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

Popularly print the input

popularity-contest

Goal

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

Specifications

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

Winner

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

Answer 2

Make a Login Screen

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

This is Code-Golf, Shortest answer wins.

Standard loopholes are forbidden.

Answer 3

Of numbers of letters

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

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

Best of Luck

Answer 4

No strings code bowling

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

• Contain any strings, or quotation marks/apostrophes/backticks
• Contain the same alphanumeric byte more than twice
• Conatin the same non alphanumeric byte more than three times

Answer 5

[Posted, but reference kept]

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

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

Sample input:

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

Sample output: 0 2

Sample input:

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

Sample output: 0 1 2 0 1 2

Sample input:

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

Sample output: (empty)

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

You may check your answer here

Answer 6

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

Static visualization of bubble sort and a gif explanation.

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

---

The rules

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

• The function must print each step of the sort.

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

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

• It's code-golf so the shortest code wins!

---

Test cases

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

---

Optional

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

---

Note

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

^{This is not a duplicate of Bubble sorting in progress.}

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

code-golfbubblesorting

Answer 7

Once, I thought of this. Rules:

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

2: One thing per round.

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

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

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

6: One may code in anything they wish.

7: Have fun!

Round 1: Squidward's head!

Answer 8

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

---

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

12

123

1234

12345

with the ability to handle up to the integer

123456789

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

21

321

4321

54321

987654321

Task

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

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

Test cases

Valid list items

12 -> [21] // done

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

Invalid list items

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

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

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

Winning criteria

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

Examples

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

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

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

Answer 9

All numeric substrings

code-golf

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

Input:

A string.

Output:

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

I/O

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

Test cases

(input → one ordering of the correct output)

• 1212 → [1212, 121, 212, 12, 21, 1, 2]
• 123٤٥6 ‪→ [1, 2, 3, ٤,‪ ٥, 6, 12, 23, 3٤,‪ ٤٥,‪ ٥6,‪ 123, 23٤,‪ 3٤٥,‪ ٤٥6,‪ 123٤,‪ 23٤٥,‪ 3٤٥6,‪ 123٤٥,‪ 23٤٥6,‪ 123٤٥6]‪
• 12t45 → [1, 2, 4, 5, 12, 45]
• abc → []

Answer 10

Fastest prime printer up to 500,000,000 with gapes

---

Write a program that takes no input and prints the first 26,355,867 prime numbers, from 2 to 499,999,993 inclusively. Or in other words, print all the prime numbers smaller the 500,000,000.

The fastest code wins!

Since it will take a long time to print all the numbers, print only every 26355 primes starting with 2 separated by a new line. So the output should look like this:

2
304417
648391
1007681
1376449
1752323
2133689
2520983
2910797
3304633
3702269

The output should not be hardcoded, or there is no fun in it.

The results will be tested on my machine, so please also output in the last line how long it took to run the program and give me some instructions about how to run it locally. I will then share the last line output with you that should contain the time it took to run.

Here is my machine system specs, note that it's Windows.

Answer 11

Mystery Numbers Challenge math

Here are some sample inputs and outputs:

IO

Test 1

Input: 102
Output: 10404 1061208 14002414191924244276669361796022272

Test 2

Input: 10
Output: 100 100000

Test 3

Input: 50
Output: 2500 312500000 312500000

BONUS

If there are two inputs, here are the corresponding inputs and outputs:

Test B1

Input:

50
12

Output: 144 248832 248832

Test B1

Input:

2310
9

Output: 81 729 59049 4782969 31381059609

Notes

If you pass all bonuses too, feel free to third your score. Also add a * to the end.

Answer 12

Your challenge is to write a small compiler/interpreter to a small language. This language can be of any level. Example: brainf*ck or Turing.

Example submission:

languageName : “name” 
GitHub : “https/GitHub.com/Lang”

a language is valid if it contains the folowing systems:

1: varibles of any type
2: a method of declaring and using functions
3: definable parameters
4: a update loop
5: loops
6: classes(optinal)

a compiler/interperater is valid if it can:

1: run/compile code
2: is fast (less than a minute to compile/initialize)
3: give error messages(optional)
4: written in java

The smallest compiler/interpreter wins

please tell me how i can fix this post if you intend on downvoting it in the comments

Answer 13

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

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

no imports are allowed either

An integer will be given in the input

Test cases:

5 -> 25

6 -> 36

10 -> 10

724 -> 524176

Answer 14

Prime strings

Your task is to find the string consisting of all the words in the give input whose lengths are prime numbers

Test cases:

The quick brown fox jumps over the lazy dog.
->
The quick brown fox jumps the

Omicron Effect: Foreign Flights Won't Resume On Dec 15, Decision Later.
->
Omicron Effect: Foreign Flights Won't On Dec 15,

You may assume that only ascii characters are allowed and that uppercase, lower case, punctuation, and spaces are allowed in the input and output

You may assume that the words whose lengths are prime numbers do not include spaces

Answer 15

Outgolf me with the custom scoring

Cops:

You post two codes, a code is that you wanted to do, another is used to size the code.

