Sandbox for Proposed Challenges

Question

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.

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Answer 1

PPCG Handwriting OCR code-challenge test-battery

(insert logo here once I make it)

Given an image consisting of handwritten text, output the text that is written. The image of the handwritten text will be generated by taking characters from one or more handwriting samples given by PPCG users.

Rules

• You may not hardcode your program to only recognize the samples in the corpus.
• There will be sufficient spacing between characters to avoid ambiguity.
• Only ASCII alphanumeric characters (those matching the regex [A-Za-z0-9], i.e. uppercase and lowercase English letters and digits) will be present in the input.
• Inputs will be formed by concatenating individual characters from the handwriting samples.
• The test cases used for scoring may be modified at any point if I feel it is necessary to do so. Reasons may include but are not limited to: needing more test cases to have a single winner, removing problematic test cases, and fixing errors in test cases.

Aside from the above considerations, there are no guarantees on the appearance of the handwriting, as these are actual handwriting samples and thus can have drastic variances.

Score

Your score will be the number of test cases that are correctly recognized, divided by the total number of test cases. The highest score wins. In the event of a tie, the first submission to reach the high score wins. Additional test cases may be added to break ties.

Handwriting Samples

This Imgur album contains the handwriting samples, as well as the names of the users who contributed them.

---

I've made a chat room for submitting handwriting samples. The more samples I get, the better this challenge will be, so please take a few minutes and submit a sample!

Answer 2

2 Spooky 4 Me

In terms of halloween, some things are just too spooky for me... Feel like we need some serious doots from skeletons to fuel our hallowed weens. So, in the spirit of that end, print the following, exactly as it is shown, if and only if the input does not equal "DOOT" (in all caps ONLY):

               _.---._
             .'       '.
             :)       (:
             \ (@) (@) /
              \   A   /
               )     (
               \"""""/
                '._.'
                 .=.
         .---._.-.=.-._.---.
        / ':-(_.-: :-._)-:' \
       / /' (__.-: :-.__) '\ \
      / /  (___.-' '-.___)  \ \
     / /   (___.-'^'-.___)   \ \
    / /    (___.-'='-.___)    \ \
   / /     (____.'='.____)     \ \
  / /       (___.'='.___)       \ \
 (_.:       '---'.=.'---'       :._)
 :||        __  _.=._  __        ||:
 :||       (  '.-.=.-.'  )       ||:
 :||       \    '.=.'    /       ||:
 :||        \    .=.    /        ||:
 :||       .-'.'-._.-'.'-.       ||:
.:::\      ( ,): O O :(, )      /:::.
|||| '     / /''--'--''\ \     ' ||||
''''      / /           \ \      ''''
         / /             \ \
        / /               \ \
       / /                 \ \
      / /                   \ \
     / /                     \ \
    /.'                       '.\
   (_)'                       '(_)
    \\.                       .//
     \\.                     .//
      \\.                   .//
       \\.                 .//
        \\.               .//
         \\.             .//
          \\.           .//
          ///)         (\\\
        ,///'           '\\\,
       ///'               '\\\
      ""'                   '""

---

However, if the input DOES equal "DOOT", in all caps only, print this instead:

               _.---._
             .'       '.
             :)       (:
             \ (@) (@) /
              \   A   /
               )     (
               \"""""/
                '._.'          ' ''''    _''|
                 .=.       @=====***===::_  |
         .---._.-.=.-._.---. (( \-@|_) )) `.|
        / ':-(_.-: :-._)-:' \ ]--------'"
       / /' (__.-: :-.__) '\ \   ||:
      / /  (___.-' '-.___)  \ \  ||:
     / /   (___.-'^'-.___)   \ \ ||:
    / /    (___.-'='-.___)    \ \||:
   / /     (____.'='.____)     \ ||:
  / /       (___.'='.___)       \||:
 (_.:       '---'.=.'---'       :._)
 :||        __  _.=._  __       
 :||       (  '.-.=.-.'  )      
 :||       \    '.=.'    /       
 :||        \    .=.    /      
 :||       .-'.'-._.-'.'-.       
.:::\      ( ,): O O :(, )   
|||| '     / /''--'--''\ \    
''''      / /           \ \
         / /             \ \
        / /               \ \
       / /                 \ \
      / /                   \ \
     / /                     \ \
    /.'                       '.\
   (_)'                       '(_)
    \\.                       .//
     \\.                     .//
      \\.                   .//
       \\.                 .//
        \\.               .//
         \\.             .//
          \\.           .//
          ///)         (\\\
        ,///'           '\\\,
       ///'               '\\\
      ""'                   '""

---

Rules

• Trailing newlines and spaces are allowed.
• The design is horizontally symmetric, if you find inconsistencies let me know.

