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

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• Parts of the challenge you found unclear
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Answer 1

Output all of printable ASCII using all of printable ASCII

Posted

Answer 2

Count the Collatz survivors mod 2^n code-golfnumbernumber-theory

Answer 3

Round a Matrix

Your input is a 2d array of nonnegative floats A. It can be supplied in whatever format is most acceptable for your language. It can have any dimensions.

Let r and c be the 1d arrays of row and column sums of A respectively, rounded to the nearest integer, with the rule that 0.5 is rounded up to 1.

Your task is to output a 2d array of nonnegative integers B such that |b_{ij} - a_{ij}| < 1 for all i and j, and also the row and column sums of B are equal to r and c respectively.

In other words, B is obtained by rounding each element of A up or down, in such a way that the row and column sums are preserved.

There may be many possible solutions. In this case, you only need to output one of them.

If there is no solution, your program's behaviour can be undefined.

Example:

 A = 1.2 3.4 2.4
     3.9 4.0 2.1
     7.9 1.6 0.6

in this case, the row sums are [7.0, 10.0, 10.1] and the column sums are [13.0, 9.0, 5.1] so after rounding these, you get r = [7 10 10] and c = [13 9 5]. One acceptable solution is

 B = 1   3   3
     4   4   2
     8   2   0

This is code golf, so the shortest code wins.

Motivation

I am also interested in what clever algorithms people can come up with. I guess the most obvious is just to do a random search, but that can take a very long time, even if the array is only 10x10 or so.

Questions

• Is it clear? Please can you edit it if it's not in the right format?
• Has it appeared here before? (I don't think so, because I was searching Stackoverflow for a while in order to come up with a solution to this.)
• Is there always a solution under the conditions given here?
• Would it be better in some other format than code golf?
• Should the condition |b_{ij} - a_{ij}| < 1 be |b_{ij} - a_{ij}| <= 1?

Answer 4

The Fibonacci Rectangular Prism Sequence (posted)

Answer 5

I only want some primes, not all of them

It is well known that there are various formulae for calculating primes that span from calculating a subset of primes, to all possible primes. However, for this challenge, I only want a specific subset.

You are to write a program which takes a single natural integer \$n>0\$ as input. This program will then output a function, \$f(p)\$, which will take a integer \$p\ge0\$ and do the following:

• If \$p < n\$, return the \$p\$th value of a contiguous subset length \$n\$ of primes
• If \$p \ge n\$, returns a non-prime integer (including \$0\$, \$1\$ and negative integers).

For example, Euler's quadratic \$p^2+p+41\$ returns the \$p\$th value of the subset of primes \$\{41, 43, 47, ..., 1601\}\$ for \$0 \le p \le 39\$. However, for \$p=43\$, this returns \$1933\$, which is prime, so this would not be a valid function to return for \$n = 40\$.

You may choose the subset (and it may differ for different \$n\$), so long as it is finite and contiguous. You may also choose to use 1-indexing for \$p\$, meaning that \$f(p)\$ returns primes for \$1 \le p \le n\$.

You may output in the most natural form of a function in your language. For example, Jelly would return a string representing a link, Python would return a named function or lambda etc.

This is code-golf so the shortest code in bytes wins.

---

Meta

• Thoughts and feedback?
• Is this a duplicate?
• Tags are code-golf, primes, functional-programming. Any others?

Answer 6

Question has been posted

Answer 7

Middle-Square RNG: What Number Came Before? (WIP)

A well-known, but statistically poor, way of generating random numbers is to square the number and take the middle digits (when expressed in base 10)

Your task is to take a 4-digit number as input and output any 4-digit number that produces the input number (there may be more than one, which is one of the statistical flaws of this method) when applying middle-square. If the square has an odd number of digits, take an extra digit off the left side.

If there is no such number (some numbers with this method have no predecessor- yet another statistical flaw), indicate that clearly in a way that cannot be mistaken as a valid answer. Some possible ways of indicating this:

• Output nothing
• Output null/None/nil/false
• Output an empty list
• Output a negative number
• Output an error message that is clearly not a 4-digit number
• Throw an exception
• Crash
• Exit with a nonzero status

code-golf random

Answer 8

Operational countdown

code-golf

• Posted.

Answer 9

A Snake, A Camel And A Kebab.

As many of you will know, almost every programming language has a standard casing system; unfortunately, we have not been able to agree on a singular system to use and now must frequently switch between camelCase, snake_case and kebab-case.

Now I know what you're thinking... wouldn't it be nice if we had a program that could convert from one casing to another?
Well - soon we're going to have plenty!!! (This is where you come in)

Challenge

You're job is to write a program/function that will take an input string, and a casing system. It will then print/return the converted string.

Inputs:

You're program will receive two inputs, an alphabetic string that is to be converted and a string that will always be one of kebab camel or snake.

