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

Hexagonify™ a String Block code-challengestringascii-art

Answer 2

Rennab

Reverse banneR

In the language of your own choosing write a program or function that takes as input the output of the super-handy-for-the-farsighted tool banner. And simply outputs the original text.

Example 1a of banner output on Linux:

> banner 'Code Golf'

   XXXX              XX                    XXXX            XX       XX
  X    X              X                   X    X            X      X
 X                    X                  X                  X      X
 X        XXXXX   XXXXX   XXXXX          X        XXXXX     X     XXXX
 X       X     X X    X  X     X         X       X     X    X      X
 X       X     X X    X  XXXXXXX         X   XXX X     X    X      X
 X       X     X X    X  X               X     X X     X    X      X
  X    X X     X X    X  X     X          X    X X     X    X      X
   XXXX   XXXXX   XXXXXX  XXXXX            XXXX   XXXXX   XXXXX   XXXX

Example 1b of rennab program that runs on Linux and takes input from stdin as lines of strings, and outputs to stdout, and supports the characters: [' ', 'C', 'G', 'd', 'e', 'f', 'l', 'o']:

> banner 'Code Golf' | rennab
Code Golf

Example 2a of banner output on Linux:

> banner ':-)'


                   X
                    X
                    X
    X                X
                     X
         XXXXXXX     X
                     X
                     X
    X               X
                    X
                   X

Example 2b of rennab program that runs on Linux and takes input from stdin as lines of strings, and outputs to stdout, and supports the characters: [':', '-', ')']:

> banner ':-)' | rennab
:-)

Choose what ever characters (minimum of 3) you want to support but that effects your score (see Rules below).

Rules

• Program or function - your choice.
• Input the output of banner in whatever format you'd like (eg 2d array of characters, list of strings, reading from stdin straight from the horse's mouth, &c).
• For this challenge we'll use Cedar Solutions' open-source GNU/GPL banner implementation common on Linux. Prints horizontally only with a fixed size.
• Output the original text in whatever format you'd like, return character at the end optional (eg as a string, a list of characters, as output to stdout, &c).
• You can assume only the characters supported are input.
• You must support a minimum of 3 characters.
• Score is calculated by this formula (where \$n\$ is the number of code bytes and \$c\$ is the number of characters supported): \$n - 8c\$.
• Scores can be negative.
• No standard loopholes.
• Lowest score wins.

Questions

• Has this been done before?
• Is the score formula any good? Any and all suggestions welcome.
• Is the question any good? Any and all feedback welcome.

Answer 3

Reversed Iota's code-golf

I didn't invent this challenge, but I find it very interesting to solve.

For every input number, e.g.:

4

Generate a range from 1 to that number:

[1 2 3 4]

And then, for every item in that list, generate a list from 1 to that number:

[[1] [1 2] [1 2 3] [1 2 3 4]]

Then, reverse every item of that list.

[[1] [2 1] [3 2 1] [4 3 2 1]]

Notes:

• 1 being a loose item is allowed, since flattening will not matter with this anyway.
• To preserve the spirit of the challenge, the range has to be 1-indexed.

Answer 4

Is it a doubling sequence?

Posted here:

Is it a doubling sequence?

Answer 5

Posted to main.

Answer 6

Is it a Happy Number? code-golf decision-problem

A repost of this challenge (if I got the policy right).

Given a single positive integer (which can also be taken as a list of digits or a string), output whether the number terminates at 1 . Truthy/falsy follows the language's convention, or you can choose exactly one value for truthy and another for falsy. (This sequence is A007770.)

Your program should theoretically support all non-negative integers; however, if your language doesn't support unbounded integers, you may only support integers up to 2147483647.

Procedure

Suppose you have the number 193.

• Square every individual digit in the number. Therefore the number's individual digits becomes:

[1] [81] [9]

• Sum all these individual digits:

92

• Repeat this procedure until it stabilizes at 1 or a 37-cycle like the following:

37-58-89-145-42-20-4-16-37

It has been shown that the procedure will always produce either one of these two outputs.

Test cases

Here is a sample program generating the test cases. Here is a step by step reduction of all input between 1 and 100.

