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.

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".

Answer 1

Feedback Wanted

• Is this too vague? should I change it to something like "create a quine with the fewest unique bytes", or perhaps adapt another existing challenge that might otherwise use lots of repeated bytes?
• Maybe the idea is just too boring on its own and I should create a new proper challenge based around it?
• Should I change the scoring system (votes - unique_bytes) - should it be divided instead, or use a more complex formula?

Introduction

This is code-golf, but not as you know it. Instead of every byte, This is sort-of also a restricted-source question.

Challenge

Write an interesting program that uses the fewest unique bytes. This is not really about what the program does, but what you can do with a limited set of characters.

Rules

• Your program must run on Try It Online
• Programming languages with only a few permissible bytes anyway like Brainfuck's +-.,[]<>, are allowed, but officially considered boring

Apart from this, you can write anything.

Scoring

• Hybrid of popularity-contest and "fewest-unique-bytes". Score is calculated as votes - unique_bytes
• Unique bytes is based on bytes, not characters or whatever. You can calculate unique bytes using this Python snippet: len(set(b"your code here"))

Answer 2

Solving P=NP!

Today, we are going to solve P=NP, kinda...

Input

A guaranteed prime positive integer, P.

Output

The smallest composite number (NonPrime,NP) which sum of digits equals P.

Examples

Input (P)    Output (NP)      Why? (for reference)
  2              20          2+0=2 and 11 is prime
  3              12                 1+2=3
  5              14                 1+4=5
  7              16                 1+6=7
  11             38          3+8=11 and 29 is prime
  13             49                 4+9=13
  17             98          9+8=17 and 89 is prime

Check OEIS A073868 for more results.

Challenge

Write a function or program that, given a positive prime number P as input, calculates NP, the smallest composite number which sum of digits equals P.

• Range of input: any integer prime number greater than 1, up to the limit of the chosen language.
• Range of output: also according to the limits of the chosen language.
• Means of input/output: free to choose.

Winning condition

This is a code-golf challenge. The shortest code wins!

Tags

code-golfprimesnumbersequence

Meta

I have searched if this was already posted, but with no success.

Answer 3

English Grammar Checker

regular-expressionnatural-languagegrammars

Being tired of checking English grammar, I decided to write an English grammar regular expression.

Notations

1. All capital letters denote an expression.
2. Quoted strings (like "a") and lower-case letters denotes literals.
3. AB means concatenating expressions / literals A and B together.
4. (...) groups the expression inside the parentheses, as a whole expression.
5. A* means repeating the expression A zero or more times.
6. A? means the expression A is optional here.
7. A|B means either A or B can be placed here.
8. A=B means all expression A should be replaced by B.

Grammatical Rules

Parts of Speech

For simplicity, all parts of speech are substituted using symbols.

Symbol	Part of Speech
a	article
b	verb
j	adjective
m	numeral
n	noun
r	pronoun
v	adverb

Rules

There's a whole bunch of rules in English grammar. For simplicity, I only chose a tip of the iceberg. Your RegEx should only match all valid S's.

1. S=N+V
2. N=((a|m)?j*n(pN)?)|r
3. V=b((pN)*|N)?v?

Examples

These should be matched	Real-life example
anb	The man runs
rbpajjnv	He dives into the deep blue sea quickly
anpanbpr	The wave on the sea came towards me
mnpambv	Two friends of the man walks slowly
anpmjjnbajjnv	The robot of two tall thin girls greets the young handsome man repeatedly

These shouldn't be matched	Real-life "wrong" sentences example
nn	Man child
nabr	Student a told me
arbv	The you laughed happily
anbvv	The woman sang slowly beautifully
rbvj	He is very funny

Notice that the last example is a valid English sentence, but it doesn't match our simplified rules. You shouldn't match them.

Tips

You can assume that there's no whitespaces and line feeds in the input.

You can assume that you only need to match 1 input per time.

You can use any RegEx dialects no newer than this challenge.

Scoring

Your score is the bytes in your RegEx. Flags are not counted.

The least score wins!

