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.

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Answer 1

Least efficient field order

Background:

In C and other languages, a struct is a data type composed of fields of other data types. These fields may be different sizes (in bytes) and may have different alignment requirements (e.g. an int field may need to be on a 4-byte boundary).

Padding is added to a struct to keep all of its fields aligned, and to keep its size a multiple of each field's alignment.

For example:

struct test {
    char  a; // 1-byte, 1-byte aligned
    short b; // 2-byte, 2-byte aligned
    int   c; // 4-byte, 4-byte aligned
}

In this struct, there will be 1 byte of padding after a (to keep b on a 2-byte boundary), no padding after b (as c is already on a 4-byte boundary) and no padding after c (as the size is already a multiple of 2 and 4 bytes), so the total size of the struct is 8 bytes (1 + 2 + 4 + 2). However, if we rearrange the order of the fields, the struct size can be bigger.

struct test_2 {
    char  d; // 1-byte, 1-byte aligned
    int   e; // 4-byte, 4-byte aligned
    short f; // 2-byte, 2-byte aligned
}

In this struct, there will be 3 bytes of padding after d (to keep e on a 4-byte boundary) and there will be 2 bytes of padding after f (to keep the size a multiple of 2 and 4 bytes), so the total size of this struct is 12 bytes (1 + 4 + 2 + 3 + 2).

Challenge:

Given a list of pairs of positive integers (each pair representing the size and alignment of a field), return the same pairs in an order such that a struct with fields in that order would require the most padding, i.e. be the least space-efficient.

Givens:

• A field's size will always be greater than or equal to its alignment. (e.g. (4, 8) is not a valid input pair)

• A field's size will always be a multiple of its alignment. (i.e. (12, 5) is not a valid input pair)

Test cases: (other outputs that give the same total size are valid as well)

[(1, 1), (1, 1), (4, 4)] -> [(1, 1), (4, 4), (1, 1)] # size 12
[(12, 4), (1, 1), (2, 2), (8, 8)] -> [(12, 4), (8, 8), (1, 1), (2, 2)] # size 32
[(7, 7), (5, 1), (2, 2)] -> [(7, 7), (2, 2), (5, 1)] # size 28
[(6, 6), (6, 3), (4, 2), (2, 2)] -> [(6, 3), (4, 2), (6, 6), (2, 2)] # size 24
[(1, 1)] -> [(1, 1)] # size 1

Test case checker online!

Answer 2

The Minigame Challenge

cops-and-robbers code-golf

The idea of this CnR is fairly simple: The Cops must create a simple minigame (explained in more detail below), with a definite goal. That goal may or may not be achievable. The Robbers must then either complete the minigame, or prove its goal is not achievable.

Rules

The Minigame

The Cops will create a suitably simple minigame with a definite goal.

Acceptable minigame examples are functions that take some input and return some output, with the goal being to either achieve a specific output, or make the program terminate or error.

Minigames considered complex (and thus unnacceptable) would be programs/functions that will never terminate in up to 60s (using TIO as a benchmark here), or that simulate complex games (such as blackjack, chess, etc).

Note: I'll try to expand further on what kinds of minigames are acceptable or not. Suggestions are appreciated.

Cops:

The Cops must provide one of the following:

• A solution for your minigame that achieves the goal, or
• A proof that the goal for your minigame is not achievable.

at least 7 days (168h) after the answer was posted for their answer to be considered safe.

If your minigame's goal is achievable, it must always be achievable, and it must not contain "insider information", such as a fixed seed for a pRNG, or pregenerated primes as factors of a number to be factored.

Robbers:

To crack an (unsafe) answer, the robber must provide either a solution to the minigame that achieves the stated goal, or a proof that the goal is not achievable.

Scoring:

Cops will be scored based on standard code-golf rules, with the fewest number of bytes in an answer being better. Cracked answers will always have a score of \$\infty\$.

Robbers are scored according to the number of answers they've cracked.

Standard loopholes are, as usual, forbidden.

Challenge is still under construction

This is the first CnR I've ever come up with. Suggestions and observations are always appreciated.

Answer 3

Challenge

Create a function takes in two 2-dimensional arrays of Characters (or Strings if the programming language does not have characters as a datatype) as inputs: a and b.

Your task is to determine if b contains a. If this is so, return true. Otherwise, return false.

Sample Test Cases

a:

123
456
789

b:

123
456
789

should return true.

a:

code
golf

b:

thisis
code!!
golf!!
ohyeah

should return true.

a:

abcd
efgh
ijkl

b:

abcdef
ghijkl
mnopqr

should return false.

Least bytes wins.

Answer 4

Finding Points in Convex Hulls

Convex hulls are notoriously hard to deal with, so today's challenge will deal with a relatively simple premise: given a convex hull defined by a set of points, and an additional point, find whether the additional point lies in the hull.

Now, for some definitions

1. The convex hull of a finite set X, a subset of R^n, is the set of convex combinations of points of $X$.
2. A convex combination of points x1,x2,...,xn is a point of the form a1x1+a2x2+...+anxn such that all ai>=0 and the sum of all of the ai is 1.

Input/Output

The input is rather flexible, as long as it contains the appropriate information to express the convex hull and additional point.