1 -> true
2 -> false
3 -> false
4 -> false
5 -> false
6 -> false
7 -> true
8 -> false
9 -> false
10 -> true
11 -> false
12 -> false
13 -> true
14 -> false
15 -> false
16 -> false
17 -> false
18 -> false
19 -> true
20 -> false
21 -> false
22 -> false
23 -> true
24 -> false
25 -> false
26 -> false
27 -> false
28 -> true
29 -> false
30 -> false
31 -> true
32 -> true
33 -> false
34 -> false
35 -> false
36 -> false
37 -> false
38 -> false
39 -> false
40 -> false
41 -> false
42 -> false
43 -> false
44 -> true
45 -> false
46 -> false
47 -> false
48 -> false
49 -> true
50 -> false
51 -> false
52 -> false
53 -> false
54 -> false
55 -> false
56 -> false
57 -> false
58 -> false
59 -> false
60 -> false
61 -> false
62 -> false
63 -> false
64 -> false
65 -> false
66 -> false
67 -> false
68 -> true
69 -> false
70 -> true
71 -> false
72 -> false
73 -> false
74 -> false
75 -> false
76 -> false
77 -> false
78 -> false
79 -> true
80 -> false
81 -> false
82 -> true
83 -> false
84 -> false
85 -> false
86 -> true
87 -> false
88 -> false
89 -> false
90 -> false
91 -> true
92 -> false
93 -> false
94 -> true
95 -> false
96 -> false
97 -> true
98 -> false
99 -> false

Answer 7

Posted

Solve a Picross Row

Answer 8

Implement an HTML renderer code-golf ascii-art

Note: This challenge explaination is very much incomplete - it merely contains ideas that will require revising to form a proper challenge post.

The premise of the challenge is to write a program that take an HTML document as an input, and outputs an ASCII equivalent. Obviously, working with real HTML is not possible, so this challenge will use a very limited and modified subset of HTML.

Here is an example of a potential input:

<body>
    <h1>A Document</h1>
    <div>
        <span>Hello, this is some text</span>
        <img> 8 2 </img>
    </div>
</body>

Which would yield the following output:

+--------------------+
|A DOCUMENT          |
|                    |
|+------------------+|
||Hello, this is som||
||e text            ||
||+--------+        ||
|||@~@~@~@~|        ||
|||~@~@~@~@|        ||
||+--------+        ||
|+------------------+|
+--------------------+

HTML elements that will be implemented:

<span> - Renders text between the tags, wrapping when necessary.

Example:

<body>
<span>
    This is a span element.
    You can write text in here.
</span>
</body>

Output:

+--------------------+
|This is a span eleme|
|nt. You can write te|
|xt in here.         |
|                    |
|                    |
|                    |
|                    |
|                    |
|                    |
|                    |
+--------------------+

(Extra explanation needed to clarify whitespace and character set issues)

<p> (Explanations are omitted to save space)

<h1> - <h6>

<div>

<img>

Sandbox questions/remakrs

• I believe it is possible to write an unambiguous and specific set of rules for how an "HTML document" should be rendered
• It will require lots of careful explanation, wording, and ample examples
• However this challenge seems very long and complicated and it seems like it might not be in the spirit of a code golf challenge

What do you guys think?

Answer 9

Solve a 2xN Maze (posted)

Answer 10

Does the naïve fill suffice?

A bot is positioned in a rectangular grid. By preference it will paint in a west direction, but if it cannot it will paint in a south, east or if all else fails north direction. Sometimes this can lead it to fill the grid, but other times it gets stuck. The following examples show how the path (indicated by ascending digits) of the bot on a given grid varies depending on its starting position:

1

The bot is always able to fill a 1×1 grid, since simply by existing it has already painted the grid.

14    21    43    34
23    34    12    21

The bot is always able to fill a 2×2 grid. As a consequence of its painting direction preferences it normally traverses anticlockwise except when it starts in the bottom right corner when it traverses clockwise.

16    21    65    ..    56    65    165    216    321    654     345    456
25    36    14    21    43    34    234    345    456    123     216    321
34    45    23    34    12    21

The bot usually fills a 2×3 grid, except when it starts in the middle right square. On the other hand, it always fills a 3×2 grid; its painting direction preferences cause it to paint clockwise if it starts in the bottom middle or bottom right cell, otherwise anticlockwise.

189    21.    321    87.    987    ...    987    ...    987
276    387    498    165    216    321    236    345    456
345    456    567    234    345    456    145    216    321

The bot is able to fill a 3×3 grid when it starts in one of the even squares. It's mathematically impossible for the bot to fill it when it starts in an odd square, but I have included these positions for completeness.

Your task is to solve the decision-problem of whether the bot is able to fill a given grid from a given starting point. You can assume that the grid size is a positive integer and that the starting point lies within the grid. You can take the grid size and starting point in any consistent order, as separate inputs, a pair of pairs or a list of 4 elements, or any other reasonable input format. The starting point can be 0-indexed or 1-indexed. You can use any two consistent outputs, or you can output using any values that your language considers truthy or falsy, but not both. Please include your input and output format in your answer.

