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

Largest number with no repeating substrings of length \$l\$

Inspired by this question, in turn inspired by this one.

When I read the above questions, I thought: "Cool". And then I thought "What if we go further?"

Therefore, in this challenge, you must find the largest number that has no repeating substrings of length n. This is code-golf: fewest bytes wins.

Meta Stuff

This seems insanely hard - is it well specified enough?

Any changes that seem reasonable to add?

Answer 2

Iterated ultimatum koth

Each round, players are paired. One player is the Proposer and the other is the Receiver.

The Proposer must choose a number x such that 0 < x < 100. The Receiver must then Accept or Reject this offer. If accepted, the Proposer gains x points and the Receiver gains 100 - x points. If rejected, neither player gains anything. This is repeated several times, then the Proposer and Receiver roles are reversed, then new pairings are made.

Repeat.

The idea is that the Proposer must try to maximise his own gain, while the Receiver can try to coerce the Proposer to give a larger share of the 100 points by rejecting unfair offers.

https://en.wikipedia.org/wiki/Ultimatum_game

Meta

• Too similar to Iterated Prisoner's Dilemma?
• Any other feedback?

Answer 3

Solve Encode a Lenguage with score 0. Shortest code wins. Quine rule applies. I'll unlikely post it.

Answer 4

Smallest number of panels to represent \$1\$ through \$n\$ in base \$b\$

Inspired by this question. (I have taken a lot of inspiration from Puzzling recently).

Because not all of you spend all your (non-code-golf) time looking at puzzles, let me explain the relevant details.

The challenge involved figuring out how to express the numbers 1 through 8 in only 8 panels in bases 2, 3 and 4. Today, I want to do the converse.

Your task is to, given a number \$n\$ and a base, \$b\$, find the fewest number of panels to represent 1 - n in base b. By that, I mean taking a single continuous slice of the set of panels, we can represent a number, and we can do that for 1 through n.

To clarify, each panel can take a single base-\$b\$ number, and the goal is to find a way to represent each number from 1 through n as a base b number. A continuous slice is a set of panels such that all the panels are consecutive and in the same order as in the original number - for example, 221001120 - in which every two-digit and one-digit number is represented in reading order, left-to-right, as well as 100. Note that 101 and 111 are disallowed because they are not consecutive, with 0s in between, 110, 122 and 2110 are disallowed because they read from left to right, and 121 and 212 are disallowed because they reorder the panels.

For a bigger example, let us take the base as 3 and the number as 18: a valid solution is 122121110221010011200, as every number between 1 and 18 can be represented in base 3

1: 122121110221010011200

2: 122121110221010011200

3: 122121110221010011200

4: 122121110221010011200

5: 122121110221010011200

6: 122121110221010011200

7: 122121110221010011200

8: 122121110221010011200

9: 122121110221010011200

10: 122121110221010011200

11: 122121110221010011200

12: 122121110221010011200

13: 122121110221010011200

14: 122121110221010011200

15: 122121110221010011200

16: 122121110221010011200

17: 122121110221010011200

18: 122121110221010011200

In order to verify your solution does work, provide an optimal answer by the number such that it can be checked.

Input looks like this: n b, and output like this: number solution.

Sample inputs and outputs to aid you (output is represented as o - yes I did work all of these out, and yes, I do believe it is the shortest to just find a place to append the number in):

\$b = 2\$:

n <= 8; o = n (11101000)
n = 9, 10; o = 11 (10011101000)
n = 11; o = 13 (1001011101000)
n = 12, 13, 14; o = 14 (11001011101000)
n = 15, 16; o = n (110010111010000)

\$b = 3\$:

n <= 9; o = n (221001120)
n = 10; o = 11 (22101001120)
n = 11; o = 13 (1022101001120)
n = 12; o = 14 (11022101001120)
n = 13, 14, 15; o = 15 (111022101001120)
n = 16; o = 17 (12111022101001120)
n = 17; o = 19 (12212111022101001120)
n = 18; o = 20 (122121110221010011200)

\$b = 4\$:

n <= 10; o = n (1101220213)
n = 11; o = 12 (231101220213)
n = 12, 13; o = 13 (231101220213)
n = 14, 15; o = n (33231101220213)
n = 16, 17; o = 18 (10033231101220213)
n = 18; o = 20 (1003323110122010213)
n = 19, 20; o = 22 (100103323110122010213)

(i'm not touching 5+ this took me an hour)

Answer 5

Are these strings within N bit flips of each other? code-golf string binary decision-problem

Given two strings a and b, and a positive integer n, determine if b can be reached by performing exactly n bit-flips on a.

A bit-flip is defined as changing one of the bits in the character encoding of a string from a 0 to a 1 or from a 1 to a 0

The same bit may be flipped multiple times, so the 0110 can be reached in exactly 2 bit-flips of itself, as well as in 0 (e.g. 0110 -> 0100 -> 0110).