---

Doot it up, and enjoy!

code-golfascii-artkolmogrov-complexity

---

(Yes, I'm going to make it more official when posting on the actual SE)

Answer 3

Check equation proofs in a ring

code-golf math logic parsing decision-problem

The recent proof-golf to prove that (-a)×(-a) = a×a attracted a number of faulty submissions, because there wasn't an easy way to verify the proofs. So, let's write some proof checkers.

Input

Your program should take a sequence of strings representing expressions in a ring. Valid expressions consist of:

• Single-lowercase-letter variables (a to z)
• Two constants: the additive identity 0 and multiplicative identity 1
• Compound expressions: (X+Y), (X*Y) and (-X), where X and Y stand for subexpressions. (The parentheses must always be present, and there must be no whitespace.)

Task

Your program should check whether:

• All strings except the first and last represent valid expressions.
• Each expression (after the first) can be obtained from the preceding expression, by substituting one of the ring axioms in the expression exactly once.

Output truthy if these conditions are met. Otherwise, output falsey.

You may assume that the first and last strings in the input are valid expressions. But your program must check the intermediate strings.

The ring axioms

For this challenge, use the following substitution rules (and do not use any others). Substitutions can go both left-to-right and right-to-left.

1. (X+(Y+Z)) = ((X+Y)+Z)

2. (X+0) = X

3. (X+(-X)) = 0

4. (X+Y) = (Y+X)

5. (X*(Y*Z)) = ((X*Y)*Z)

6. (X*1) = X

7. (1*X) = X

8. (X*(Y+Z)) = ((X*Y)+(X*Z))

9. ((X+Y)*Z) = ((X*Z)+(Y*Z))

Scoring

Proof checkers are traditionally small, so that people can review them easily. Therefore, your program should be written in as few bytes as possible.

Meta comments

Is the input format fair for most languages and approaches?

Usually, code-golf problems should not require input validation. However, I thought it would be appropriate behaviour for a proof checker. I think the current spec still accommodates regex-based solutions.

The format for the original challenge also listed which axiom was used for each step. I could include this but I doubt that it improves the challenge much.

Test cases

Valid proofs

(0+a)
(a+0)
a

(a*(-1))
((a*(-1))+0)
((a*(-1))+(a+(-a)))
(((a*(-1))+a)+(-a))
(((a*(-1))+(a*1))+(-a))
((a*((-1)+1))+(-a))
((a*(1+(-1)))+(-a))
((a*0)+(-a))

Invalid proofs

These proofs are missing intermediate steps.

(0+a)
a

(-0)
((-0)+0)
0

((a*0)+(-a))
(0+(-a))

This is simply untrue, so no proof should ever be accepted.

(a*b)
(b*a)

Invalid expressions

Your proof checker should reject if these appear partway through a proof.

a+b

(a+-b)

(a + b)

1+

42

Answer 4

ASCII Stock Exchange answer-chainingcode-challenge

At the ASCII Stock Exchange, each character has a price. If a character is used more often, its price rises, otherwise the price decreases over time.

Initially, each character has price 10. [Meta: Is this too low/high?] After each answer, the prices change as follows:

• Each character that is not used in the answer's code has its price decreased by one, except when the price is already one, in which case it stays one.
• If a character is used n-times, then its price increases by n.

We define the score of a piece of code as the sum of the prices of its characters.

Example

For the sake of simplicity, we only consider characters A, B and C for this example. The challenge itself works with all bytes from \0 to \255. Initially, we have the following prices:

A -> 10, B -> 10, C -> 10

If the code of the first answer is BAAA, then is has a score of 40 (computed by taking the previous character prices into account) and the prices change to

A -> 13, B -> 11, C -> 9

If the next answer is CC, it has a score of 18 and the prices are updated to

A -> 12, B -> 10, C -> 11

The Task

Your objective is to write a program or function which calculates the score of a given piece of code in dependence of a list of previous answers which all influence the initial prices in the way described above.