The directions west, south, east or north correspond to decrementing the x-coordinate, incrementing the y-coordinate, incrementing the x-coordinate and decrementing the y-coordinate respectively.

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

Test cases (0-indexed, width height x y):

4 4 0 0 -> True
4 4 1 1 -> False
4 4 2 2 -> True
4 4 3 3 -> True
4 7 1 3 -> False

Answer 11

A Spherical Die

Inspiration

I have a spherical die, but it's a cheap one so it doesn't work properly. When I roll it, it doesn't always land directly on a "face" marking, but instead can result in an ambiguous result ("is that a 6, a 4 or a 2?")

Assumptions

Assume the die is a perfect, evenly-weighted Unit Sphere (i.e. all points on the surface are radius 1cm from the center) , such that a "roll" can result in any point on the sphere being the uppermost point (the "roll value").

Assume that, if the die is placed or rolled such that 1 is at the "north pole", the conventions of a normal die will follow, i.e:

• 6 will be at the "south pole"
• 4, 5, 3, 2 will be on the "equator", clockwise in that order, equidistant around the sphere.

So, before it's rolled, the die looks like this:

The Challenge

Given a simulated roll of the die (i.e. coordinates representing the top of the die after it's rolled) with the conditions above, identify the closest value (1-6) to that point (i.e. what the roll value should resolve to).

Input

A co-ordinate on the sphere.

There are a few co-ordinate systems used for spheres, the two I'm familiar with (and so will provide examples in) are as follows:

• P(1, φ, Θ) where φ is the "azimuth angle" (0..360), Θ is the "polar angle" (0..180)

• P(x,y,z) where \$x^2+y^2+z^2=1\$

(note: the conversion between the two is: x = cos(φ)·sin(Θ); y = sin(φ)·sin(Θ); z = cos(Θ))

for clarity:

• roll "1" is at P(1,n,0)
• roll "2" is at P(1,270,90)
• roll "3" is at P(1,180,90)
• roll "4" is at P(1,0,90)
• roll "5" is at P(1,90,90)
• roll "6" is at P(1,n,180)

Output

The nearest value (1-6) to that point. If the point is equidistant to two or more points, output any one of them.

Usual exclusions etc. apply.

code-golf random mathematics

Answer 12

Note: this challenge is a work-in-progress, so suggestions would be appreciated

Questions for meta:

• How can I prevent people from just using SHA or MD5 one-way compression?
• are these language restrictions fair?
• is this scoring system fair?
• are there any obvious cheap answers?
• what other tags should be added?
• what should the challenge title be?
• will these restrictions adequately prevent people trying to cheat their way through?
• should a limit be put on a password length? Should I limit passwords to ASCII printable characters?

The challenge

Your challenge is to first choose a "password" (please do not use your actual password). Then, you will create a program which will output a truthy value if and only if this password is given as input, falsy otherwise. Your goal will be to make it so others are unable to reverse-engineer this password (and you will keep this password secret for now).

Scoring

The scoring for this challenge is somewhat different than regular code-golf. During the first two weeks from when an answer is posted, other users will have the opportunity to try to crack your password by reverse-engineering your code. If anyone gets your password correct during this two week period, your answer will be marked as cracked. If two weeks pass without users finding the password, your answer can be marked as safe once you share the password (again, please do not use your actual password, you should make up a new one that you don't use anywhere).

Note that you may use any tools at your disposal (online tools, brute-force attacks, modified code, etc) to extract someone else's password from their code.

Of all the safe answers, the one with the shortest source code (i.e. code-golf) wins!

Rules

To make things fair for everyone, you may only use languages that appear on TIO, or languages that have well-written documentation and are used somewhat widely. You must also provide a link to try your code online that anyone can access (as such, you may not use languages behind paywalls like MATLAB but Octave is still on the table because it's free).

Even if you don't want to post an answer, feel free to try to crack any of the existing answer's passwords! If you get a password, you can simply leave a comment on that answer and that answer will be cracked.