An example of a valid input format to express the convex hull represented by (0,1,2),(4,3,2),(8,8,8) and the point (5,5,5) is

([(0,1,2),(4,3,2),(8,8,8)],(5,5,5))

The output is a truthy/falsy value, depending on whether the point is contained in the hull.

Remarks

There are a lot of packages and libraries that deal with convex hulls, such as scipy.spatial. Such libraries/packages are explicitly banned. Libraries that facilitate matrix computations, such as numpy, are permitted.

The winning criterion is code-golf.

There is no limit on the number of dimensions the points can lie in, as long as they all lie in the same number of dimensions.

Test Cases

I will be using the following tio link for testing the validity of solutions.

Some smaller test cases:

([(1,1)],(1,1)) - True
([(1,1)],(1,2)) - False
([(1,1,1),(3,3,1)],(2,3,1)) - False
([(1,1,1),(3,3,1)],(2,2,1)) - True
([(0,0),(3,3),(0,6)],(2,4)) - True
([(0,0),(3,3),(0,6)],(1,1)) - True
([(0,0),(3,3),(0,5)],(2,4)) - False

Questions for Sandbox

Is code golf the best criteria for this? That might encourage brute force searches on every combination of points... any suggestions?

Answer 5

This is a post to pre-test for a duplicate question before I spend the time to finish the full post and add test cases.

So, have we ever had a question for a "snake rotation" of a matrix:

    +--------------+
      1  2  3  4  5|
    +------------  |
    |10  9  8  7  6|
    |  +-----------+
    |11 12 13 14 15
    +--------------+


    +--------------+
-->  13 14 15  1  2|
    +------------  |
    | 7  6  5  4  3|
    |  +-----------+
    | 8  9 10 11 12  -->
    +--------------+

The ascii walls are there only for clarity. Actual input/output would be normal matrices

Answer 6

WordArt reader

I've decided to leave this very open ended, so that I can write it based on community input. There are a lot of questions in the bottom. All feedback is appreciated, even minor suggestions/comments. :)

image-processing,classification,code-challenge.

---

Did you know WordArt is still a thing in MS Word? Let's parse it!

^{(I'll remove the Swag format)}

The challenge will contain a test battery with X jpg.files each with a word or sentence shown in WordArt. Your task is to parse as many as you can. The winner will be the submission that correctly parses the most images, with date stamp being the tie breaker.

---

Sandboxing:

• Good idea or not?
• Should there be many different styles, or should I stick to one? Colors? Shade/mirroring?
• How many test cases?
• Is jpg the best format (it was used in the Upgoat/Downgoat challenge)
• Should I have a more refined scoring mechanism? It's hard to mix two quantities into one score.
• Should I stick to just letters / alphanumeric / all printable ASCII / multiple lines? Long sentences or single words?
• Orientation? Waves? Circular?
• Resolution?
• Builtin functions?
• Should I require a complete match of images, or character by character?

Answer 7

How many right triangles can you find?

code-golf math

---

Challenge

You will be given an input represented by x, which is a string containing at least 3 characters. It will consist only of the standard numeric characters, 0 through 9. Your job is to find and output how many right triangles can be formed with the given numbers.

Rules

• Numbers must be kept in the order they were given in. No mixing them up!

• The numbers for each right triangle must be consecutive.

• The order of numbers has to be a first, b second, and c third, and must satisfy the formula a² + b² = c². a can be greater than or less than b, as long as it satisfies the formula.

• Decimal points may be added between any numbers.

• Decimals require one or more numbers to be placed before them, e.g. .5 cannot be used as a number but 0.5 and 12.5 can.

• Decimals with at least 4 digits after the decimal point truncated to the third digit, e.g. 1.2345 would truncated to 1.234 and 1.9999 would be truncated to 1.999.

• Numbers can be used more than once in 2 or more different triangles, but cannot be used multiple times in the same triangle.

• Multiple representations of the same value can count multiple times.

• Repeating zeros are allowed, e.g. 000.5 counts as a number.

• All possible combinations must be taken into account for your program to be valid.

Example Inputs and Outputs

Input: 345
Output: 1
This can be split into 3, 4, and 5, which, of course, form a right triangle.

Input: 534
Output: 0
While this does include the necessary numbers to form a right triangle, they are not in the correct order. It has to follow the formula a² + b² = c², but in this case it follows c² = a² + b². The order of numbers cannot be changed from the original input, so in this case no right triangles can be formed.

Input: 3415
Output: 0
This does contain a 3, 4, and a 5, which can form a right triangle, but they are not consecutive; there is a 1 splitting the 5 from the 3 and 4.

Input: 5567507
Output: 1
Because decimals can be added anywhere, it can be changed to 55.67.507, which allows splitting it into 5, 5.6, and 7.507 to form a right triangle. Remember that decimals are truncated to the third digit after the decimal point, which is how we get 7.507.

Input: 345567507
Output: 2
The first right triangle is formed by 3, 4, and 5. The second one is formed by 5567507 (read the previous example for explanation). Numbers can be used more than once, so the first 5 was used in the first and second triangles.

Input: 51125
Output: 0
Because of rule 5, you cannot use .5, 1, and 1.25. An integer is required before .5 for it to work.

Input: 051125
Output: 0
Unlike the previous example, there is a number before the first 5, so it is now legal to use 0.5, 1, and 1.25.

