your score is determined by the total number of characters in the outputs for these ten randomly-generated inputs: (TODO).

Bonus: Subtract 15 from your score if the output expression evaluates to 1, not just nonzero, for all 'true' inputs.

Sandbox Questions

Welp, turns out my "Round Fractions" question from earlier is pretty much a subset of "Closest fraction". So here's another idea I've been tossing around since the one challenge I answered in C a while back (Area of an ASCII Polygon).

This is still very much a work-in-progress spec, though; some questions I have:

• I believe this could be tagged as C rather than C++; the only difference I'm aware of is the ternary conditional's precedence, and given that no assignment operators are allowed, it might not make a difference.
• I'm not sure what tags would go best on this (is it kolmogorov-complexity if the output isn't fixed?)
• I imagine there should probably be some additional constraint to prevent theoretically optimal but impossibly slow brute-force searches.
• The range [1, 127] is kind of arbitrary; my thought is that it should be able to handle anything in ASCII range + whitespace characters, but not much more than that, so as to make the special cases less restrictive.
• Would there be a way to spin this off as code-golf, if establishing run-time conditions is too arbitrary?

I'm mostly done writing a program to test the output expressions; just need to do a bit more testing.

That's pretty much it; hopefully this is enough to work with for feedback. Thoughts / comments?

Answer 29

Typographic Chemistry

Inspired by this: https://xkcd.com/1442/

Task

You must make a program or function that take input a string from STDIN and output the possible allowed reactions (1 point per unique reaction, see also "Score" below)

Rules

A chemical reaction is allowed if all the "legs" of the elements are used, i.e., there are no unpaired "legs". A "leg" is just the end of a curve in the typographic print of the chemical symbol (see the comic and it should be clear). So for example:

Carbon - C - 2 legs

Oxygen - O - 0 legs

Hydrogen - H - 4 legs

Nitrogen - N - 2 legs

Potassium - K - 4 legs

Phosphorus _ P 1 leg

An element can be rotated, reflected but not stretched in any way, so that the only possible bonds are (here I don't know how to rotate the chars, if somebody can help it would be welcome):

$$CH \;\mathrm{(with\;the\;C\;on\;top\;or\;bottom\;rotated\;by\;90\;degrees)}\\CK \;\mathrm{(with\;the\;C\;on\;top\;or\;bottom\;rotated\;by\;90\;degrees\;or\;to\;the\;right\;rotated\;by\;180)}\\ HK\;\mathrm{(on\;top\;of\;each\;other\;or\;on\;the\;side\;rotating\;one\;by\;180)}\\ NN\;\mathrm{(with\;one\;reflected\;has\;two\;legs\;on\;top\;and\;two\;diconnected\;legs\;on\;bottom)}\\ P\;\mathrm{(with\;anything)}\\ O\;\mathrm{doesn't\;bond}$$

These are the only possible elements passed from STDIN. Notice that the difference between H and K is that K can bond also laterally with a C.

Extra Rule

If no reaction is possible, the output should be equal to the input

Score

1 point per reaction. Bonus: X3 the score if you can print the reaction diagramatically, i.e. print the shape of the molecule (like in the comic)

Example

$$Input \rightarrow Output\\ C\,C \rightarrow (C_2)\\ N \, N \rightarrow N \, N\\ C\,N \, N\,P\,P \rightarrow (C N_2 P_2)\\ C\,C\,K \, H\,H\rightarrow (KC_2H_2)\\ C\,H\,O\rightarrow C\,H\,O $$

Answer 30

Note: I think the question is fine. I just need some more testcases for it.

---

---

You are given the priority order of alleles for a particular trait. For example,

A B
O

means that A and B are equally dominant and O is recessive to both of them. An organism has exactly two alleles, but only the dominant trait(s) is/are expressed. So an organism with gene AO will express only A but an organism with gene AB will express both A and B. An organism with two same alleles will express that allele only.

Each offspring will receive two alleles - one from the mother and the other from the father. So if the initial parents are AB and AO, the offspring formed will be:

AA - 25%
AO - 25%
AB - 25%
BO - 25%

Expressed traits will be

A - 50%
AB - 25%
B - 25%

Offspring of one generation may breed only with a single member of the opposite sex in the same generation during its lifetime. Assume for the sake of this challenge that every male finds a random female in the same generation and has exactly two children - one male and one female. Siblings may interbreed. Note that, except for the first generation, we can ignore the sex of the individuals as their sex chromosomes assort independently of their other characteristics.

Input

• Priority order of all alleles (may include unnecesary alleles)
• Genotype of every organism in initial generation
• Number of generations created
• Any one allele
• (Optional) Number of lines of input for priority order (for languages like C++)

Output

• Probability of the specified allele existing in a randomly selected individual in the specified generation (accurate to three decimal places)

Challenge

• Once two/three answers are posted, I'll use the same testcases in all of them to see which of them are faulty.
• After a week (or I could prolong the deadline) I will upload a lengthy test case in a few days. The code that solves it in the fastest time wins.

Sample data (Some simple testcases)

#1

A
B
C
Male(s) - AA
Female(s) - AB
5
C

Output 0

#2

A
B
C
Male(s) - AA
Female(s) - AB
2
A

Output 0.75

#3

A B
C D
Male(s) - AC,BD
Female(s) - AC,BC
1
C

Output 0.125