Answer 4

Given a positive even integer \$n\$, generate a random Brainfuck snippet of length \$n\$, containing only +-<>, that do no modify to the tape or tapehead.

To avoid random generation and try again or fallback into a trivial nop for invalid nops, your solution should run in polynomial time, and the ratio of possibility returning any two nops should be below polynomial.

Answer 5

Solve any NPC problem. Shortest code win.

Sandbox Notes

• Will every submission tend to single NPC problem?
• How many builtins are known to solve this in Mathematica?
• Do 0-byte solution exist?

Answer 6

Compress La Campanella.

Notice that music theory may give you more rules than general compress give, but I don't know music theory that much, so I won't post this

Answer 7

Self-Obfuscator Program

According to Wikipedia,

obfuscation is the deliberate act of creating source or machine code that is difficult for humans to understand.

In this challenge, you need to create a program that'll be able to obfuscate itself and produce a program with the same functionality, using the shortest amount of bytes required.

Rules

• Standard loopholes are prohibited.
• The output must always be consistent for each input. If you take the original code (iteration 0) and run it through itself 10 times to get a very long obfuscated code (iteration 10), running the initial code through it should give a code identical to iteration 1 code.
• The output must be at least twice as long from the input for each iteration.

Obfuscated, not verbose

• The obfuscation process must make the code longer, but it mustn't add any comments, no-op or no-effect statements, or any statements or expressions that don't directly affect the output code.
• The output should have minimal resemblance to the input. No sequence of 5 bytes should repeat in the output.
• The code must be able to obfuscate itself, obfuscations of itself from further ahead iterations and code from earlier iterations. It's not required to be able to obfuscate anything else.

Answer 8

The number of alphabets in 3 seconds

fastest-code

In 3 seconds, output as many alphabets as possible. The output may be separated by consistent character.

An alphabet here is this:

abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ

Meta

• Is this clear?
• I'm not really sure about the tagging.

Answer 9

TDG - Test Driven Golf

popularity-contest

Our company requires unit testing before code can be deployed to production. Unfortunately, my code is written in esoteric programming languages, none of which have test runners.

Please help me get to production!

Challenge

Write a test runner for a programming language (here after called Language X) that takes Language X source code and Language X test cases then outputs the results of running the test cases.

NOTE: The language used to write the test runner does not necessarily have to be Language X.

Specification

Input

The runner should take in:

• Code written in Language X
• Test cases written in Language X

Output

The runner should produce:

• At least a list of test cases. For each test case, include:
  • The test case name
  • A Truthy value if the code executes without errors and no assertions failed
  • A Falsey value if the code errors or an assertion failed

Test Runner

• The test runner can be written in any language. The only constraint is that the source and test code language be the same
• Each test runner must at least provide a helper/utility/function to assert that a value is truthy
  • Assert.True(false) => Fails test
  • assertTrue(1 == 3) => Fails test
  • is_truthy 1 => Doesn't fail
  • [[ "a" = "a" ]] => Doesn't fail

Test Cases

• Each test case must have a name/be name-able
  • it("does stuff", _ => ...) => it does stuff
  • it_does_stuff = _ => ... => it_does_stuff
  • func ItDoesStuff() {...} => ItDoesStuff
• A code block of language X code

Submissions

For consistency, here are some recommendations:

• Title should be: # Language X runner written in Language Y
  • Where Language X is the source and test code language
  • And Language Y is the language the runner is written in
• Runner code in a ## Runner section
• Example input source code in a ## Example Source section
• Example input test code in a ## Example Tests section
• Example output in a ## Example Output section

Sandbox Questions

• Is this challenge too board?
• Is this challenge too big?
• I've created some basic test runners in a single file before and with some elbow grease, I think you could say small (submit-able on CGCC) and add a few nice things
• Does popularity-contest fit here?
• Is there room for creativity?
  • The testing syntax and features for the test cases are left up to the implementation
    • How golf-able the test syntax is
    • How the code and test cases interact
    • What asserts/helpers are provided
    • Syntax for skipping test cases
    • Syntax for beforeEach/afterEach
    • Harder features like parameterized tests and fixtures are possible
  • Similarly, the features for the test runner are left pretty open ended
    • TAP output
    • JUnit output
    • Test isolation and parallelization
    • Harder features like specific failure messages and code coverage aren't impossible

Answer 10

Alternate brackets

Given a matched string containing only ()[]{}, apply the following:

• If [] is next to () or {}, replace the () or {} with [].
• If a () follows [] or {}, remove the ().