Test-cases

Truthy

n   a         b
=======================
1   hello     hullo
3   hello     hullo
5   hello     hullo
69  hello     hullo
4   hello     hello
1   x         h
1   x         p
1   x         y
2   x         q
2   x         l
2   x         x
4   x         l
4   x         x
4   x         w
4   x         e

Falsey

n   a         b
=======================
2   hello     hullo
5   hello     hello
1   x         a
1   x         n
1   x         f
1   x         x

Rules

• You may assume/require:
  • n > 0
  • a and b are the same length
  • neither string is empty
  • both strings consist only of lowercase letters a to z (or uppercase A to Z instead, if you wish)
• You should encode the strings in ASCII (or other ASCII-compatible encoding), but if your language cannot easily handle that, ask in the comments and I'll decide on special rules
• Your code does not need to handle high n or long a or b, but it must work in theory
• You may use any reasonable I/O method
• Standard loopholes are forbidden
• This is code-golf, so the shortest code in bytes wins

---

Meta

• Better title suggestions?
• I limited to ASCII to avoid people finding loopholes that trivialise the challenge. Do you have any other suggestions that would work better?
• Test-case suggestions?
• Is this a duplicate?
• Is this clear enough?
• Any other feedback?

Answer 6

Maximum unique characters code-challenge

Write a program which maximises the amount of unique characters in its output while minimising the size of its source. The program must halt.

Functions for converting a character code to its character in any encoding are disallowed.

Your score is output unique chars / size in bytes, and higher is better.

Meta

• Is this a duplicate?
• Should character code functions be banned?

Answer 7

Time till Friday

Answer 8

Extend the OEIS

On the OEIS, there are a significant amount of sequences which do not have proper continuations to them, in other words, the length of the sequence was cut short by the methods at that point.

An example of this is the sequence in this post before it was extended by this answer.

A sequence that wouldn't qualify for this post would be the fibonacci sequence because while it may have a limit on the OEIS, the end is not due to the method used, but instead due to the large amount of current entries.

Challenge:

Find a sequence on the OEIS that follows the above guidelines and extend it by any amount. Your answer should include the code, an explanation of it, as well as the new entries.

Example Answer

A1327807 
previous largest n=8 number = 100000001
new highest n=12 number = 37812879128

// code
// more code

// explanation of code and how you figured it out

Of course your answer doesn't need to follow that format exactly, it should just be close to it.

Notes:

You must write original code for this challenge. If there is already a program out there, and you're only contribution is running it on a better machine, that is a trivially extendable sequence.

This also goes for answers, as the only thing contributed cannot be simply better hardware.

This is popularity-contest for lack of a better tag, so good luck and have fun!

Answer 9

Do I flip the side?

code-golfsequence

Introduction

When writing on a piece of paper folded \$n\$ times you have \$2^{n+1}\$ sides available to write on. When writing on those sides, you can imagine the following sequence of actions (for \$n=2\$):

1. write on the first side and fill the whole side,
2. flip the paper to the next empty side and write there until filled,
3. now we have to unfold the paper once (at least) to get to the next empty side and "flip" the fold,
4. flip the paper to the next empty side,
5. unfold the paper twice to get to the empty side and "flip" the fold,
6. etc.

Challenge

Given number of folds \$n \geq 0 \$ output the number of unfolds needed to get to the next clear side.
Standard sequence rules apply, so you can:

• Take an index \$k \leq 2^{n+1}-1\$ and output the \$k^{th}\$ term, either 0 or 1 indexing.
• Take a positive integer \$k \leq 2^{n+1}-1\$ and output the first \$k\$ terms.
• Output whole sequence for given \$n\$.

Test cases

n | sequence
----------------------------------
0 | 0 (no unfolds, just a flip)
1 | 0 1 0
2 | 0 1 0 2 0 1 0
3 | 0 1 0 2 0 1 0 3 0 1 0 2 0 1 0
4 | 0 1 0 2 0 1 0 3 0 1 0 2 0 1 0 4 0 1 0 2 0 1 0 3 0 1 0 2 0 1 0

Meta

• Too easy?

Answer 10

Is this a valid Temtem character name?

Given a string of between 0 and 15 (inclusive) printable ASCII characters, determine whether the string represents an acceptable character name for the game Temtem.

The following rules apply to character names:

• Names must have at least 3 letters (a-z)
• Names may have up to 2 total prefixes and/or suffixes of at least one letter
• Prefixes and suffixes must be separated from the name by one of space, hyphen or apostrophe
• The first letter of the name and each prefix may be capitalised but all other letters must be lower case.

Truthy examples:

Daddy's girl
de Morgan
Rip Van Winkle
Spider-Man
X-Men

Falsy examples:

McDonald's
-XX-
'falsy'

Note: Temtem may apply other checks to character names not included here.

As this is decision-problem, Output must be a single consistent value for all valid names. Output for invalid names must be consistent for a given invalid name, but may vary between different invalid names, so for instance a count of errors is an acceptable output format.