Input: 121418439
Output: 2
The numbers 12 and 14 would form a right triangle where side c has a length of approximately 18.43908891458577462000. Because long decimals are truncated to the third digit after the decimal point, we would be left with 18.439. This fits in with the original input, 121418439. Additionally, 1.2, 1.4, and 1.843 counts as a separate combination, thus giving us our second right triangle.

Input: 10011005
Output: 8
Numbers count separately if they're represented in different ways, so this allows for (1, 00, 1), (1.0, 0, 1), (1, 0, 01), (1, 0.01, 1), (1, 0.01, 1.0), (1, 0.01, 1.00), (1.0, 0.1, 1.005), and (1, 00.1, 1.005).

---

This is code golf, so shortest answer in bytes wins. Good luck!

Answer 8

\$n\$-Chess KotH king-of-the-hillgridchessboard-game

Introduction

Inspired by the challenge N-movers: How much of the infinite board can I reach?, I came up with an idea of applying the \$n\$-mover rules in chess.

\$n\$-Chess™ is a board game played on a 8x8 grid like the original chess. However, the pieces are very different from chess - they are named \$n\$-movers (\$n\$ can be any natural number) and can only move by the rules set on them (see Rules: Pieces).

Rules

Pieces

In \$n\$-chess, a piece is called an \$n\$-mover, where \$n\$ denotes its possible movements. Specifically:

1. The \$n\$-mover can only move one step of Euclidean distance \$\sqrt n\$ each time, i.e. for a move with \$x\$ units horizontal and \$y\$ units vertical, \$x\$ and \$y\$ must fulfill the equation \$x^2+y^2=n\$ in order to be valid.
   • For example, a 5-mover can only move 1 unit in one direction and 2 units in the another at the same time; while a 25-mover can move 5 units in either direction, or 3 units in one direction and 4 units in the another at the same time.
2. A piece can have at most 2 rules set at the same time. For a piece that can act as either an \$m\$-mover or an \$n\$-mover, we can call it an \$(m,n)\$-mover. An \$(m,n)\$-mover is allowed to move one step of Euclidean distance of either \$\sqrt m\$ or \$\sqrt n\$ or \$\sqrt{m+n}\$.
   • It is allowed to have \$m=n\$.
   • Only pieces that has captured other pieces can have multiple rules (See Rules: Capture).
3. If more than 2 rules are set on a piece, only 2 rules can be reserved. You can choose which 2 rules to reserve.

Board

The chess is played on a 8x8 board. The initial setup is as follows:

Capture

1. If a piece lands on a grid that an opponent piece has occupied (capture), that opponent piece shall be moved away from the board.
2. After that, the piece will be granted rules from the captured opponent piece. As stated in Piece, if there are more than 2 rules in total, only 2 shall be reserved.

Playing

1. In a turn, White and Black play a move in turn. White always moves first.
2. Only one piece can be move per turn.
3. You cannot move a piece in the way that is not allowed by the rules set on it, beyond the boundaries of the board, or onto a grid already occupied by your other pieces.
4. You cannot move your last piece in the way that after moving it it can be captured instantly.

Victory Condition

The game ends with either player winning if:

1. The last piece of the opponent is being checkmated, i.e. no possible moves that can save this last piece from being captured; or
2. The opponent resigns and loses. (In this challenge, no resignation will be allowed)

The game ends with a draw if :

3. No checkmate is possible for both sides;
4. Either player has no more possible moves, but is not in checkmate;
5. There is no capture in 50 moves; or
6. The identical board arrangement has appeared 3 times with the same player to move.

Implementation

A player bot is a class that implements a function nextMove(). This function receives 3 arguments and output an array of 6 integers:

function nextMove(
    color: int,                    // Your color: 0 = white, 1 = black
    board: int[8][8][3],           // Current board:
                                   //  First index: x-coordinate
                                   //  Second index: y-coordinate
                                   //  The third layer will be as follows - 
                                   //   [0]: the color of the grid
                                   //       (-1: Not occupied; 0: white; 1: black)
                                   //   [1]: rule 1 (0 if not exists)
                                   //   [2]: rule 2 (0 if not exists)
    moves: int[][10]               // Previous moves:
                                   //  First index: move number (0-indexed)
                                   //  The second layer will be as follows - 
                                   //   [0]: the color of the player
                                   //   [1]: is this a capture (0: no, 1: yes)
                                   //   [2]: source x-coordinate
                                   //   [3]: source y-coordinate
                                   //   [4]: source rule 1
                                   //   [5]: source rule 2 (0 if not exists)
                                   //   [6]: target x-coordinate
                                   //   [7]: target y-coordinate
                                   //   [8]: target rule 1
                                   //   [9]: target rule 2 (0 if not exists)
): int[6]                          // Return value: as follows:
                                   //  [0]: source x-coordinate
                                   //  [1]: source y-coordinate
                                   //  [2]: target x-coordinate
                                   //  [3]: target y-coordinate
                                   //  [4]: target rule 1
                                   //  [5]: target rule 2 (0 if not exists)

• Rule 1 and Rule 2 denotes the 2 rules a piece has.
• Source rule entries are used to denote which rules a piece has, while target rule entries are used to denote which rules are decide to keep.

You may use JavaScript, pseudo-codes, or any languages similar to JavaScript, but using JavaScript is strongly encouraged, because all submissions will be translated to JavaScript before using for competition, and the test drive only supports JavaScript.