Outputs:

You're program should output a string that conforms to the new casing if it is possible. If the input string was invalid, and had mixed casing, you're program should print/do nothing.

Test Cases:

Valid Examples:
"aJavaVariable", "snake" = "a_java_variable"
"a_python_variable", "kebab" = "a-python-variable"
"golf", "camel" = "golf"
"", "snake" = ""
"doHTMLRequest", "kebab" = "do-h-t-m-l-request"

Invalid Examples (no output):
"an_InvalidName", "kebab"
"invalid-inPut_bad", "camel"

Additional Info:

• As most programming languages prefer lowercase variable names, you should convert all letters to lowercase unless it is needed to be upper case for camel casing.

---

Meta

• Is this a duplicate? I couldn't find any quite like it.
• Are the rules clear?
• Would it lead to more creative answers if I remove the possibility of being given invalid input, and assume all input will be valid?

Answer 10

How Many Atoms?

code-golfchemistryparsingstring

Post

Answer 11

Based Palindromes

Answer 12

Partial sums of the kempner series code-golf math sequence

Posted

Answer 13

Eye test - How many squares are in this picture?

Answer 14

Run the lottery

Rules

Your job is to write a program to accept lottery tickets, adding all the money to a pool, and divvy out the winnings based on how many numbers each ticket has guessed correctly. The amount of money people spent on their tickets is used to determine how much each person should take home.

1. You will receive a list of lottery tickets, which will be how much the person has paid, along with 5 numbers between 1 and 25. The numbers do not have to be unique, and order matters. [1, 2, 3, 4, 5] and [3, 2, 1, 4, 5] are considered different, and [1, 1, 1, 1, 1] is a valid ticket.
2. You will also receive 5 numbers between 1 and 25, which are the winning numbers. This follows the same restrictions as a participant's ticket.
3. Each participant will be given a "score" based on how many numbers they guessed correctly. They must guess the number, and guess it in the correct spot as well. [x, x, 1, x, x] is not a winning number for [1, 2, 3, 4, 5]. [1, 1, 1, 2, 3] counts as 2 correct guesses for [1, 2, 1, 1, 1].
4. The score is \$4^n\$ where \$n\$ is the number of winning numbers. Yes, a participant with 0 correct numbers has a score of 1, and is eligible to take home some money.
5. Each participant's final weight is their score times the amount they spent on the ticket. A person with a score of 4 (1 correct guess) and paid $4 for a ticket has the same weight as a person with a score of 16 (2 correct guesses) and paid $1 for their ticket.
6. Finally, the prize pool is then divvied up. 10% goes to you, the lottery company. The remaining 90% gets divvied up proportionally by each participant's final weight, rounded to the cent.

The input and output of the program can be in any format. The only stipulation is that monetary values must be decimals. For instance, $15.68 cannot be represented as 1568.

Example game

The winning numbers are as follows

• [2, 18, 1, 15, 7]

Four people bought tickets with the following prices and numbers

• $6, [9, 5, 6, 15, 22], one match, score of 4, weight of 24
• $2, [2, 25, 17, 7, 7], two matches, score of 16, weight of 32. Notice how only the second 7 counts, order matters
• $67, [11, 16, 9, 20, 16], no matches, score of 1, weight of 67
• $1, [12, 19, 6, 25, 2], no matches because the 2 is in the wrong spot, score of 1, weight of 1

The total pool is $76, $68.4 after we take our cut, which is then sent out based on the weights. The sum of all weights is 124.

• First ticket gets 24/124, $13.24
• Second ticket gets 32/124, $17.65
• Third ticket gets 67/124, $36.96
• Fourth ticket gets 1/124, a whole 55 cents

Answer 15

Is each bracket matched?

code-golfdecision-problembalanced-string

Given a string consisting only of the characters ()[]{}, determine if each type of bracket is matched--that is, every ( corresponds to one later ), every [ corresponds to one later ], and every { corresponds to one later } (and vice-versa).

Pairs are allowed to overlap: ([)] is just as valid as ([]).

Output one consistent value for one classification and anything else for the other, or following your language's truthiness semantics (inverted if you want).

Test cases:

Matched:

()
[]
{}
()[]{}
()()([])
{[][}]
{{{}}}
([{}]){([]})
[(()())(((())))(]()(()))

Not matched:

(
]
{{}
[)
(()())((((()))))(()()(())(())))
{}{}{)
[())[])]
)(

Meta

• Does this admit a variety of interesting solutions?
• Would it be better to add <> as a bracket type? Have fewer bracket types? Arbitrarily many?
• I'm writing this up entirely because I'm surprised it hasn't been asked yet, so although I have looked, this might still be a duplicate.
• Although I don't think it's necessarily unclear, I feel like the specification could be worded better.