The goal is to do so while minimizing the submission's score itself in the context of this challenge, that is your submission should be able to calculate its own score by taking a list of all previous submissions and its own source code as input.

The answer with the lowest score in each language wins.

Rules

• You may take a list of strings and a string as input, or require that the string to be scored is the first/last element of the list, or any other reasonable input format.
• You may not answer twice in a row.
• If an answer in language X has already been posted, you may only post another answer in language X if your submission achieves a lower score than the previous answer and the code is not identical.
• For this challenge only major releases of languages are considered their own language (e.g. Java 7 vs. Java 8). If there already is an answer in version A of a language and you have an answer in version B of the language and are in doubt whether version B is different enough from version A to be treated as different language, make sure that your code is not valid in version A.

Answer Format

To avoid having to copy all previous answers in order to calculate your submission's score, the chain will maintain a score calculator on TIO. Click on the link to the calculator in the previous answer and enter your code into the input field to calculate its score. Then add your code as a command-line argument, generate a new link and include it in your answer for the next submission.

If you wrote answer number 42 in Haskell with a score of 100, please format it as

42. Haskell, score 100

 <code>

TIO-Link, explanation, ...

Score calculator for next answer

Test Cases

These test cases are in the format list of strings, string to score -> result.

[], "BAAA" -> 40
["BAAA"], "CC" -> 18
["abc"], "abc" -> 33
["ab12", "aa22", "31a"], "ac23" -> 42
["a","b","c","d","e","f","g","h","i","j"], "123" -> 3

---

Meta

• Any idea what could be a good initial price? I picked the number 10 rather arbitrarily.
• Letting the cost of unused characters decrease until 0 might lead to score 0 answers. Do you think this is a problem and the minimum cost should be 1? Minimum changed to 1.
• I'm unsure what range of characters is a sensible choice. Limiting answers to printable ASCII plus white space would make things easier but also exclude a lot of languages. Another possibility would be to allow the whole byte range from \0 to \255. Then also golfing languages could participate, albeit to score them they would need to be converted to their byte form which usually contains a lot of unprintable characters. The score calculator is able to handle unprintables, but I don't know how to insert them into the text fields on TIO. All bytes from \0 to '\255' are allowed.
• Is the winning criterion suitable for answer chaining?
• A leader board snippet would be nice, but I don't know how to modify the existing ones. If someone could provide such a snippet, I would be very grateful.
• Relevant tags?

Answer 5

Tower Builder king-of-the-hill

The king is coming to visit! Your city is competing with another neighboring city to attract his attention.

Each player owns their own tower within a city full of other players. Each turn you place 1 blocks on your tower or another tower in your city.

After 100 turns, the king will only visit the city with the highest tower. If he visits your city, then you will gain points equal to the number of blocks in your personal tower. In the case of a tie, neither city is visited.

Games include all players, and each game will randomly arrange players into cities. Your score is the total score across all games.

• Player identifiers are randomly generated at the start of the tournament, but are consistent from game to game.
• In addition, contrary to past KoTHs: I allow saving state from game to game (but not between tournaments)
• You will always have complete information, including:
  • The size of everybody's towers (including the other city)
  • The actions players have taken
  • The current score of all players

Answer 6

Chess ASCII Art, Knight

In honor of the world chess championship, in the shortest possible program, output the following ASCII art piece

      ,....,
   ,::::::<
  ,::/^\"``.
 ,::/, `   e`.
,::; |        '.
,::|  \___,-.  c)
;::|     \   '-'
;::|      \
;::|   _.=`\
`;:|.=` _.=`\
  '|_.=`   __\
   `\_..==`` /
    .'.___.-'.
   /          \
  ('--......--')
  /'--......--'\
   "--......--"

This is a code-golf challenge

Answer 7

Is this checkmate?

Input

A chess position in FEN format. You can assume the input is a valid chess position.

Output

Two distinct consistent outputs for checkmate or not.