Restriction

1. Standard loopholes are forbidden by default.
2. You cannot by any means read or modify other bots. You can only use data within the class and inputs passed to nextMove() function.
3. You may define other variables inside your class if needed.
4. You may use a random number generator.
5. Your bot, specifically the nextMove() function, must return value in 10 second per move. Timeout leads to disqualification.

Procedure

Round-robin will be used to determine the opponents, i.e. all bots will face each of the other bots twice, one as black and one as white. For each game, a win gets 2 points, a lose gets 0 points, and a draw gets 1 points.

The bot will the highest points wins, and if there are any ties, they will be broken by:

1. Number of victories;
2. Average time to checkmate opponent (shorter is better); and
3. Drawing lots. (Hopefully this step is not necessary)

TODO

• Add a sample implementation.

Answer 9

Multi-Digit × Single-Digit Checker code-golf arithmetic

Introduction

The story below is fictional, don't worry.

Times table hard. More curriculum. Class advance. Son behind. Horror. Help.

ahem Pardon me.

So... I've got a big problem. The times table is huge, and all the mnemonic rules we've taught our son haven't make him fully memorize it yet. However, his class must advance to the next chapter, long multiplication. As a result, he is prone to making many mistakes while multiplying numbers.

See, they're already making the students multiply a multi-digit number by a single-digit number. My son often forgets to carry digits over and, of course, his times table. The good thing is that he never misses digits!

The situation is awful. Help me before they start with two multi-digit numbers!

---

Challenge

Your challenge is to write a program that takes a multiplier, a multiplicand and a product, and analyzes the product for any of the following mistakes. Here's how:

• If a digit is the correct ones digit of the product of the multiplicand times the digit of the multiplier he's currently multiplying, but a non-zero carryover was supposed to be added to it, then this digit has a carryover error.
• If a digit is otherwise wrong, there's a times table error around it (we can't be sure if the ones digit was wrong or a carryover digit was wrong), so it has a times table error.
• There will never be another kind of mistake in the product, my son doesn't skip digits.

For each wrong digit, return an array of two or three elements:

• Position of the digit from the left or right, 0- or 1-indexed (your choice must be consistent). Keep in mind that, if the leftmost digit is absent due to a carryover error, then it's still the leftmost digit and the place has the relevant index.
• Correct carryover, if the mistake was a carryover error, or omitted otherwise. You may also put a 0 instead of omitting the element (you can't blame my son for forgetting to add a zero carryover!), but be consistent.
• Correct digit.

---

Rules

• The numbers will all be positive integers.
• The multiplicand will be an integer from 1 to 9, inclusive.
• You can get the three numbers via any reasonable way you want.
• The output can be in any order, as can the elements of each array, as long as the latter is consistent.
• You may not make use of any standard loophole.
• This is a code-golf challenge, so the shortest answer, measured in bytes, wins.

---

Test cases

Multiplier, Multiplicand, Product -> Mistakes (0-indexed from the left, possibly absent carryover)

5, 3, 15 -> [] (15)
3, 5, 5 -> [[0, 1, 1]] (05 -> 15)
7, 3, 31 -> [[0, 2]] (31 -> 21)
1551, 9, 4959 -> [[0, 1, 1], [1, 4, 3]] (04959 -> 14959 -> 13959)
2121, 7, 14847 -> [] (14847)
2121, 7, 4727 -> [[0, 1, 1], [2, 1, 8], [3, 4]] (04727 -> 14727 -> 14827 -> 14847)
33333, 9, 11111 -> [[0, 2, 2], [1, 9], [2, 9], [3, 9], [4, 9], [5, 7]] (011111 -> 211111 -> 291111 -> 299111 -> 299911 -> 299991 -> 299997)

---

Sandbox

• Is the challenge unclear?
• Is the output format weird or too strict?

Answer 10

Sandbox Notes

• Any other/better tags?
• Is my math right?

Knot Function

code-golf knot-theory function

TL;DR: Define a closed curve in 3D space that forms a knot.

A function \$f : [0,1] \to \mathbb R^3\$ is considered a loop function if the following conditions hold:

• It is continuous.
• \$f(0) = f(1)\$.
• It is injective everywhere else.

Intuitively, this means that the function traces out a curve in 3D space that does not intersect itself.

Let the set of loop functions be denoted \$\text{Loop}\$. One such function is \$\text{circle}(t) = (0, \sin 2\pi t, \cos 2\pi t)\$, which traces out a circle in 3D space.

A function \$f : \text{Loop}\$ is considered a knot function if there exists no continuous function \$d : [0,1] \to \text {Loop}\$ such that \$d(0) = f\$ and \$d(1) = \text{circle}\$. Intuitively, this means that the loop that the function traces out cannot be continuously deformed into a circle without intersecting itself.

The Task

Write a program or function that implements a knot function, where real numbers are replaced with (to best approximation) floating point numbers.

This is code-golf, so the shortest valid answer (measured in bytes) wins.

Answer 11

Print the sum of the previous answer's ASCII values

answer-chaining

Challenge

Output the sum of the previous answer's characters. For example, if the previous answer was print(25), the next answer would have to output the next answer would have to output 741.