Rules

• Outgolfing must be 1 bytes or fewer

• Code that sizes solves the decision-problem is Fine

• Standard loopholes apply

Example:

# [Python 3](https://docs.python.org/3/), score 21 

# Code

    print("""s""")

# Sizer

    print(len(input())/2)

Scoring (Cops)

\$s + \lfloor\frac{(m)}3\rfloor\$

Where \$s\$ is the size of actual code and \$m\$ is the size of code used for sizing the code.

The lowest Score of uncracked Cop wins

Robbers

Your task is to find code, If the code size is less than the Cop's code, Then Post an answer That cracks the Cop's answer.

Rules

• Standard loopholes apply

Example:

# [Python 3](https://docs.python.org/3/), [Cracks username Cop](https://codegolf.stackexchange.com/questions), 2 score saved

    print("s")

The Poster with most cracks wins

Meta

• Any feedback?

Answer 16

Python Interpreter

Mimic the python interpreter.
Running python <filename>.py should be the same as running python in the terminal (or python3, python27, and other similar pythons)
It's really hard. Especially complying with the following STDIN test cases.

(SANBDOX - should I add code-golf? What other tags should/shouldn't I add?)

Also, it seems ast is too overpowered, as the main hard part (sys.ps2 compliance) can be fixed by checking for IndentationError: expected an indented block when calling ast.parse. Any ideas?

Test cases

Copy this and test this with your program.
Make sure the output is identical to the interpreter.

Simple code

for i in range(5):
    print(i)
<a blank line>
print(i)
i
_
while False:
    print("Will not be executed")
<a blank line>

When sys.ps1 and sys.ps2...

import sys
sys.ps1 = 'ps1> '
print("sys.ps1!")
sys.ps2 = 'ps2> '
for i in range(1):
    print("sys.ps2!")
<a blank line>
print("end")

Errors

raise ValueError

Handling crashes (this is optional)

def a():
    try:
        a()
    except:
        a()
<a blank line>
a()

Sandbox sanbdox things

Repeated: (SANBDOX - should I add code-golf? What other tags should/shouldn't I add?)

Also, it seems ast is too overpowered, as the main hard part (sys.ps2 compliance) can be fixed by checking for IndentationError: expected an indented block when calling ast.parse. Any ideas?

• Any things that needs to be changed?
• Any unclear bits? Probably a lot...
• Any other things?
• Any reason all my sanbdox questions start with "Any"?
• Any idea whether I should remove the "Any" before every sanBDox thing?
• Any sanbdox template so I don't have to copy from my evolution of trust sanbdox post?
• Any way to stop misspelling sanbdox?

WD

Answer 17

Generate a random string of length 8

The challenge is pretty simple. Generate a random (non-zero chance) string of length 8, using ASCII characters from 33-126 (! to ~). (1-32 and aren't included because they don't show up/may cause interference.)
Remember that this is code-golf, so shortest answer wins!

Rules

• All standard rules apply
• All characters must be in one continuous string, so no line breaks, spaces, etc.

Example code

import random
i=8
j=""
while i!=0:
    j+=(chr(random.randint(33,127)))
    i-=1
print(j)

Try it online!

Tags

code-golf random string

Answer 18

Longest code to output "Hello World"

Rules

1. The program should take no input, and only print Hello!, World? to STDOUT with exact same capitalization and punctuation and in single line. Trailing whitespaces and newlines are allowed.
2. The output should not be in the form of error message
3. The accepted answer will be the 'most points' answer but try to be as creative as possible

Point System

1. +1 for each character of code in your program, eg:print("Hello World") is 20
2. -1 for each repeated character(case sensitive, i.e. 'h' is not same as 'H'), eg:print("Hello World") is 20-1(o)-2(l) = 17

Answer 19

Calculate the day of the week from a given date without using built-in functions that do so. For example C#'s DateTime.DayOfWeek is not allowed. Anything along the lines of DateTime.Year.IsLeapYear or DateTime.Month.TotalDaysInThatMonth (pseudocode) is also disallowed. Anything other built-in functionality for getting the number of days in a month or year is disallowed. You have to build that functionality yourself.

Input: a 1 dimentional array of integers with length 3. The array has the the form {year, month, day}
Output: A string such as "Monday", "Tuesday", etc. Case insensitive.

This is code gold so the shortest answer wins!