Test cases

()[]{} => [][][]
{}(){} => (){}

Answer 11

Task

Make a program that finds the first IP address that responds to pings after a certain IP address.

Requirements

Your program should take an IP address as a string in the form xx.xx.xx.xx. It should find the first IP greater than the input (incrementing least significant byte first) that responds to pings, and output it in the form xx.xx.xx.xx.

Scoring

This is code-golf, so shortest answer in bytes wins.

Answer 12

Write a program on any language that accepts some input and give some different output. The challenge is that the text of the program must form a square: all rows must be the same length and the number of rows must equal the number of columns (ie length of rows). Adding extra spaces, dead code, or comments to pad lines is not allowed.

This is Code Golf so the one with the shortest functioning program (ie smallest square) wins!

Answer 13

Self-Debugger.

Suddenly, someone comes and deletes a character from the program. From analyzing the output and error messages (if any), you quickly know which character was deleted.

Your job is to create a function that does this. For every character deletion, you will get one point if feeding the output and error message(s) to the undamaged function does not give the correct deleted character. You attempt to minimize the score of your program. Your program must have a function, i.e. if must not be empty.

Default loopholes forbidden, as always.

Example program:

lambda a,aa:'a'

Score: the program is not correct when we take away a character that is not a. Thus, the score is 9. (We intend to minimize this score.)

coding-challenges

Answer 14

🤖 Robotics competition

You're entering a robotics competition! There are 3 types of parts for you to choose for your robot: wheels, legs and sensors. A robot:

• can have up to 8 parts in total
• can only have 4 legs
• must have at least 2 parts
• must have at least one leg or one wheel

You can't decide what robot to build, so you'll just make all of the possible ones. How many robots will you build?

The challenge

Write a program which calculates the number of possible robots (the answer is 134). Shortest program wins.

The output of your program can be its return code. The program needn't take any input (undefined behaviour if input is provided).

Bonus swag points for a point-free solution in APL 😉

Example

A non-competitive python example:

from itertools import chain, combinations_with_replacement

options = list(filter(
    lambda option: \
        len(option) >= 2 and \
        option.count('leg') <= 4 and \
        (option.count('leg') + option.count('wheel') > 0),
    chain(*(combinations_with_replacement(('leg', 'wheel', 'sensor'), j) for j in range(9)))
))

for option in options:
    print(option)
print("Number of valid options: {}".format(len(options)))

META

• Is the question original enough, or has there been any challenges like this
• Is the python example a useful thing to include?

Answer 15

ABACABA pattern without recursion

ABACABA pattern on Wikipedia

Taking a number n as input, generate the ABACABA pattern with n symbols as stated in the above page, without using any form of recursion in your code. You can use any output method; characters, a list of numbers, an image, whatever is possible.

If taking input is not possible in your programming language, output the pattern forever. E.g.: ABACABADABACABAE...

Test cases:

input => output

1 => A / 1
2 => ABA / 1, 2, 1
3 => ABACABA / 1, 2, 1, 3, 1, 2, 1
4 => ABACABADABACABA / 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1
5 => ABACABADABACABAEABACABADABACABA / 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1, 5, 1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1
```

Answer 16

Detect if a variable is declared

Create an expression which detects if a variable (named whatever you wish) has been declared yet. For languages that set undeclared variables to a type that can not be differentiated from a declared variable set to that type (e.g. nil in Lua), just detecting that type is enough. If the variable exists, the expression should return a truthy value, and if it doesn't it should return a falsy value. It should not output anything.

For example, the following expression in D detects if a variable named x has been declared in the current scope or not:

__traits(compiles, x)

PS: this challenge definitely wouldn't work for stack-based or assembly languages, and I'm also not sure if marking this as code-golf or popularity-contest would be better.

Answer 17

PHPFuck Golf - Hello World

Like this

PHPFuck is an esoteric language in which any PHP statement can be accurately reproduced into another valid PHP program that uses only the 5 characters (^.9).

The PHPFuck converter, when given an input of echo "Hello World!", produces a block of code that is 74,450 characters long. Because the program used a lot of automatic conversions to create that block, I believe that the code can be made a lot shorter using manual optimizations.

Your task is to build a PHP program that performs the task echo "Hello World!", using only the characters (^.9). The shortest code to do so wins.

Answer 18

Polishing off a Sudoku

Given a set of 8 numbers as input, output the missing one.

Examples

12346789 -> 5

94351726 -> 8

Answer 19

Print the input times infinity

Make a program/function that prints the input of the function infinite times, separated be a line break. Do note that the output must be to stdout.
tags: code-golf

Answer 20

That is disproportionate!

You want to overwhelm your nasty boss with an error message so large that they quit their job. But your boss will fire you instead if it's too long.

---

Challenge

In this challenge, you have to write code that is more than 0 bytes long that produces the longest error message possible.

Scoring

Answers will be scored using this formula: $$\frac{\text{Error message length in bytes}}{\text{Programme length in bytes}}$$

Other

All answers must include the answer score, source code and error message.

---

code-challengeerror-message

---

Meta

• Is this a duplicate?
• Any other appropriate tags?
• Anything else?

Answer 21

KCMCK

Print this ASCII art:

  +--------------  +-+                   +-+   +--------------  |
 ++                | |                   | |  ++                |
 |                 |  \                  / |  |                 |
 |                 |   \                /  |  |                 |
 |                 |    \              /   |  |                 |
 |                 |     \            /    |  |                 |
 |                 |      \          /     |  |                 |
 |                 |       \        /      |  |                 |
 |                 |        \      /       |  |                 |
 |                 |         \    /        |  |                 |
 ++                |          \  /         |  ++                |
  +--------------  |           \/          |   +--------------  |
________________________________________________________________|
________________________________________________________________|

Shortest code in characters wins!

• Any leading whitespace must be the same on every line.
• No restrictions on trailing whitespace.

Answer 22

Be a cat

I have not found a single challenge that asks for a plain cat programme. The closest I have found requires you to print cat goes meow when the input is cat.

---

In this challenge, you must read everything from STDIN, or an acceptable alternative, and print the exact text to STDOUT, or an acceptable alternative, with only the leading and trailing whitespace in the input.

---

Meta

• Have I been so silly that I missed a duplicate?

Answer 23

Type annotation

Given a function definition and a list of types, both valid in your language, output the function annotated with those types. Shortest code wins, since this is code-golf.

Meta

• Is it a duplicate?
• How should I include languages without type annotation support?
• Does it need to be explained better?
• Anything else?

Answer 24

Execute... yourself!

Almost a duplicate, but only requires you to compile a subset, and is closed.

---

You work at a compiler factory, making compilers tailored to your customers.

---

Challenge

In a programming language of your choice, write a program that executes code in the chosen language. Snippets are allowed, but you may not hardcode the input.

This is code-golf, so shortest code wins!

---

Meta

• To deal with languages like No, should I change it to a popularity-contest, or disallow languages like that completely?
• Is it clear enough?
• Are there any unclosed challenges this duplicates?
• Anything else?

---

code-golfcompiler

Answer 25

Code-challenge: Guess my number

The challenge

You have a number from 1 to 10 in mind, and your program should ask questions to find out which number. These questions can be any questions, the program only has to find out the number as fast as possible.