Initial Answer

The initial answer has to output the number 1000

Rules

• Your code can only use ascii characters (sorry Jelly), no extended-ASCII or Unicode characters.
• Your output can be in Decimal, Unary or Base 256 (represented by ASCII characters)
• You cannot use a language that has been used before. (Note: Different versions of the same language are allowed, like Python 2 and Python 3)
• To prevent overly long languages (such as Unary) ruining the chain, your answer cannot be longer then 1000000 bytes.
• The same person cannot post twice in a row
• If two users post "at the same time", the earlier one will stand
• If a solution breaks one of these rules, it and all answers that chain off of it will be deleted
• Don't edit your code after you've posted it, otherwise it could invalidate code that chains off of it

Winning

The winner of the challenge is whoever has posted the most recent answer, since it will get harder and harder the more languages that are used.

Answer 12

I'm sorry, Code Golf

code-golf ascii-art

This challenge is inspired by a series of Garfield-inspired artwork in which Garfield is depicted as a horror creature, stalking his owner, Jon. Commonly referred to as "Creepy Garfield", the line "I'm sorry, Jon" can be found in one of the earliest Creepy Garfield images, created by DubbleBaby.

William Burke's Depiction

After being used over and over again by the Code Golf community, our beloved Jimmy has transformed - no longer bound to his weak, mortal body. He has become the embodiment of spaghetti code, the ascii manifestation of hours-long debugging sessions.

---

Your Task:

Take 3 ordered numerical inputs and output Jimmy's body

Inputs

Input is received in the form x y z where:

x is the number of left limbs (integer between 1 & 10)
y is the number of right limbs (integer between 1 & 10)
z is the number of heads (integer between 1 & 10)

----Sample Input----
2 8 1

Meta Note: I don't think increasing the possible amount of body parts will influence the solutions but please let me know if you think they should be higher.

Body Parts

Head =          <o>
Left Limb =     /
Right Limb =    \
Filler Limb =   |
Body Piece =    0

Body Generation Rules

   1. Left limbs must be attached to the left side of a body piece
    (excl rule 3)
    - Correct:  /0
    - Incorrect: /<o>
    - Incorrect: 0/
    - Incorrect: /0\0\

2. Right limbs must be attached to the right side of a body piece
    (excl rule 3)
    - Correct: 0\
    - Incorrect: <o>\
    - Incorrect: \0

3. Limbs must not touch
    - Correct: /00\
    - Incorrect: /0\/0\

4. An external body piece without a limb must have a | in its place
    - Correct: /0|
    - Correct: |0|
    - Correct: /00\
    - Incorrect: /0
    - Incorrect: 0\

5. Heads must be between body pieces (horizontally not vertically)
    - Correct: 0<o>0
    - Incorrect: 0<o><o>0
    - Incorrect: 0<o>

6. All lines must be aligned centre
    - Correct:      /0\
                  /0<o>0|
                    /0\

    - Incorrect:    /0\
                    /0<o>0|
                    /0\

7. The bottom line of Jimmy's body must always contain a left and right limb
    - Correct:      /0\
                  /0<o>0|
                    /0\

    - Incorrect:    /0\
                  /0<o>0\
                    /0|

8. Jimmy's body must be whole and cannot be separated into sections
    - Correct:    /0\
                /0<o>0|

    - Incorrect:    /0\   /0\   |0<o>0|

    - Incorrect:      /0\

                    /0<o>0|

Examples

Input:
2 8 2

Sample Output:

/0<o>0<o>0\
    |0\
    |0\
    |0\
    |0\
    |0\
    |0\
    /0\

    OR

  /0\
  |0\
|0<o>0\
  |0\
  |0\
|0<o>0\
  |0\
  /0\

---

Rules & Win Conditions

1. You may receive the stated input via any method into a program or function.
2. You may display the output in any clear and discernible way.
3. Your output must obey all Body Generation Rules.
4. The previous 3 rules must be followed for all 1000 combinations of inputs.
5. Standard loophole rules apply.

As this is code-golf, least amount of code in bytes wins.

Answer 13

Minimum string attractors

code-golf string optimization

---

String attractors

Let \$S\$ be a string of length \$n\$. An attractor of \$S\$ is a subset of indices \$A \subset \{0, \ldots, n-1\}\$ such that every nonempty contiguous substring \$S[i \ldots j]\$ of \$S\$ has an occurrence \$S[i' \ldots j']\$ whose index set \$[i' \ldots j']\$ intersects \$A\$. A minimum attractor is one with minimal size. Minimum attractors can be used to implement very efficient string compression algorithms. In this challenge, your task is to find a minimum attractor for a given string.

Example

Consider the string acabaccabc. Using 0-based indexing, one of its attractors is \$A = \{2,3,5,8\}\$. This graphic shows the positions of \$A\$:

acabaccabc
  ^^ ^  ^

For example, the occurrence of the substring ac in the beginning doesn't intersect \$A\$, but there is another occurrence after the first b that does. It turns out that no attractor of size 3 exists for this string, so \$A\$ is a minimum attractor.

Specifications

Your input is a nonempty string of lowercase ASCII characters. Your output is a minimum attractor for this string, in any reasonable format. You can use either 0-based or 1-based indexing.

There may be several choices for the minimum attractor. In that case you may return any one of them, but only one.

The lowest byte count wins.