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

Answer 11

General Binary Counterman Jr

Related

General Binary Counterman Jr is the son of famed Mr. Binary Counterman. He’s continued in his father’s footsteps, counting strings of numbers in the family tradition. But binary has grown old; he’s not a computer. The General has waited for his father’s popularity to wane, and he has decided the time is nigh. The General is about to generalize!

As a reminder, his father would count the evens and odds like this: 1 1 0 0 1 0 would be read as 1st odd, 2nd odd, 1st even, 2nd even, 3rd odd, 3rd even and it becomes 1 3 0 2 5 4.

But not so the General. Evens and odds are just 0s and 1s mod 2, the General knows this. Instead of reducing mod 2, he likes to reduce strings down whatever mod he pleases. Once he does he counts the residues the same way as his father did, but in whatever mod he damn well wants.

The General has read the algorithms that fans have sent his father. But he believes that his new method will yield sufficiently different strategies as to deserve its own page on the internet.

Challenge

Given two inputs representing a mod m and a list L, the nth occurrence of a given congruence class in the list should be output as the nth integer of that class.

The I/O is very flexible and may take any reasonable format, so long as it doesn’t sidestep part of the problem. For instance, you may take the list backwards or as a string, but you can’t take it already reduced mod m.

This is code-golf, so least bytes wins!

Reference Implementation

Example

In my examples, I will represent the I/O as 3: 5 3 2 8 4 5 9 -> 1 3 2 4 5 6 to represent the reminder. This means m = 2 and L = 1 1 0 0 1 0. But again, you are not required to do it this way. In fact, you’re encouraged to find the I/O scheme that works best for your language and algorithm!

Input: 3: 5 3 2 8 4 5 9

This gets counted mod 3 by its congruence class of [0], [1] or [2]:

L  m       Count       
5 %3  ->  1st [2]  ->  2
3 %3  ->  1st [0]  ->  0
2 %3  ->  2nd [2]  ->  5
8 %3  ->  3rd [2]  ->  8
4 %3  ->  1st [1]  ->  1
5 %3  ->  4th [2]  ->  11
9 %3  ->  2nd [0]  ->  3

Output: 2 0 5 8 1 11 3

Test Cases

The most fun part! How do you like the test cases?

2: 1 3 0 2 5 4 
   1 3 0 2 5 4 

2: 1 1 0 0 1 0
   1 3 0 2 5 4 

5: 1 1 0 0 1 0
   1 6 0 5 11 10 

1: 9 8 7 6 5 4 3 2 1 0
   0 1 2 3 4 5 6 7 8 9 

100: 101 102 103 104 105
     1 2 3 4 5

10: 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3
    3 1 4 11 5 9 2 6 15 13 25 8 19 7 29 23 12 33 18 14 16 22 26 24 43 53 

7: 10 20 30 40 50 60 70 80 90 100
   3 6 2 5 1 4 0 10 13 9

8: 09 18 27 36 45 54 63 72 81 90
   1 2 3 4 5 6 7 0 9 10

12: 11 22 33 44 55 66 77 88 99 110 121 132
    11 10 9 8 7 6 5 4 3 2 1 0

11: 1 1 2 3 5 8 13 21 34 55 89 144
    1 12 2 3 5 8 13 10 23 0 34 45 

4: 2 4 8 16 32 64 128 256 512 1024 2048
   2 0 4 8 12 16 20 24 28 32 36 

Other Cheats

In the interest of making this as flexible as possible for all the masochistic and impossible fun languages, here are other things you may skimp on:

• You may assume list L will only contain single digit numbers.
• You may assume mod m will be a single digit number.
• You may do anything when m = 0, including throwing an error.
• You may assume no leading 0s in the numbers.
• It is less consistent with the pattern, but you may eliminate 0s from your output by starting the count for [0], and only the [0] class, at m instead. Then, in the example program, 1st [0] → 3 and 2nd [0] → 6. It would output 2 *3* 5 8 1 11 *6* instead of 2 *0* 5 8 1 11 *3*
• Feel free to comment any other ideas and I will add them in if they don’t detract from the spirit of the challenge, and primarily serve to give the turing tarpits a hand. If the cheat would be used by mainstream and golfing langs, it’s probably not a good idea.

Please mention what cheats you’re taking advantage of, if any!

Answer 12

Project Euler 001 in constant time

Answer 13

Will the hydra finally die? Part II

Background

This is a follow up question to the question: Will the Hydra finally die?

As before a dangerous A Medusa have released a dangerous Hydra which is revived unless the exact number of heads it have is removed. The knights can remove a certain number of heads with each type of attack, and each attack causes a specific amount of heads to regrow. This time the knights are more impatient and having seen your previous abilities want you to** write a program or function that returns a list of hits which will leave the hydra 1 hit from death

^{Note that this is fundamentally different from Become the Hydra Slayer. in 2 aspects. 1: We are not asking for the optimal solution 2: each attack causes a different number of heads to grow back. this radically changes the approach needed.}

For example:

input: heads = 2, 
       attacks = [1, 25, 62, 67], 
       growths = [15, 15, 34, 25], 

output: [5, 1, 0, 0]

Explanation: The Hydra has 10 heads to start with, we have 4 different attacks and for each attack, growth gives us the number of heads that grows back. hits gives us the number of times each attack is applied. So the number of heads the Hydra has after each attack is

2 -> 16 -> 30 -> 44 -> 58 -> 72 -> 62

Since 62 is a valid attack value (It lies in the attack list), we return True since the Hydra will die on the next attack (be left with 0 heads). Note that the order for when the attacks are done is irrelevant.