Note

If you edit the code in your answer, the two week period will reset! You may edit any explanations in your answer freely (I will verify that any answers marked safe did not cheat).

tags: code-golf

Answer 13

Stroke Count of a Chinese Numeral codegolf Posted

Answer 14

All work and no play but it gets thinner every time

code-golf kolmogorov-complexity

Your objective is to output the unique string with the following properties:

• Each paragraph consists entirely of repetitions of the sentence All work and no play makes Jack a dull boy.
• The first paragraph is a single line with exactly one repetition of the sentence.
• Each line of each subsequent paragraph is shorter than the longest line of the previous paragraph.
• Each line contains as many words of the sentence as possible without exceeding the length limit, and no trailing whitespace.
• Paragraph ends when its next line would be identical of some previous line of the same paragraph, possibly terminating the last sentence early.
• The last paragraph has the same width as the longest word in the sentence (5).
• There's a pair of line ends between each pair of paragraphs, a single line end after the last paragraph, and no line end before the first paragraph.

The string produced by these rules has: 5025 bytes when using Windows line ends (CR LF) or 4796 bytes using Linux line ends (LF); 229 line ends; 103 full repetitions of the sentence and 11 partial repetitions. It can be compressed into a 249-byte deflate stream (bubblegum code). The full string is included below for reference.

All work and no play makes Jack a dull boy.

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boy. All work and no play makes Jack a
dull boy. All work and no play makes Jack
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Answer 15

Make a quine that shrinks and grows

Write a program that outputs another program that is:

• Larger in bytes than the original
• Outputs a program that is smaller than itself that also obeys these rules and is larger than the original program

Basically the output should alternate between larger than the previous program and smaller than it, while increasing in total size as it goes.

Related

Answer 16

Strobogrammatic Numbers

number code-golf

---

Definition

A number which is rotationally symmetrical, i.e., it'll appear the same when rotated by 180 deg in the plane of your screen. The following figure illustrates it better,

(source: w3resource.com)

Task

Given a number as the input, determine if it's strobogrammatic or not.

Examples

• Truthy

1
8
0
69
96
69169
1001
666999
888888
101010101

• Falsey

2
3
4
5
7
666
969
1000
88881888
969696969

Rules

• The number is guaranteed to be less than a billion.
• We are considering 1 in it's roman numeral format for the sake of the challenge.
• Input can be taken as number, or an array of chars, or as string.
• Output would be a truthy/falsey value.
• This is a code-golf, so fewest bytes will win!

---

Meta

• Although I've tried a search, but is this a duplicate?
• Is the challenge's text clear enough?
• Any tricky/interesting test case?

Answer 17

Explain a Code Golf Answer code-golf string

Background

When writing Code Golf answers, it is often a good idea to add an explanation of the code so the reader understands what's going on. For example, this this answer by @Makonede (abridged):

        θ  # last element of
Σ          # the input, sorted in increasing order by
     1¢    # the number of ones of
   %       # modulo
 žJ        # 4294967296
    b      # in binary

The full program is written on the first line, then a blank line, then on each successive line, a little snippet of the program, aligned using spaces with its position in the full program, and then some comments on the right-hand side explaining each part.

I, for one, find writing and aligning these explanations tedious, so let's outsource it to a program.

Task

Given a program as a string, and a list of sets of pairs of start/end indices to form an inclusive range, output each sub-string defined by the indices on a new line, indented to its respective position in the whole string, with a # at the end of the line, padded so that there are two spaces before the # after the last sub-string, ready for the user to add their explanation.

Rules

• You may use 0-based or 1-based indexing
• You are guaranteed to receive valid, non-overlapping ranges, which together cover the whole string
• You may assume the program string contains no newlines, tabs or other unprintable characters, and no double-width characters
• Standard I/O rules and loopholes apply
• This is code-golf, so shortest code in bytes wins

Examples (1-based indexing)

Inputs: abcdwxyz, (1-8)
Output:

abcdwxyz  #

Inputs: abcdwxyz, (5-7), (1-2),(8-8), (3-4)
Output:

    wxy   #
ab     z  #
  cd      #

Inputs: <<<$[grep -c wx $0-grep -c y\z $0];:<<'Q', (6-20), (22-37), (4-5),(38-38),(21-21), (1-3), (39-39), (40-40), (41-45)]
Output:

     `grep -c wx $0`                           #
                     `grep -c y\z $0`          #
   $[               -                ]         #
<<<                                            #
                                      ;        #
                                       :       #
                                        <<'Q'  #

---

Meta

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

Answer 18

Interpret Interval Notation

Answer 19

Implement a zipwith function

Answer 20

Calculate the 'geothmetic meandian' of a set of numbers

Randall Munroe's March 10 xkcd comic "Geothmetic Meandian" defines the 'geothmetic meandian' of a set of positive real numbers as follows.