Test cases

These are 0-indexed and show one possible output.

a -> [0]
aaa -> [0]
ababab -> [0,1]
qgqqgq -> [1,2]
abcbacaa -> [1,3,5,6]
abcdefgh -> [0,1,2,3,4,5,6,7]
jejjeeje -> [2,3,5]
sttststt -> [1,5]
ykkkkvyk -> [0,2,5]
assassins -> [0,2,6,7]
acabaccabc -> [2,4,6,8]
ssssssjjjsjj -> [5,8]
hrhrhhrhhhrr -> [3,7,10]
fubuaabubuau -> [0,1,4,6,10]
jjaahajjhahaaahjjh -> [2,6,8,11,14]

Answer 14

Posted here

Answer 15

Check If A Binary Search Tree Is Balanced

Now posted on CodeGolf.StackExchange.com:

Write The Shortest Program To Check If A Binary Tree Is Balanced

Answer 16

Posted to PPCG. Thx for the votes!

Answer 17

Find the Lowest Common Ancestor of Two Nodes In A Binary Tree

Any two separate nodes in a binary tree have a common ancestor, which is the root of a binary tree. The lowest common ancestor(LCA) is thus defined as the node that is furthest from the root and that is the ancestor of the two nodes.

The following are binary trees and the lowest common ancestors of the some of their nodes.

The LCA of 13 and 15 is 14.

The LCA of 47 and 49 is 48.

The LCA of 4 and 45 is 40.

The LCA of 13 and 14 is 14.

Challenge

Write the shortest program possible that accepts as input the root of a binary tree and references to any two nodes in the binary tree. The program returns a reference to the LCA node of the two inputted nodes.

Restriction

The binary tree does not have nodes with parent field references in any form. You may not use parent field references in your program.

Input

The root of a binary tree and references to any two nodes in the binary tree. This may be in the form of a reference to the root object or even a list that is a valid representation of a binary tree.

Output

Returns a reference to the node that is the LCA of the two inputted nodes.

Definition of a Binary Tree

A tree is an object that contains a value and either two other trees or pointers to them.

The structure of the binary tree looks something like the following:

typedef struct T
{
   struct T *l;
   struct T *r;
   int v;
}T;

If using a list representation for a binary tree, it may look something like the following:

[root_value, left_node, right_node]

Answer 18

A Picture is Worth a Thousand Words

The average word is four characters/bytes long. So a picture, according to the old saying, is worth 4 kilobytes. But how complicated can that picture get?

Using any language or length of code you want, generate an image exactly 4,000 bytes in size with the highest possible entropy. You may use any standard image format. Your score will be the compression ratio when your image is compressed as a .zip file. For example, an image that compresses to 2,000 bytes will score 2, but if it expands to 4,100 bytes it will score 0.9756. Lowest score wins.

Answer 19

Black Hole Evaporation

Background: In empty space, occurring all the time, there are pairs of particles that appear and then, usually soon after, cancel each other out. At a certain distance from a Black Hole, it's possible that a pair of particles might spontaneously appear and, if the distance is just right, one of the particles will fall into the Event Horizon while the other escapes off into space, never getting a chance to cancel each other out. The exit of those particles is Hawking Radiation. Eventually, this process causes the entire Black Hole to evaporate away.

Challenge

Given a string of numbers, emit the negative of the single digit number closest to, in front of, the infinity symbol ∞ (the event horizon), and continue emiting it until there are no digits left in front of the infinity symbol. Then print the rest of the string masking each character uniquely and different from the masked character (burst of energy that might take place at the final instant), excluding any infinity symbols.

Test cases

Input:                      Output:
111∞4567                    -1 -1 -1 jkl;
3∞                          -3
3-145∞962                   -5 -4 1 -3 ™©®
4-567-9∞1-23                 9 -7 -6 5 -4 😐😈😎😻
2-1∞                        1 -2
34∞67∞89                    -4 -3 9876
-123∞456                    -3 -2 1 ♫♪#
6-6∞6                       6 -6 ä
48120∞                      0 (or -0) -2 -1 -8 -4
---5∞555                    5 オゼヰ

Challenge rules

• Anything after the first infinity symbol can be ignored as it has fallen into the Black Hole and we know nothing more about it anyway until after evaporation, where the information is a bit scrambled.
• The code should only expect numbers, negations, and infinity symbols. No decimal points or other symbols. The input can be an array, list, etc..., but each character must be separate, including the negation and infinity characters.
• A negation only applies to the single digit immediately after it. See the test cases above.
• You may mask the remaining characters after evaporation with any character set of your choice, as long as the resulting character is different from the masked character, and each character in the resulting output is unique. For languages limited to smaller character sets (or type constraints), characters may repeat after each possible unique character has already been utilized in the output.
• You may use the '_' symbol instead of the '∞' symbol.

General rules

• This is code-golf, so shortest code in bytes in its respective language wins.

• Standard rules apply for your answer with default I/O rules, so you are allowed to use STDIN (with the specification above)/STDOUT, functions/method with the proper parameters and return-type, full programs.

• Default Loopholes are forbidden.
• If possible, please add a link with a test for your code (TIO).

Answer 20

caN it be acrOnymised?

Answer 21

BotNets KotH

king-of-the-hill javascript grid

Controller, Example and Submission Template now added

---

flavor text not yet written

This is a web-based JS KotH where submissions have 2 parts, a Worker Bot and a Controller Bot. The goal is to have the most gold at the end of the game, by killing other bots and collecting gold found on the grid, while navigating the grid and surviving.