2 -> 16 -> 6 -> 20 -> 34 -> 48 -> 62

---

Input

Input should contain heads (an integer), attacks (a list of how many heads can be removed), regrowths (how many heads grow back per attack)

You may take input in any convenient method. This includes, but is not limited to

• A list of tuples (1, 15, 5), (25, 15, 1), (62, 34, 0), (67, 25, 0)
• Lists 2, [1, 25, 62, 67], [15, 15, 34, 25], [5, 1, 0, 0]
• Reading values from STDIN 1 15 1 15 1 15 1 15 1 15 25 15
• A file of values

---

Output

• An array, or some way to easily indicate which hits the knights are to take. Example: 5 1 0 0

Note 1 Say that your input is attacks = [1, 25, 62, 67] and the hydra has 25 heads left, then you cannot output the answer as [1,0,0,0], [0,0,0,1] etc. Your output and input must be sorted similarly. Otherwise it will be very confusing for the Knights.

Note 2: Your program can never leave the Hydra with a negative number of heads. Meaning if the Hydra has 15 heads, an attack removes 17 heads and regrows 38. You may not perform this attack.

---

Scoring

• This is a code-challenge you will be scored as follows: the total sum of hits your code produces from the test data + length of answer in bytes
• Note that how you input and parse the test data is not part of your code length. Your code should, as stated above simply take in some a headcount, attacks, regrowth's and return a list/representation of how many hits each attack has to be performed to leave the hydra exactly 1 hit from death.

Lowest score wins!

---

Test data

       attacks = [1, 25, 62, 67], 
       growths = [15, 15, 34, 25],

use every integer from 1 to 200 as the number of heads. An sample from the first 100 can be found below. Again your program does not have to return these values, it is merely an example of how the scoring would work. As seen below the total sum for each of these hits are 535 meaning my score would be 535+length of code in bytes

   1 [0, 0, 0, 0]
   2 [5, 1, 0, 0]
   3 [3, 2, 0, 0]
   4 [7, 4, 0, 0]
   5 [5, 5, 0, 0]
   6 [4, 0, 0, 0]
   7 [2, 1, 0, 0]
   8 [6, 3, 0, 0]
   9 [4, 4, 0, 0]
  10 [8, 6, 0, 0]
  11 [1, 0, 0, 0]
  12 [5, 2, 0, 0]
  13 [3, 3, 0, 0]
  14 [7, 5, 0, 0]
  15 [5, 6, 0, 0]
  16 [4, 1, 0, 0]
  17 [2, 2, 0, 0]
  18 [6, 4, 0, 0]
  19 [4, 5, 0, 0]
  20 [3, 0, 0, 0]
  21 [1, 1, 0, 0]
  22 [5, 3, 0, 0]
  23 [3, 4, 0, 0]
  24 [7, 6, 0, 0]
  25 [0, 0, 0, 0]
  26 [4, 2, 0, 0]
  27 [2, 3, 0, 0]
  28 [6, 5, 0, 0]
  29 [4, 6, 0, 0]
  30 [3, 1, 0, 0]
  31 [1, 2, 0, 0]
  32 [5, 4, 0, 0]
  33 [3, 5, 0, 0]
  34 [2, 0, 0, 0]
  35 [0, 1, 0, 0]
  36 [4, 3, 0, 0]
  37 [2, 4, 0, 0]
  38 [6, 6, 0, 0]
  39 [2, 0, 0, 0]
  40 [3, 2, 0, 0]
  41 [1, 3, 0, 0]
  42 [5, 5, 0, 0]
  43 [3, 6, 0, 0]
  44 [2, 1, 0, 0]
  45 [0, 2, 0, 0]
  46 [4, 4, 0, 0]
  47 [2, 5, 0, 0]
  48 [1, 0, 0, 0]
  49 [2, 1, 0, 0]
  50 [3, 3, 0, 0]
  51 [1, 4, 0, 0]
  52 [5, 6, 0, 0]
  53 [1, 0, 0, 0]
  54 [2, 2, 0, 0]
  55 [0, 3, 0, 0]
  56 [4, 5, 0, 0]
  57 [2, 6, 0, 0]
  58 [1, 1, 0, 0]
  59 [2, 2, 0, 0]
  60 [3, 4, 0, 0]
  61 [1, 5, 0, 0]
  62 [0, 0, 0, 0]
  63 [1, 1, 0, 0]
  64 [2, 3, 0, 0]
  65 [0, 4, 0, 0]
  66 [4, 6, 0, 0]
  67 [0, 0, 0, 0]
  68 [1, 2, 0, 0]
  69 [2, 3, 0, 0]
  70 [3, 5, 0, 0]
  71 [1, 6, 0, 0]
  72 [0, 1, 0, 0]
  73 [1, 2, 0, 0]
  74 [2, 4, 0, 0]
  75 [0, 5, 0, 0]
  76 [1, 0, 1, 0]
  77 [0, 1, 0, 0]
  78 [1, 3, 0, 0]
  79 [2, 4, 0, 0]
  80 [3, 6, 0, 0]
  81 [1, 0, 1, 0]
  82 [0, 2, 0, 0]
  83 [1, 3, 0, 0]
  84 [2, 5, 0, 0]
  85 [0, 6, 0, 0]
  86 [1, 1, 1, 0]
  87 [0, 2, 0, 0]
  88 [1, 4, 0, 0]
  89 [2, 5, 0, 0]
  90 [0, 0, 1, 0]
  91 [1, 1, 1, 0]
  92 [0, 3, 0, 0]
  93 [1, 4, 0, 0]
  94 [2, 6, 0, 0]
  95 [0, 0, 1, 0]
  96 [1, 2, 1, 0]
  97 [0, 3, 0, 0]
  98 [1, 5, 0, 0]
  99 [2, 6, 0, 0]
 100 [0, 1, 1, 0]
535