Test Cases:

Input	Output
{1000, 3, 31}	"Monday"
{1969, 4, 20}	"Sunday"
{1980, 2, 29}	"Friday"
{1979, 2, 29}	empty string, or null or throws an error. (This date does not exist)

Answer 20

Is it a Homestuck handle?

code-golf string

In the interactive webcomic Homestuck, the in-universe chat clients require users to have chat handles. These handles always consist of two words in camelCase. The heroes in the story almost all have handles where both words start with a DNA base (A, C, T, or G), with one exception.

(Taken from https://mspaintadventures.fandom.com/wiki/Handle)

Your challenge is, given a string (or list of characters), determine if it's one of the heroes' handles -- in other words, if it's in the set {gardenGnostic, gallowsCalibrator, grimAuxiliatrix, ghostyTrickster, ectoBiologist, gutsyGumshoe, golgothasTerror, carcinoGeneticist, cuttlefishCuller, caligulasAquarium, centaursTesticle, arachnidsGrip, arsenicCatnip, apocalypseArisen, adiosToreador, turntechGodhead, terminallyCapricious, twinArmageddons, tentacleTherapist, tipsyGnostalgic, timaeusTestified}. You can output any two distinct values for "yes" and "no".

Standard loopholes are forbidden. The shortest code wins.

Questions

I actually don't know anything about Homestuck, so I probably messed something up in the question.

Answer 21

Do you trust this site?

title is a work in progress

This challenge is simple. Your program must take a URL (which will always exist) as input, download the file, and execute its contents as a program in the language your answer is in. The file will always be a valid program in your language.

Example

Language: Python
Input: https://gist.githubusercontent.com/GingerIndustries/d6f25007b45071e901b2b9057388d8f8/raw/25f838879fdc93f07394afc080eeef0993f55cbe/helloworld.py
Result: Program should print "Hello World!"

Answer 22

Is the UTF-1 string shorter than its UTF-8?

code-golf decision-problem

Backgrounds

• explain utf-1 and utf-8

Problem

Given a Unicode string, output a two distinct truthy or falsey value to represent whether its representation in UTF-1 is shorter than that in UTF-8.

I/O restriction

Input can be list of code point for each letter or string with consistent encoding except UTF-1. Output can be as in decision problem rule.

todo rules

todo test cases

• Falsey for any string with nothing other than c such that U+0000<=c<=U+007F

Answer 23

This is a famous mathematical problem, Named as Bridges of Königsberg

Task

The bridges of Königsberg is a problem in mathematics which states that the path required for crossing each bridge exactly once without using a boat

You have to find out if there is any path which uses each bridges exactly once without using a boat, if the time exceeds 36000 seconds or 10 hours the program should print no path found yet

Rules

Standard rules of fastest-code

Expected Output: Paths possible: [7, 2, 3, 1, 5, 6, 4], [2, 1, 7, 3, 4, 6, 5], etc.

This is fastest-code so the answer with shortest time is accepted, Even if the code will take a many days without a Quantum Computer

Answer 24

Output a googol code-golfnumberkolmogorov-complexity

Your challenge today is to output this exact number:

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

We call this a googol. A googol is 1 followed by a 100 zeroes, or basically just \$10^{100} \$. However most programs wouldn't be able to do a simple print(10**100) because it will take forever to do so. And sometimes it might end up with an OverflowError, so you'll have to be creative.

Input:

None.

Output:

The googol. However, if your language will not be able to store \$ 10^{100} \$, you'll have to find some way of printing it, maybe by string manipulation (the shortest I got was print('1'+'0'*100))

This is code-golf, so shortest answer wins!

Answer 25

Write a proper quine.

Community decided that you're not allowed to claim you're not reading source code but data, and read a stored string.

To be consistent, reading a stored infinite precision number is also not allowed. (should this, or only apply to highbase?)

Answer 26

This is a problem I solved, but now I am curious whit what techniques it can be improved. The original language is Java but here it doesn't matter.

You start with a list of n strings with a length of 7 characters. What is the most efficient algorithm (fastest) to determene the longest substring all the elements have in common, excluding the first character.

example 1:
input: "S000001", "S000002", "S000003", "S000004"
expected output: "00000"

example 2:
input: "S020011", "S020012", "S020013", "S020014"
expected output: "02001"

example 3:
input: "S010001", "S000002", "S000003", "S000004"
expected output: "000"

example 3:
input: "S109001", "S22090", "S090003", "S090004"
expected output: "090"

When there are no common substrings the output is null, an empty string etc. but not a caracter [a-zA-Z]|[0-9]

The input is an array of strings, texts or equivalent in your preferred language (not a char[] or binary, etc).