Worker Bots

A Worker Bot is a class(ES6 or ES5) based on this format:

class YourWorkerBot extends WorkerBot {
    performAction(message) {}
    sendMessage(x, y, surroundings) {}
}

Each botnet has 20 Worker Bots. For every botnet, its worker bots are

Method Descriptions:

• constructor(index): sets the color that the controller displays the bot as
• performAction(message): returns an action(described below).
• sendMessage(x,y,surroundings): x and y are zero-indexed coordinates. surroundings is a flat array of the 5x5 area around the bot. returns message(string) to send to controller bot

Actions

Each move is formatted as a 2 element list([action, param]) where action is a string

• Movement: formatted as ["move", square] where square is an integer that represents the square you want to move to, using the same index as the surroundings object. You can only move one square orthogonally or diagonally. Moving onto a square with a coin will collect the coin.
• Kill: formatted as ["kill", square] where square is an integer that represents the square you want to attack, using the same index as the surroundings object. You can only kill a bot one square orthogonally or diagonally. If you kill a square with no bot, you do nothing. You get half the coins(rounded down) of the bot you attacked.
• EMP: formatted as ["emp",undefined]. It causes all bots including itself in the 7x7 surrounding area can't move next turn. This costs 3 coins.
• Any invalid action is treated as you doing nothing.

Surroundings

The surroundings object will be a flat array of the 5x5 area around you, starting from the top left corner and going left to right and top to bottom. The grid below shows how the indexes of the array map to the actual grid area. Each square will be either a string, where "B" is a bot, "C" is a coin, "E" is an edge(not a valid move target) and "" is empty.

 0  1  2  3  4
 5  6  7  8  9
10 11 12 13 14
15 16 17 18 19
20 21 22 23 24

Controller Bot

A Controller Bot is a class(ES6 or ES5) that extends the following class:

class YourControllerBot extends ControllerBot{
    constructor(locations){
         super(locations)    
         this.storage=""
    }
    sendMessage(messages,index){
         return ""
    }
}

Each botnet has only 1 Controller Bot.

Method Descriptions

• constructor(locations): locations is an array of the initial locations([x,y]) of the worker bots.sets initial storage value
• sendMessage(messages,index): messages is a list of lists of the messages sent by all the worker bots(not just your own), always in the same order and grouped by botnet. returns message to its worker bots whose index is index.

The Game

The arena will be a 100x100 grid with 100 random coins scattered around it. Each game will have 1000 rounds and will have up to 15 randomly selected botnets. Every round, 10 coins will spawn at a random unoccupied spot. Every worker bot will get 1 turn per round. Each botnet's worker bots will perform an action in the same order for the entire game, but the order in which botnets take turns is randomized every round. Every turn, all the worker bots' sendMessage methods will be called(not just the worker bot taking the turn). After that, the controller bot's sendMessage method will be called. Finally, the worker bot's performAction method will be called and the action will be executed. This will repeat for every worker bot in a round.

Scoring

Each botnet's score is the sum of the coins collected by each of the worker bots. Botnets are ranked by most score.

Controller(WIP)

https://botnets-koth.firebaseapp.com

Example

function sampleBotnet() {
    class SampleControllerBot extends ControllerBot {
        constructor(locations) {
            super(locations);
            this.storage = "";
        }
        sendMessage(messages, index) {
            let surrondings = messages.find(message => message[0] === index)[1];
            let otherBot = surrondings.findIndex(
                (square, i) =>
                    square === "B" && [6, 7, 8, 11, 13, 16, 17, 18].includes(i)
            );
            if (otherBot !== -1) {
                return ["kill", otherBot];
            }
            let coin = surrondings.findIndex(
                (square, i) =>
                    square === "C" && [6, 7, 8, 11, 13, 16, 17, 18].includes(i)
            );
            if (coin !== -1) {
                return ["move", coin];
            }
            let validMoves = [6, 7, 8, 11, 13, 16, 17, 18].filter(
                x => surrondings[x] === ""
            );
            return [
                "move",
                validMoves[Math.floor(Math.random() * validMoves.length)]
            ];
        }
    }
    class SampleWorkerBot extends WorkerBot {
        performAction(message) {
            return message;
        }
        sendMessage(x, y, surroundings) {
            return [this.index, surroundings];
        }
    }
    return {
        name: "SampleBotnet",
        color: "red",
        controllerBot: SampleControllerBot,
        workerBot: SampleWorkerBot
    };
}