Meta

• What would a good scoring method for this type of question be?
• My method outputs 2873 for the total count from 1 to 200, is this too high, too low?
• Feel free to suggest other improvements to my testing data

Answer 14

Transdeletion

Transdeletion is the process of removing a letter from a word and forming another word by creating an anagram from the remaining letters.

If you can do this repeatedly, all the way down to a single letter ("A" or "I", usually, in English), you have formed a "Transdeletion Pyramid".

The Challenge

Given a word list (containing any number of words, up to the max your language can handle) and a starting word, find and output the Transdeletion pyramid.

The word list will include the starting word, and is guaranteed to contain all of the words required to make the pyramid (Sandbox: should it? Or is it a better challenge if it won't always be possible to succeed?). A change of case for any letters of the word is allowed at any time - i.e. dealing with casing isn't part of the challenge. So you can assume all inputs are in lowercase, or uppercase, or whatever suits.

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

Examples

In the form [[wordList],"startWord"] -> [ordered output list]

[["a", "an", "ant"], "ant"] -> ["ant","an","a"]
[["I", "in", "tin", "sink", "ink"], "sink"] -> ["sink","ink","in", "I"]
[["I", "in", "tin", "sink", "ink"], "in"] -> ["in", "I"]
[["a", "I", "tin", "ant", "sink", "an" "ink"], "ant"] -> ["ant","an","a"]
[["FAT", "TALIERA", "INTERLAMINATES", "ULCER", "ALTER", "TALE", "A", "RATE", "I", "ANTICEREMONIALIST", "MATERIAL", "INCOMPETENT", "TRILAMINATE", "TEA", "TEA", "TRIFLE", "NONMATERIALITIES", "FRATERNISATION", "AT", "AT", "ORNAMENTALITIES", "RETAIL", "TAIL", "MATERNALITIES", "TERMINALIA", "LATIMERIA", "FATIMA", "OBSCURE", "LENS", "MATRILINEATE"],"ANTICEREMONIALIST"] -> ["ANTICEREMONIALIST", "NONMATERIALITIES", "ORNAMENTALITIES", "INTERLAMINATES", "MATERNALITIES", "MATRILINEATE", "TRILAMINATE", "TERMINALIA", "LATIMERIA", "MATERIAL", "TALIERA", "RETAIL", "ALTER", "RATE", "TEA", "AT", "A"]

Sandbox Questions

1. Should it be possible that the input contains no valid chains?
2. Should the challenge instead be to find the longest chain, even if it doesn't go down to 1 letter?
3. Should the starting word be provided or would it be a better challenge without it?

Answer 15

Decide Magma's Identity

Objective

Given a magma with 256 elements, decide whether it has the identity element.

Definition

A magma is a set endowed with a binary operation. Let's denote the set by \$S\$ and the binary operation by \$\circ\$.

An element \$e \in S\$ is the identity element if for every \$a \in S\$, \$e \circ a = a \circ e = a\$ holds.

If \$e\$ exists, its existence is unique, for if \$f \in S\$ also is an identity element, \$e = e \circ f = f\$.

Input Format

The binary operation \$\circ\$ itself, as a black-box function, will be inputted.

The type of \$\circ\$ doesn't matter. Possible choices include (type names in C):

• Accepting two chars, returning one char

• Accepting two int8_ts, returning one int8_t

• Accepting two uint8_ts, returning one uint8_t

• Accepting one int16_t (to break bytewise), returning one unsigned char

Ungolfed Solution

Haskell

This implementation is much generalized version of the challenge. It can test an arbitrary finite magma, and will explicitly find the identity element if it exists.