Answer 16

Is this a valid Irish word?

code-golf natural-language decision-problem

In Irish, most consonants are divided into broad (velarized) and slender (palatalized) variants, and the orthography marks them with neighboring vowels, which are similarly divided. This gives rise to the caol le caol agus leathan le leathan (slender with slender and broad with broad) rule – a medial sequence of consonants must have the same class of vowel on either side: in leabhar, bh is surrounded by two broad vowels, so it is broad as well, and in cailín, l is surrounded by two slender vowels, so it is slender. a, o and u are broad and e and i are slender (similar with the vowels with the fada: á ó ú é í); ae is also considered broad.

Given a word, output whether it follows this rule.

Input

You may assume that the input has only the following characters with their uppercase variants:

aábcdeéfghiílmnoóprstuú
AÁBCDEÉFGHIÍLMNOÓPRSTUÚ

Tests

Valid:

deartháireacha
madra
nuachtán
gaolta
ceannasaithe
snámhann
fómhair
laethanta
béar
Bealtaine
hAoine
ball
tree
ggg

Invalid:

codegolf
delta
alishanoi
ABI
anseo
breithlá

(Note that anseo and breithlá are Irish words, but they happen not to follow this rule. You should still output a falsy answer for them for the sake of simplicity.)

Answer 17

Count strictly overlapping substrings code-golf string counting subsequence

Posted

Answer 18

Pad a jagged array to be square code-golf array-manipulation

Posted

Answer 19

Snail word

Very similar to other challenges

Answer 20

Reconstruct an integer from its prime exponents

Answer 21

Draw four colorful quarter circles

The challenge is to reproduce this image in your favorite language:

• Your image must be at least 400 by 400 pixels.
• The fill colors don't need to be the same as in the image but they must be different from each other.
• You must include the outlines but they can be any visible thickness you choose.
• The quarters should be at the same orientation as in the image.
• Your image must have four quarter circles aligned as in the image which each touch the edge of the circle at a point.
• Your code must take input which specifies the location, in pixels, of the point where the quarter-circles meet; you can take this input in any reasonable format, but the units must be pixels (no relative units, such as a fraction of the width/height of the image). You can assume these inputs are always within the bounds of the outer circle. You can also assume that the inputs are such that all four quarter circles can be drawn within the circle.

Here is some LaTeX code as an example:

\documentclass[tikz,margin=3mm]{standalone}
\usetikzlibrary{calc,through}

\usetikzlibrary{intersections}


\begin{document}
\begin{tikzpicture}[inner sep=0pt, outer sep=0pt]

  \coordinate (point) at (-0.1,0.4);

  \draw [name path=mycirc] (0,0) circle [radius=1];
  \path [name path=di-1] (point) -- ++(-2,2);
  \path [name path=di-2] (point) -- ++(-2,-2);
  \path [name path=di-3] (point) -- ++(2,-2);
  \path [name path=di-4] (point) -- ++(2,2);
  
  \foreach \col [count=\i] in {yellow,red,blue,brown}{
  
      \fill [red, name intersections={of=mycirc and di-\i}] (intersection-1) circle [radius=0.05] node (inter-\i) {};
      
      \fill[\col,draw=black,rotate around={(\i+3)*90:(point)}] (point)
        let \p1 = ($(point) - (inter-\i)$) in 
        arc [start angle=0, end angle=90, radius={0.707*veclen(\x1,\y1)}]
        -- +(270:{0.707*veclen(\x1,\y1)}) -- cycle ; 
  }
  
  \fill[red] (point) circle [radius=0.05];
   
\end{tikzpicture}
\end{document} 

code-golf

[I would love help on how to improve this challenge.]

Answer 22

Gray code... Gray code?

Your Task

Your task is to print (in an easily readable and consistent format) the binary representations of the numbers 0-255 in some order such that only one bit is altered between two consecutive numbers.

Your Restrictions

Each successive byte of the source code after the first can only change one bit from the previous byte.

Other Information

Example valid code (in utf-8): q1!#c. Here, q (01110001) and 1 (00110001) are different in only one bit, and so on

Example invalid codes (in utf-8): Q1!, "!"

Example valid outputs (seperated by an empty line):

10101010 10101011 11101011 ... 01010101

[10, 11, 1011, 1111, 1110, ...]

10
0
1
11
111
...

Example invalid outputs (seperated by an empty line):

0000000100000011000000100000000000000100...

0
01
10
11
100
...

0 1 ... 100000000 110000000 ... 11111111

00 01 11 10 0100 0101 ...

0 1 3 2 5 6 ...

Notes:

• A character can be stored as two bytes, but the bytes must differ by only one bit
• If your interpreter ignores a character (like Whitespace ignores almost all characters) it cannot be used

Answer 23

Subarrays With At Least N Distinct Integers

Answer 24

Tri tri tribonacci

Tribonacci from Wikipedia:

The tribonacci numbers are like the Fibonacci numbers, but instead of starting with two predetermined terms, the sequence starts with three predetermined terms and each term afterwards is the sum of the preceding three terms.