Examples

8/8/8/8/8/5BKN/8/7k b - - 93 47
Mate

code-golf chess

Answer 8

Lexicographically earliest valid UTF-8 byte sequence permutation

There are currently 1,114,112 possible Unicode characters (code points). Each character has a unique valid byte sequence in the UTF-8 encoding. Different characters have different length encodings:

• ASCII characters have a 1-byte encoding 00-7F.
• The next 1920 characters have a 2-byte encoding C2 80-DF BF.
• The rest of the BMP has a 3-byte encoding E0 A0 80-ED 9F BF and EE 80 80-EF BF BF.
• The other planes have a 4-byte encoding F0 90 80 80-F4 8F BF BF.

It's possible for two strings (specific non-normalised sequences of Unicode code points) of Unicode to have byte sequences that are permutations of each other in a number of ways:

• One string could simply be a permutation of the other at the Unicode level, e.g. ab (61 62) and ba (62 61).
• UTF-8 continuation bytes could be switched between two characters, e.g. ¡â (C2 A1 C3 A2) and ¢á (C2 A2 C3 A1).
• UTF-8 continuation bytes could be switched within a character, e.g. ᴵ (E1 B4 B5) and ᵴ (E1 B5 B4).

For this challenge I would like you to write a program or function that finds the string whose UTF-8 byte sequence is lexicographically earliest of all such sequences that are permutations of the UTF-8 byte sequence of a given Unicode string.

For example, if your input is ᵴ¢ába (E1 B5 B4 C2 A2 C3 A1 62 61) your output would be ab¡âᴵ (61 62 C2 A1 C3 A2 E1 B4 B5).

Note however that some byte sequences are not valid UTF-8 (e.g. E0 80 A0 which is an overlong encoding for a space) so you need to take care to avoid these.

It would be helpful if your "Try It Online" or similar link includes a footer that helps demonstrate the correctness of your output, where this is not obvious from the I/O format or code.

This is code-golf, so the shortest program or function that breaks no standard loopholes wins!

Answer 9

Compose Fill In The Blanks

Answer 10

Move arrows along a contour

Posted here

ascii codegolf

Answer 11

Posted here

Answer 12

Cliquish Program

Challenge: Write a program that accepts a character (or byte, see additional information) as input. Then:

1. If the character is contained within the source code, output a different character also in your source code.
2. If the character is not contained within the source code, output a different character also not in your source code.

This is a code-golf, so the shortest program (in bytes) wins.

Additional Information

• Your program must consist of at least 2 distinct characters.
• Your program must have at least 2 possible outputs.
• Your program does not have to be deterministic; it may output a character at random (with any distribution), so long as it conforms to the above criteria.
• Your program may optionally take a byte as input instead of characters. If you do, the code page the input is written in must contain at least each distinct byte in the source code, as well as at least two different bytes not in the source code.
• You may take input and give output in any reasonable way. For example, you may take input as a function parameter, a command-line argument, a line from STDIN, a triple-nested array containing a single character, etc. You could output via return value, STDOUT, exit code (if applicable), fax output, etc. The input and output formats must be consistent, however.
• Your output can only consist of the required character, optionally followed by one trailing newline. Prompt information (such as ans =) is exempt from this rule; such unpreventable output is acceptable.

Answer 13

Implement Brainfuck Algorithms

code-golfstringbrainfuck

In order to make algorithms written in brainfuck more understandable, you can write them in a more abstract notation, where you give a given cell a name, and instead of lots of unreadable < and > instructions to move the pointer to a specific, you just write down the name of the cell. Let us see an example:

This algorithm doubles the value in cell x, and saves the result again in x. It needs an additional temporary cells t

t[-]          clear temporary variable
x[t+x-]       move the value from x to t
t[x++t-]      move twice as many units from t back to x

Now lets see what this would look like, if x was the cell with index 0, and t was the cell with index 2, assuming the poninter is in position 0 when the algorithm starts:

>>[-] 
<<[>>+<<-]  
>>[<<++>>-]

Challenge

Given a string with a valid (see below) brainfuck algorithm, a list of strings containing the cell names and a list of integers containing the indices of each of the cell of the previous list, your program/function has to return an implementation of this algorithm in brainfuck.