It might seem to have time complexity of \$O(n^2)\$, but it's actually \$O(n)\$.

import Control.Monad
import Data.Maybe

findIdentity :: (Eq a, Enum a, Bounded a) => (a -> a -> a) -> Maybe a
findIdentity op = listToMaybe $ do
    let elements = [minBound .. maxBound]
    e <- elements
    guard (all (\f -> op e f == f) elements)
    guard (all (\f -> op f e == f) elements)
    pure e

Answer 16

Packing Boxes into a Truck

Answer 17

Compile Esolang to Esolang

Based on Convert FRACTRAN to Brainfuck.

• Compile Brainfuck to FRACTRAN
• Compile /// to Brainfuck
• Compile Brainfuck to ///

If you have other ideas, please add them. Be sure it's reasonably doable with simple tarpits, eg Jelly to Vyxal to APL isn't all that fun. If you can make a variation of that fun, that should be posted separately.

If you'd like me to make this into a CW to make it easier to contribute, please comment and let me know!

Answer 18

Make me some puzzles

So, a while ago on Puzzling, I posted this. It basically had a whole bunch of equations that were wrong, and when you figured out how much they were wrong by, and transformed 1-26 into A-z, it yielded the phrase ALLWRONG.

Your challenge is to take a string of letters as input, and output a series of wrong, randomly generated equations that are wrong by the correct amount to yield said string.

Equations must be of the form number operation number = number, where each number is a positive integer less than 100, and the operators are +-*/, although × and ÷ are acceptable instead of */.

I'm going to be quite lenient on the definition of 'random' in this one - all possible equations must have a nonzero chance of appearing for any given letter.

Valid equations should have the result of the left hand side's difference from the right hand side being the correct number to, when 1-26 is transformed into A-Z, yield the corresponding character.

Output can be as an array, newline separated, whatever. Equations don't need to be spaced, that's just for readability. You can even output as a list of [1,+,1,=,3] or something.

Testcases

These are possible outputs, not proper testcases.

A => 1 + 1 = 3
HI => 3 * 4 = 4, 9 * 2 = 9
LOL => 20 / 5 = 16, 7 * 5 = 20, 50 - 23 = 15

Answer 19

Avoid traps, run to an exit! restricted-source

Code layout

Your code shall have:

• One kind of characters as the protagonist. The protagonist must appear exactly once in the source.

• One other kind as the trap. Traps must appear once or more.

• One other kind as the exit. Exits must appear once or more.

No other restrictions.

Objective

The protagonist can move by replacing another character by the protagonist and removing the original protagonist.

Write a program/function that:

• Outputs zero when executed/invoked on its own.

• Outputs a negative number if the protagonist moved into a trap. The output need not be consistent.

• Outputs a positive number if the protagonist moved into an exit. The output need not be consistent.

• All other modifications fall in don't care situation.

Example

Given the following source:

Hello, world!

where H is the protagonist, ls are traps, and os are exits, the source shall output zero.

Then the following sources shall output a negative number:

eHlo, world!

elHo, world!

ello, worHd!

And the following sources shall output a positive number:

ellH, world!

ello, wHrld!

Scoring

The source with the least number of characters (not bytes) shall win.

Answer 20

Answer 21

Group binary shapes together

Answer 22

Two inverse quines

Your challenge is to write two programs A and B such that:

• A outputs B
• B outputs A
• Wherever there is a space character in A, there is a non-whitespace character in B, and vice versa (newlines must be consistent through both)
• This means A and B are the same length in characters.

For example A and B are valid, but A and B are not.

Newlines must be consistent through both, so A \nB and C\n D are valid, but A C and B\nD are not.

Scoring

Your score is the length in bytes of either of your programs. If they're different lengths in bytes, take the average.

Answer 23

Knapsack Paragraph, Format For A Phone

There are several paragraph formatting questions already on the site, where a string of text is split on space or other boundaries in order to fit into a rectangle; but they usually involve specifying a particular width for the formatted paragraph in addition to the supplied text.

For this problem, instead of a fixed width, we want to minimize the perimeter of the bounding box of the formatted text. Because we are developers for a phone app and we have to pay for the border by the inch. Or some other such tom-foolery; actually I noticed that this is a bit of a knapsack problem, and I just like the resemblance to that old folk song "knick-knack paddywack, give a dog a bone".

Challenge

Define a layout of a string T of text as a list of n strings s[i] such that the joined string using spaces as delimiter, i.e. s[0]+' '+s[1]+' '+...+' '+s[n-1] is equal to T.

The semiperimeter of a layout s is n plus the maximum length of any s[i] in s.

Given as input a string T, your submission must output the minimum semiperimeter across all valid layouts of T. Alternatively, you may output a layout which has a semiperimeter which is minimal.

The restrictions on input are forgiving; in particular, you may take T as a list of words (strings without spaces) instead of a single string; so long as the result includes the count of spaces that would be present in the layout when calculating the semiperimeter.

This is code-golf; so the shortest submission in each language is the winner, and will be honored with a parade at some vague time in the near future.

Notes:

Just wanted to get this down; will edit later. Mulling whether to have output be the integer, or an example layout having the minimal perimeter. The former is simpler to construct; but the latter just seems more satisfying as an output.