Define a function F, such that F accepts a set of n positive real numbers and returns the set (a, b, c), where a is the arithmetic mean of the set (the sum of the numbers in the set divided by n), b is the geometric mean of the set (the product of the numbers in the set to the power of 1/n), and c is the median of the set (the average of the middle two numbers in the sorted set when n is even, and the middle number in the set when n is odd). The function F can therefore be applied again to its own output. Iterating F an infinite number of times should cause its three outputs to converge to one value g. This value g is defined as the geothmetic meandian of the original set of positive reals. (For the purposes of this challenge, you may assume this value exists and does not diverge.)

Given a nonempty list of positive real numbers in any convenient and reasonable format and a positive integer q, compute its 'geothmetic meandian' to q significant figures. Standard code-golf rules apply, and the shortest code in bytes wins.

Test cases

[[1], 2] --> 1.0
[[2, 8], 4] --> 4.742
[[1, 1, 2, 3, 5], 6] --> 2.08906
[[1, 2, 4, 8], 6] --> 3.13227
[[1.1, 2.2, 4.4, 8.8], 9] --> 3.44550208

Answer 21

Hide a message in ASCII art and an image

(needs cooler title)

cops-and-robbers steganography

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Cops

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Robbers

Answer 22

Determine Circles

Answer 23

posted lol

Answer 24

Implement an Over function

Answer 25

Death-onacci sequence (WIP)

The traditional Fibonacci sequence grows forever:

0 1 1 2 3 5 8 13 21 ... 1,346,269 ...

and is given by this formula:

f(n) = f(n-1) + f(n-2)

where the initial numbers in the sequence are 0, 1.

However, there's a set of as-yet unnamed sequences, where a previous number 'dies' and is removed from the total.

For instance the sequence for the 5th death-onacci (m = 5) is given by

f(n) = f(n-1) + f(n-2) + f(n-3) + f(n-4) - f(n-5)

And the first m-1 numbers is 0, followed by a single 1 (so for m=5 the sequence start 0 0 0 0 1)

Test cases:

Here are some test cases:

n	f(n), m=3	f(n), m=4	f(n), m=5
0	0	0	0
1	0	0	0
2	1	0	0
3	1	1	0
4	2	1	1
5	2	2	1
6	3	4	2
7	3	6	4
8	4	11	8
9	4	19	14
10	5	32	27
11	5	56	51
12	6	96	96
13	6	165	180
14	7	285	340
15	7	490	640
16	8	844	1205
17	8	1454	2269
18	9	2503	4274
19	9	4311	8048
20	10	7424	15156
21	10	12784	28542
22	11	22016	53751
23	11	37913	101223
24	12	65289	190624
25	12	112434	358984
26	13	193620	676040
27	13	333430	1273120
28	14	574195	2397545
29	14	988811	4515065
30	15	1702816	8502786
31	15	2932392	16012476

You must write a function or program that takes one number M, and prints out the first 31 M-Death-onacci numbers. M will be a whole number larger than 0 and less than 31. The output can be in any human readable format, and you can take input in any reasonable manner. (Command line arguments, function arguments, STDIN, etc.)

As usual, this is Code-golf, so standard loopholes apply and the shortest answer in bytes wins!

Answer 26

Do I need a win streak?

Answer 27

Gelatin integer metagolf

Answer 28

Drawing the Stack Overflow logo

Answer 29

Reveal by Halves (in need of a better name)

array-manipulation code-golf subsequence

Inspired by this: http://nolandc.com/smalljs/mouse_reveal/ (source).

A valid answer:

• Takes a number \$w\$ and (assumed non-negative) integer \$x\$.
• Outputs an integer list with a length of \$2^w\$, initially filled with zeroes.
• For each number \$n\$ from \$0\$ to \$w-1\$ (inclusive), divide the list into sub-lists of size \$2^n\$, then increment all of the values in the sub-list that contains the index \$x\$.

Examples

(with coordinates from left, 0 indexed, but your answer may have change these)

w=3, x=1
23110000

w=2, x=2
0021

w=3, x=5
00002311

w=4, x=4
1111432200000000

w=2, x=100
Do not need to handle (can do anything) because x is out of bounds

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Meta questions

• Are these tags fitting?
• Would this be better in one dimension? (like \$3, 2\$ returns 11320000) Edit: I've changed it to one dimension but I can revert if it makes it less interesting.
• Should \$w\$ or \$2^w\$ be the input?
• Is this a duplicate?

Answer 30

I'm Lazy*: Top-left align my text

code-golfstringarray-manipulationmatrix

posted