Details

• The pointer is assumed to be on a cell with index 0 when the implementation is executed.
• The two given lists can also be in a different reasonable format e.g. [cell1,index1,cell2,index2,...] or [[cell1,index1],[cell2,index2],... or as arguments of a function with a variable number of arguments etc.
• You can assume that in the given string representing the algorithm, there are only brainfuck instructions as well as cell names, but no other symbols (no line breaks, no spaces)
• The cell names consist of lower- and uppercase characters A-Z and a-z as well as digits 0-9
• The cell names in the string are always separated by at least one BF instruction symbol.
• You can assume that the pointer is the same index whenever it enters a loop as it exits the same loop.

Examples

x=y:

String (remove line breaks):
  temp0[-]
  x[-]
  y[x+temp0+y-]
  temp0[y+temp0-]
List of variable names: [temp0,x,y]
List of indices:        [    2,0,1]
Output (remove line breaks):
  >>[-]
  <<[-]
  >[<+>>+<-]
  >>[<+>-]

x=x*x

String (
  temp0[-]
  temp1[-]
  temp2[-]
  x[temp2+temp1+x-]
  temp1[
    temp2[x+temp0+temp2-]
    temp0[temp2+temp0-]
    temp1-
  ]
List of variable names: [x,temp0,temp1,temp2]
List of indices:        [0,    1,    2,    3]
Output (remove line breaks):
  >[-]
  >[-]
  >[-]
  <<<[>>>+<+<<-]
   >>[
    >[<<+>+>>-]
    <<[>>+<<-]
    >-
  ]

(More to be added)

Answer 14

ASCII Maze Unrendering 3000

mazeascii-artcode-golf

Posted

Answer 15

Question link

Answer 16

Almost Illegal Strings

Posted.

Answer 17

Speed of Lobsters

Answer 18

Print random integers until 0

Answer 19

Remove Nth occurrences

Answer 20

To raise \$ e \$ to the power of a matrix code-golf math matrix

Posted

---

Meta

• Is this clear enough?
• Is this a duplicate?
• Any other feedback?

Answer 21

Non-quining infinite printer

Seems like the title could be better but I'm not sure what to do instead

code-golfquinestring

I have heard that a monkey typing random keys on a typewriter, given infinite time, will eventually type out the entire works of Shakespeare, and in fact type out every possible string of characters of any length. This sounds to me like the basis for a profitable business venture in publishing. Unfortunately, however, as a result of previous failed business ventures, I am legally barred from possessing either monkeys or typewriters, so I'll instead need a program. I want this program to provably generate every possible string of characters, assuming infinite time and memory. Repetition is fine, as is overlap, as long as every possible string appears somewhere in the output. There's a catch, though. I imagine once my business gets off the ground and people realize the potential profits, they might want to get their hands on my program. The trouble is that since I'm outputting every possible string of text, in theory I'll eventually end up outputting the program itself, leaving it open to be stolen. To prevent this, I want the program never to output its own source code. It should still output every other possible string, just not itself (or, obviously, any strings which it is a substring of). Because my funds are currently very tight, I can't afford to pay for more bytes than are necessary, so I'm seeking the shortest possible program that does the job (This is a code-golf challenge, shortest answer in bytes wins). Is it communicated well enough what this challenge is asking for? Should I add a TL;DR and/or a more technical explanation of what's being looked for?

Additional notes:

• I've had enough run-ins with the law in previous ventures, I'd like this one to go smoothly. So no abusing loopholes in the program, please.
• Given that this program is my financial plan for the next infinity years, I'd like some reassurance that it actually does what it's supposed to. Please provide at least a brief explanation of why your code works, since it can't exactly be tested.
• Any character encoding is fine, please specify though. The exception is that your source code must be printable in the encoding you use. Is this a reasonable way to handle this that is fair to all languages?
• No reading your own source, because that makes quine-related holes uncool, and uncoolness does not fit with my businesses' brand persona.

Answer 22

Who Is Kevin Bacon?

Answer 23

Sort every dimension

Answer 24

Output a random unary string

Answer 25

Building spikes

Answer 26

Sort numbers in a ragged list

Answer 27

King of the Holster (EXITING SANDBOX TOMORRROW)

I realized there hadn't been a King of the Hill in forever, so I wanted to create one.