The challenge

Given three arrays of three integers, for each array:

1. Find the generator G (the first non-negative integer) of the sequence to which the three numbers belong
2. Then find the G-th element of the sequence (zero-indexed*)

The three integers found are indeed part of a tribonacci sequence, output the G-th element of that sequence.

_{*The sequences are zero-indexed because G may be 0 and in that case you have to find the 0th element of the sequence.}

Example

Given the input

[[5, 11, 20], [1, 2, 3], [23, 39, 67]]

5 11 20 are part of the sequnce 2 4 5 11 20, which starts with 2, so we take the 2nd element of the sequence: 5

1 2 3 are part of 0 1 0 1 2 3, so we take 0

23 39 67 are part of the sequence 7 11 5 23 39 67 129 235 so we take 235

Now 5 0 235 are part of the sequence 230 5 0 235 so the output is the 230th element of that sequence:

174892031986606286607812889236621806383715371411020300455075910

Input / output

You can take the input as you prefer: an array of three arrays, three arrays, an object, a string, etc.

You are not required to handle integers larger than those implemented by your chosen language, I will post plenty of test cases with smaller output after I make a program for the challenge.

This is code-golf, everyone wins.

Meta

Please say something.

Answer 25

Integer partitions into fixed parts with coprime constraint, and exclusion set

codegolfnumber-theoryinteger-partitionsrecursion

Background

Let \$a\$ \$\in \mathbb{N}\$, \$b\$ \$\in \mathbb{N}\$, \$c\$ \$\in \mathbb{N}\$ and \$S\$ be some subset of \$\{i:1\leq i\leq a\}\$.

Consider \$X(a ,b, c, S)\$: The number of integer partitions of \$a\$ into \$b\$ many parts, where each of the parts are co-prime to \$c\$ and no part is contained within \$S\$.

Formally, for \$b=2\$

$$X(a ,2, c, S) = |\{(x, y): x + y = a,\ gcd(c, x) = gcd(c, y) = 1, x \notin S, y \notin S,\ x \leq\ y\}|$$

Challenge

Codegolf, standard rules apply. Write code to calculate the function \$X(a ,b, c, S)\$ above.

Inputs:

• \$a\$, an integer. Your function does not need to be correct for \$a \le 2\$.

• \$b\$, an integer. Your function does not need to be correct for \$b \le 1\$.

• \$c\$, an integer.

• \$S\$, can be any set of integers between \$1\$ and \$a\$ (inclusive). The elements of \$S\$ are unique.

Test-cases

Below test cases are written in the following format: \$a, b, c, S =\$ Answer

3, 2, 2, {} = 0
4, 2, 2, {} = 1
4, 2, 3, {2} = 0
7, 3, 5, {} = 3
7, 3, 2, {5} = 1
11, 3, 1, {} = 10
11, 3, 2, {} = 4
11, 3, 3, {5, 7} = 1

BONUS

Brownie points for anyone who can do either of the following:

1. Disprove the following recursive relationship.
2. Extend the following recursive relationship (for higher values of \$b\$), and/or write code utilising it.

Recursive formula for \$b = 3\$ (Might be incorrect):

$$X(a ,3, c, S) = \sum_{i=1}^{i=\lfloor\frac{a}{2}\rfloor} {X(a - i, 2, c, T_i)} $$

With

$$T_0 = S$$

and,

$$T_i = T_{i-1}\cup\{i - 1, a + 1 - i\},\ for\ i \geq 1$$

Questions for sandbox

Is this challenge good to go?

Answer 26

Decompress an integer, Jelly style

Answer 27

(Σ*)² ⟲ Σ* (aka Round-Trip a String Pair)

Answer 28

Unique languages

As we found out before, each of the 680 languages on Try it online! has a "TIO uniqueness", defined as the length of the shortest substring that appeared in the language's name and no others'.

This time, we're going to make it more general. Given a list of strings S and a target T, output the length of the shortest substring of T that is not in any other element of S. You may choose whether T is part of S or not. The elements of S will always be unique. All elements of S, and T, will only contain lowercase letters (abcdefghijklmnopqrstuvwxyz). You may also take input as uppercase if you wish.

Your score will be calculated as code length × TIO uniqueness, where code length is measured in bytes and TIO uniqueness is the TIO uniqueness as specified here. If a language has an undefined TIO uniqueness, it cannot compete in this challenge.

The answer with the lowest score wins.

Meta

• Is this clear enough?
• Thoughts on the scoring?
• Tags are code-challenge, string, subsequence. Suggestions?
• Any further feedback?

Answer 29

Check B-powersmoothness - posted

Answer 30

Quoted rational numbers