Answer 24

The Roly-Poly, Square-Wheeled Quine

Moved here. Thank you for the comments.

Answer 25

Your challenge is to write a method that compresses/decompresses strings. It will get two arguments: any string (with any ASCII characters) to compress/decompress, and a boolean. If the boolean is true, compress, else decompress.

It can either print the output to stdout or return the data.

The twist is that your score is equal to the byte count of your source code + the byte count of your source code compressed by the compressor. So if your code was c=>c (which is invalid btw), your score would be 4 + 4 = 8.

Rules

• Standard loopholes not allowed

• The decompression and compression should work.

• Your code should not just return the same data. So this

  c=>c
  

  is invalid

Test function to check the score

If you like, here's a function which checks your (javascript) answer.

function checkCompressor(compressor) {
    const source = compressor.toString();
    const compressed = compressor(source, true);
    const decompressed = compressor(compressed, false);
    if (source !== decompressed) return false;
    return compressed; // Have to get byte count manually
}

Answer 26

Determine the length of a Puyo Puyo chain

Puyo Puyo is a Japanese tile-matching puzzle game currently developed by Sega. The gameplay seems simple but it is actually quite complex.

You have a 12x6 board which you can fill with various colors (typically red, green, blue, yellow, and purple) of Puyo (round slime-like creatures with eyes). Each turn, you control a pair of Puyo that you can manipulate and place on the board not unlike Tetris.

When a pair is placed, gravity is applied to the board. If there is an empty gap underneath one or more Puyo in a column, they fall to fill the gap.

When two Puyo of the same color are adjacent to each other, they link together. When 4 or more Puyo are linked, they pop (disappear). After a group of Puyo pops, if gravity causes another group to pop, then you have created a chain. The goal of Puyo Puyo is to place Puyo so that you create as long of a chain as possible to overwhelm your opponent with nuisance Puyo.

Nuisance Puyo are a special case - they are colorless (usually gray or transparent), but more importantly they do not link together. Instead, they pop when an adjacent colored Puyo pops.

Challenge

Given a Puyo Puyo board in any reasonable format (12 lines of 6 character strings, a 12x6 matrix of characters/numbers, 12 6-character strings in an array, etc.) output the chain length as a number. Standard loopholes apply.

This is code-golf, so shortest source code wins.

Bonus: In Puyo Puyo Tsuu, a hidden 13th row was added above the playfield to allow for longer chains. You will get a -5% score bonus if your program can optionally accept a 13th row.

Test cases

Note: Intermediate board states are shown to demonstrate the game mechanics; you are not required to output them.

Key: Red, Green, Blue, Yellow, Purple, Nuisance, . empty

Output: 4

...... ...... ...... ...... ......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
......>......>......>......>......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
..GBR. ...BR. ....R. ...... ......
..RGBR ...GBR ....BR .....R ......
..RGBR ...GBR ....BR .....R ......
.RRGBR ..GGBR ...BBR ....RR ......

Output: 4

...... ...... ...... ...... ......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
...... ...... ...... ...... ......
......>......>......>......>......
.G.... ...... ...... ...... ......
YG.... ...... ...... ...... ......
NGY... ..Y... ..Y... ...... ......
NGR... Y.R... ..R... ..Y... ......
YBR... YBR... ..R... ..R... ......
YYBR.. YYBR.. .BBR.. ..RR.. ......
BBRR.. BBRR.. BBRR.. ..RR.. ..Y...

Output: 0

......
......
......
......
......
......
......
......
.B....
BR....
BR....
BR....

Output: 19 (requires bonus; sorry, no intermediate states)

..YRYY
GBBYRG
RBYRYY
GBYRYG
RYRGBG
YRGBYG
RYRGBY
RYRGBY
RGGBGB
GBYRBB
RGBYRG
RGBYRG
RGBYRG

The Puyo Nexus chain simulator might be useful while debugging.

Answer 27

Reverse cadaddadadaddddaddddddr

The Lisp language has a family of functions car, cdr, cadr, etc for accessing arrays. For each one, an a defines taking the first item of an array, and a d defines taking the rest.

For example, running cadr on [[1,3,4],5,7] will return [3,4] as the a gets the first item ([1,3,4]) and the d removes the first item.

We've already had a challenge regarding running a cadaddadadaddddaddddddr on a list, but what about the reverse?

Your challenge is to, given a string of the type above (starting with a c, ending with a r, with only ad in the middle), and a single value, create an array such that running the string as a cadaddadadaddddaddddddr on the array returns said value.

For example, given the input cadar, 1 a possible output could be [[0,[1]]] since running cadar on that gives 1.

Scoring

This is code-golf, shortest wins!

Testcases

These are possible outputs, all that matters is that your program returns an array which works for the condition.

car, 3 => [3]
cdddar, 5 => [0,0,0,5]
cadadadadar, 4 => [[0,[0,[0,[0,[4]]]]]]
caaaaaaaaar, 2 => [[[[[[[[[[2]]]]]]]]]]

Let me know if any of these are wrong.