Answer 27

Make a search engine!

code-golf

Background

You are now the first employee of DuckDuckGoogle, a company founded by a Google employee and a DuckDuckGo employee! They have a new vision for search engine! But obviously, they need to make a search engine first! However, they are bad programmers (nobody knows how they were even hired at DuckDuckGo and Google!). So you are assigned the task of making a search engine.

Search engines

There are three parts to a search engine, a web crawler, an indexer, and a searcher.

The web crawler takes a link, and saves the page and stores the page data (the HTML code). It then looks for links in the page and visits those webpages and does the same. It will continue to do this until there are no more links left.

The web indexer will take the text from each page, take each word, and add it to a dictionary of words and the pages it is associated with. If the word is already in the dictionary, it adds the page as a value of that word that is found in the page. For example, lets say www.example.com/index.html contains the text "hello. thanks! goodbye." and the ww.example.com/index.html is linked to www.example.com/hello.html with the. text "hello. goodbye." The crawler would extract the text from the index.html, and find hello.html, and extract the text from hello.html. The indexer would make a dictionary like this:

dictionary ={"hello.": ["www.example.com/index.html","ww.example.com/hello.html"], "goodbye.":["www.example.com/index.html","ww.example.com/hello.html"], "thanks!": ["ww.example.com/index.html"]}

The simplest part of the search engine is the searcher, or retriever. It simply retrieves the value for the search term (i.e. the list of pages the search term is found in) and prints it. That is the final result of the program. So if the search term is "hello.", the program will print ["www.example.com/index.html","ww.example.com/hello.html"]

Now, here is the difficult part. You must take into account punctuation. So "hello" returns the same as "hello." Also the search engine should be case-insensitive. So "Hello" is the same as "hello", which, as we said, is the same as "hello." which was ["www.example.com/index.html","ww.example.com/hello.html"]

Challenge

The challenge is to write a search engine in the least number of bytes as possible. Why? Because your bosses have decided to use 90% of the one hard drive they have (budget problems!) for the Holy Grail part of their project and you only get 10%.

Rules

1. The input is the "seed", a url at which the crawler should start at, and also the search term.
2. The output is a list of webpage urls where the search term is found.
3. The program cannot use builtins for a search engine or even a crawler (or related, like a scraper or spider library).
4. No need to worry about Javascript at all. Assume that the pages will not have Javascript.
5. The webpages are assumed to have HTML 4.0.1 Strict.

Testing

I am pretty sure people know how search engines work. So I will only include two testcases. You can use the websites in the testcases for testing purposes as well.

> "https://www.udacity.com/cs101x/index.html" "crawl"
["https://www.udacity.com/cs101x/index.html","https://www.udacity.com/cs101x/crawling.html"]

> "https://www.udacity.com/cs101x/urank/index.html" "hummus"
["https://www.udacity.com/cs101x/urank/index.html","https://www.udacity.com/cs101x/urank/hummus.html","https://www.udacity.com/cs101x/urank/arsenic.html","https://www.udacity.com/cs101x/urank/kathleen.html","https://www.udacity.com/cs101x/urank/nickel.html","https://www.udacity.com/cs101x/urank/zinc.html"]

Answer 28

Calculate Hello World!

popularity-contest hello-world underhanded

Your goal is to calculate the simple string "hello world" or any other variant.

Rules

• You may not use the characters in this set (inside your code): hHeElLoOwW rRdD!, in any form (character codes, hex codes, etc. not allowed) [only applies for direct use].
• Your program may not take any input from any source.
• Your program may only print hello world or any other variant to standard output (for your language). Again, it may not print anything else.
• Standard loopholes apply (to clarify, they are not forbidden).
• This challenge is underhanded.
• Your program may not use any built-in string of printable characters (for example, string.printable in Python).
• I recommend you be creative.

Remember, this is popularity-contest! Have fun!

Answer 29

Letter Grade Challenge

Create a program that allows the user to input an int between 1 and 100, then grades that number based on standard US letter grades, printing the grade character as a result. Please use Java for this challenge, and like usual code golf challenges, the smallest answer (bytes) wins. For example, if input is 90, then you display A.

Answer 30

Shortest Possible 240 Sided Die Program: Using No Constant Greater than 6

code-golf

Have you ever played Yahtzee with a 240-sided die? No, probably not. Anyway, I came up with the idea of a 240-sided die program, but to make it hard, you cannot use a constant with an absolute value greater than 6. For example, randInt(1,240) wouldn't work. The chances of any number 1-240 must be completely equal, and using expressions that represent numbers with an absolute value larger than 240 is not allowed. For example, randInt(1,4*6*2*5) is against the rules, since 4*6*2*5 evaluates to 240. Standard loopholes prohibited, and you're code golfing.