Your program should ask a question, such as "Is the number a prime?", and the user must answer either y or n (yes or no). Ask questions until you know the number.

The scoring

To calculate the score, you need to take the sum of the question count for each number. For example, if you need 1 question to find the number 1, 2 questions to find the number 2, and so on, the score is 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10, so the score is 55.

Important note: the question count for a specific number must always be the same. For example, if you need 4 questions to find out the number 10, then you have to ask always 4 questions to find out the number 10, otherwise it is impossible to calculate the score.

Answer 26

Popularity Contest: Implementation of a Hash Table

Create a class in some OOP language for a hash table that supports getting, setting, and removing values. You can't use the built in hash table/dictionary/map implementation. Highest votes in one week wins.

A key is any valid string. A value is any valid string, number, or boolean.

Example functionality:

hash.set("key","value");
hash.get("key"); // returns "value"
hash.set("key", 1234);
hash.get("key"); // returns 1234
hash.set("key2",hash.get("key"));
hash.get("key2"); // returns 1234
hash.delete("key");
hash.get("key"); // returns null/undefined/none/etc. or throws an error
hash.get("key2"); // still returns 1234

Definition of a hash table (from Wikipedia):

In computing, a hash table (also hash map) is a data structure used to implement an associative array, a structure that can map keys to values. A hash table uses a hash function to compute an index into an array of buckets or slots, from which the correct value can be found.

The hash table cannot be simply an array that is searched in linear time. It must be an actual hash table that uses a hash function to map the keys to the value.

Answer 27

Bovine Ignorance

I'm curious about code which still works after being mangled by figlet, toilet, cowsay et al, but I'm not sure whether this in any way sane.

What I'm toying with is a challenge in which a participant may submit any program in any language. It should be possible to use this program's source code as input to cowsay or whatever, and the result should be another valid program in any language, which still does a similar thing. For instance, the following bf program prints Hello world! with no newline:

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

Running cat ./prog.bf | cowsay -e .. -T $'>.' yields the following output:

 _________________________________________
/ +++++ +++++ [ > +++++ ++ > +++++ +++++  \
| > +++ > + <<<< - ] > ++ . > + . +++++   |
| ++ . . +++ . > ++ . << +++++ +++++      |
| +++++ . > . +++ . ----- - . ----- --- . |
| > + .                                   |
| +++++++++++++++++++++++++++++++++++++++ |
\ ++                                      /
 -----------------------------------------
        \   ^__^
         \  (..)\_______
            (__)\       )\/\
             >. ||----w |
                ||     ||

Which is itself a valid bf program which prints Hello world!!!, followed by a newline.

The problem with using bf here is that it ignores most of the cow, making this a bit too easy. The problem with using any other language is that it doesn't ignore most of the cow, making this far too difficult. Is there a sensible middle ground I could pick for this? I don't think it's impossible, I'm fairly sure you can exploit cowsay's behavior on one-liners to produce valid svgs, but I'm not sure how best to pose this challenge. Any ideas?

Answer 28

99 Bottles of Errors

While there are already many versions of "print 99 Bottles of Beer," I thought another one wouldn't hurt.

---

The challenge is fairly simple: print the lyrics to 99 bottles of Beer to STDERR. I don't care how you do it, so long as the entire lyrics show up. An entire program is required, so the following Java program would be invalid (even if it did do the correct thing):

System.out.println("99 Bottles of Beer on the Wall, take one down and pass it around...");

The scoring:

• This challenge is code-golf, so shortest code by byte count wins.
• If necessary, assume UTF-8 is the character encoding used.

The rules

• All the code must be in one file.
• Any language is allowed.
• Reading input, whether it is from STDIN, a file, or the web, is not allowed.

Answer 29

Create an Identicon Generator

The challenge is to create an identicon generator. The identicons must be randomly generated, so we get a new identicon for each key the program receives. You can input a key using std-in or you can use your language's random number generator for the key.

In order to make your identicon look reasonably nice, it must generate a picture, then rotate that picture around the bottom right corner, the way this mockup shows:

The output must be to a PNG file. Shortest code wins.

Answer 30

Shortest Program that May or May not Terminate:

Write a program such that whether or not it terminates depends on the answer to an unsolved question in Computer Science or Mathematics. For example, your program might test the Goldbach conjecture for every N and quit if a counterexample is found, or hunt for odd perfect numbers. Please include an explanation of why your program may or may not terminate!

Note: assume infinite memory and stack size, because otherwise they all terminate. Your program must be self contained, take no input, and only use standard libraries. This is Codegolf, so shortest code wins!