Answer 28

Convince me that this vector theorem is true

code-golfmathlinear-algebra

Background Information

From Wikipedia:

A sequence of vectors \$\mathbf v_1,\mathbf v_2,\mathbf v_3,\dots,\mathbf v_k\$ from a vector space \$V\$ is said to be linearly dependent, if there exists scalars \$a_1,a_2,\dots,a_k\$ such that: $$a_1\mathbf v_1+a_2\mathbf v_2+\cdots+a_k\mathbf v_k=\mathbf 0$$ where \$\mathbf 0\$ denotes the zero vector.

Based on many sources¹ around the internet, it is true that

If there are more vectors than dimensions, the vectors are linearly dependent.

In other words, if the vector space is \$\mathbb R^n\$(the number of entries in each vector is \$n\$), then the sequence of vectors \$\mathbf v_1,\mathbf v_2,\dots,\mathbf v_p\$ is always linearly dependent if \$p>n\ge2\$.

Task

After looking around, I'm still not entirely convinced that the above statement is true. Please convince me with a program that takes in: the dimension \$n\$(you don't have to take this in if you don't need to), and \$p\$ \$n\$-dimensional vectors \$\mathbf v_1,\mathbf v_2,\dots,\mathbf v_p\$, where \$p>n\ge2\$. You can take in \$p\$ in your program if you want to. You can assume that all vector entries in each vector are integer values. The input format can be whatever you choose, as long as there is a clear distinction between each vector. The program should return a list of scalars \$a_1,a_2,\dots,a_p\$, with at least one of them non-zero, such that $$a_1\mathbf v_1+a_2\mathbf v_2+\cdots+a_p\mathbf v_p=\mathbf 0$$ to show linear dependency. If there are multiple outputs that work, you can output any one of them. The output format is also flexible, as long as it is clear what the values of each scalar are.

This is code-golf, so the shortest code in bytes wins!

Example I/O

Input:
\$n=2\$
\$p=3\$
\$\mathbf v_1,\mathbf v_2,\dots,\mathbf v_p=\pmatrix{4\\5},\pmatrix{8\\10},\pmatrix{6\\7}\$

Output:
One possible solution is \$a_1,a_2,\dots,a_p=2,-1,0\$. We can quickly test that this does work: $$2\pmatrix{4\\5}+(-1)\pmatrix{8\\10}+0\pmatrix{6\\7}=\pmatrix{8\\10}-\pmatrix{8\\10}+\pmatrix{0\\0}=\pmatrix{0\\0}=\mathbf 0$$

Test Cases:

Work in progress

n, vectors -> scalars
2, [(4,5),(8,10),(6,7)] -> [2,-1,0]
2, [(3,6),(6,7),(3,9),(2,4),(5,5)] -> [2,0,0,-3,0]
3, [(1,2,3),(2,3,4),(3,4,5),(4,5,6),(5,6,7),(6,7,8),(7,8,9),(8,9,10)] -> [1,-1,-1,1,1,-1,-1,1]

---

¹: Some sources: this, this, this, this

---

Concerns

• Has a similar challenge been done before?
• Is it clear what the challenge is specifying?
• I want to change the title to be more specific, but I'm not sure what to change it to.
• I need some test cases, but I'm not sure what test cases would be good for this.

Answer 29

All valid N * N Flow Free Boards.

Since there are several other Flow Free question, either here or on main, but none, as far as I can tell, that do this, I will ask the question some of us have pondered at night: How many valid Flow Free Boards are there?

What is a valid board?

From what I can tell from my attempts at time trial, a valid board has all of these:

1. Has between floor(2N/3) and ceil(3N/2) flows (where a flow is two distinct points, defined as it's ends, between which a line can be drawn connecting them).

2. No two endpoints of a flow can be adjacent.

3. The board must be solvable - that is, there must be a way that all endpoints of the flows can be connected together such that every square of the board is filled once and only once, and no two paths intersect at all.

Input/Output

Your program will receive N, the side length of the board. The board will always be square (as that is the case in most boards), and it must return all valid boards, and the number of such boards.

As always, you can take input and output in any reasonable format, and shortest byte count wins!

Meta

Has this been done before?

Anything that needs specifying?

Answer 30

Who Won Tic-Tac-Toe?

Your job is to be the judge of a game of Tic-Tac-Toe.

Given an input consisting of three lines (9 characters not including newlines), determine the winner of the game of Tic-Tac-Toe.

For example, for the input

XOO
-XO
O-X

your program should either return or print X.

For tie games or games where no one has won, do not print or return anything.

The only input characters will be 'X', 'O', and '-' (along with two newlines), and the only outputs your program should give are 'X' and 'O' (or nothing).

Also note that the given board will be a valid game of Tic-Tac-Toe, so there will be no situations where both players have winning positions.

More examples:

OOO
---
---

=> O

OXO
--X
---

=> (nothing)

OXO
X-O
X-O

=> O

OXO
XOX
XOX

=> (nothing)