Before the Game

You will be given 10 points to distribute between HP, Dexterity, Armor, and Speed. You may distribute up to 10 points between these categories (integer amounts only). You do not have to put a point in each category.

• Your HP will equal 10 plus the number of points you put in HP.
• Your Dexterity (chance of dodging a hit) is equal to 0.04 times the number of points you put in Dexterity. For example, if you put 8 points in Dex, you would have a .32 chance of dodging a hit.
• Your Armor (chance of taking 1 less damage from a hit) is equal to .1 times the number of points you put into Armor.
• Your Speed is simply equal to the number of points you put in Speed.
• You always start with 2 ammo.

Gameplay

Agents will be ordered based on their speed, with ties being broken at random before the game begins. On their turn, each agent will be given their HP, all of their stats (max HP, Dexterity, Armor, and Speed), how much ammo they have, who they attacked most recently, and who attacked them most recently.

On each agent's turn, there are three possible moves:

• Heal: If not at maximum HP, gain 1 HP.
• Reload: Gain 2 ammo.
• Shoot: Choose another agent. They get a random real from 0 to 1. If that number is less than their dexterity, they dodge and take 0 damage. Otherwise, they take a random integer amount of damage from 1 to 4, then they generate another random real from 0 to 1. If that number is less than their armor, they take 1 less damage.

TLDR: Shooting does 0 damage if they dodge, 0 to 3 if they get armor but no dodge, 1 to 4 if none.

Once an agent's HP is less than 0, it is out and can no longer take actions. Last agent surviving wins the round.

Scoring

Each round, if there were X agents, your agent receives X points for each agent below it. Therefore, in a 10 player game, the top agent would get 9 points, the second would get 8, and so on. I can currently run 5000 3-player modes in 10 or so seconds (probably much faster if I removed some of the printing for debugging), so as long as nobody's agent takes too long to run, I should be able to run thousands of score tests.

I/O

Currently, submissions will create a class which extends PlayerClass. It will create a new class constructor that takes no inputs, which will call super() with the points it wants in each category. Additionally, you will redefine the makeMove function, which takes no inputs and calls move() with whatever arguments are required.

Rules

Submissions in Java only. As long as the submission is simple enough, I might be able to translate from pseudocode/some other language to Java though.

No calling any methods of other entities using shenanigans. The biggest problem here is takeDamage(), which has to be public so it can be called when someone is shot. Other than that, there shouldn't be any public functions other than turn-order functions, which are probably fine to access.

No redefining any functions/variables of PlayerClass besides makeMove().

The subclass constructor must be of the form super(x,y,z,a); and cannot overwrite the requirements in the PlayerClass constructor.

You may define other methods within your class IF they are only called as part of generating your stats or deciding who to shoot and they follow the rules outlined above.

Don't make your code take forever. This KOTH is pretty lightweight, so there shouldn't be a need for complex algorithms.

---

The controller and four basic test agents can be found here: https://github.com/romanpwolfram/GunfightKoTH/tree/main

Challenge name by tjjfvi.

king-of-the-hill

Answer 28

Convert Alpha-3 to Alpha-2

Answer 29

Shortest restricted superstring

Answer 30

ITEXTIN - Is This an EXTended Initialism?

decision-problem Please write a program or function that, when given a list of words and proposed extended initialism, outputs whether it is valid.

Rules:

• The list will contain at least two words.
• The extended initialism will contain at least three letters.
• Each word in the phrase contributes a prefix to the extended initialism.
• This prefix must not be the whole word.
• In the case of the first and last words, the prefix must not be empty.
• The extended initialism is the concatenation of these prefixes.
• Inputs are alphabetic only, your choice of upper or lower case.
• Separators, if you want them, are any symbol or white space.

Examples (truthy):

laser=light amplification by the stimulated emission of radiation
radar=radio detection and ranging

Examples (falsy):

labyser=light amplification by the stimulated emission of radiation
radar=light amplification by the stimulated emission of radiation
dear=radio detection and ranging

This is code-golf, so the shortest program or function that breaks no standard loopholes wins!