#Submission Template
```javascript
/* eslint constructor-super:0,no-this-before-super:0,no-unused-vars:0*/
import ControllerBot from "./src/scripts/ControllerBot.js";
import WorkerBot from "./src/scripts/WorkerBot.js";

//copy the part below
function yourBotnet() {
    class YourControllerBot extends ControllerBot {
        constructor(locations) {
            super(locations);
            this.storage = "";
        }
        sendMessage(messages, index) {
            return [];
        }
    }
    class YourWorkerBot extends WorkerBot {
        performAction(message) {}
        sendMessage(x, y, surroundings) {}
    }
    return {
        name: "YourBotnet",
        color: "",
        controllerBot: YourControllerBot,
        workerBot: YourWorkerBot
    };
}

Rules

• Standard Loopholes apply
• Bots cannot modify or add global variables
• Bots cannot call controller functions or other bots' methods
• Bots cannot read or modify other bots storage
• Bots may not access the internet
• I may disqualify any bot which does anything I deem to be cheating.

Sandbox

• Is the bar to entry too high?
• Can the current turn/round system be improved?
• Any better names for the 2 bots/title?
• Is there enough room for creativity?
• Would it be better if I merged the 2 classes into one class?
• Is there anything broken with the spec?

Answer 22

Up side down keyboard

Jono 2906 wants you to create a translator from plain Australian to up-side-down text after inventing a keyboard dedicated to typing up-side-down text, since they still want to demonstrate that their keyboard is powerful after failing to program in their keyboard.

However, they want your implementation to be typed with their own keyboard, since they also want to get used to programming using their keyboard.

Input/Output

The whole ASCII character set mapped to their up-side down variation (the up-side down " is a double ,):

 !"#$%&'()*+,-./
0123456789:;<=>?
@ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]^_
`abcdefghijklmno
pqrstuvwxyz{|}~

 ¡,,#$%⅋,)(*+'-˙/
0ƖᄅƐㄣϛ9ㄥ86:;>=<¿
@∀qƆpƎℲפHIſʞ˥WNO
ԀQɹS┴∩ΛMX⅄Z]\[^‾
,ɐqɔpǝɟƃɥᴉɾʞlɯuo
dbɹsʇnʌʍxʎz}|{~

The rest of the characters are kept as-is(yes, the unprintable characters are in the ASCII character set). The characters that are larger than 0x7f will be mapped back by subtracting the character code by 128.

If you are using a character that is larger than 256, modulo the character's character code by 128 before checking the availability.

Rules

• No standard loopholes, please.
• Input and output will be taken with our standard input methods.
• If you force Jono 2906 to change a key on their keyboard (allowing typing your specified character), you will get a penalty of +2 bytes for every key you add.

---

code-golf restricted-source string

Answer 23

Wrong position

I typr re;atively accuratrly, but so,etimes I made a whole nlock of text illegible by shifting a key right. So I need a program that corrects my text back to its original meaning.

Rules

• You have to left shift on a standard English QWERTY keyboard.
• Whitespace do not count for the procedure before left-shifting and are kept as-is in a standard left-shifting procedure. If the key is the leftmost letter/symbol on a keyboard(i.e. The ~key, Q key, A key, Z key.), the key is kept as-is. If you reach a control character while left-shifting (Caps lock and Shift), their effects will not be triggered and the character before left-shifting is kept.
• This is a code-golf contest; the shortest answer wins.
• Both the input and the output shall be given via our default methods.

Representation of a subset of the QWERTY keyboard that you will need

The two lines connected are possible values of the key: shifted/unshifted.

~!@#$%^&*()_+
`1234567890-=

QWERTYUIOP{}|
qwertyuiop[]\

ASDFGHJKL:"
asdfghjkl;'

ZXCVBNM<>?
zxcvbnm,./

(Space)
(Space)

Input

The input will always be a non-empty string conforming the rules above.

Output

The output will be the input string corrected to the originally intended meaning.

Examples:

Yjod ,sfr yjr, imjsppu/ -> This made them unhappy.
vpfr hp;g -> code golf

Feedback

I think this is not a duplicate; however, is any part of this challenge unclear or needs improvements?

---

code-golfstring

Answer 24

Path to Path Rearrangement

code-golfpermutationssequencefractal

In the xkcd comic "Map of the Internet", a special fractal path was used, similar to this:

0  1  14 15
3  2  13 12
4  7  8  11
5  6  9  10

Ascii art version:

-0---1  14---15--16 19--20---21
     |   |       |   |       |
 3---2  13---12 17---18 23---22
 |           |           |
 4   7---8   11 30---29 24---25
 |   |   |   |   |   |       |
 5---6   9---10 31  28--27---26
                 |
58---57 54---53 32  35--36---37
 |   |   |   |   |   |       |
59  56---55  52 33---34 39---38
 |           |           |
60---61 50---51 46---45 40---41
     |   |       |   |       |
63---62 49---+---47 44--43---42
\|/

This path, known as the Hilbert curve, has some interesting properties. Among other things, it can be flipped diagonally without changing most of those properties.

-0   3---4---5  58--59---60  63->
 |   |       |   |       |   |
 1---2   7---6  57---56 61---62
         |           | 
14---13  8---9  54---55 50---49
 |   |       |   |       |   |
15  12--11---10 53--52---51   48
 |                           |
16---17 30---31--32--33 46---47
     |   |           |   |
19---18 29---28 35---34 45---44
 |           |   |           |
20  23---24  27 36  39---40  43
 |   |   |   |   |   |   |   |
21---22 25---26 37---38 41---42

Your task is to apply this transformation. Given a space on one path, find the corresponding location on the other. For example, the fourth space in the top path is located at (0, 2), which is the 14th space along the second path, so the correct output for 4 is 14.

As with similar sequence challenges, this can be done as:

• An infinite sequence along the second path of the corresponding locations along the first path
• A function/program that takes a numbered position on the first path and returns the distance to that point on the second path.
• A function/program that takes a numbered position on the first path and returns all path 1 positions along path 2 to the point specified.

The first 64 terms of this sequence (zero indexed, add one to each for one indexed) are:

0 3 2 1 14 15 12 13 8 11 10 9 6 7 4 5 58 57 56 59 60 63 62 61 50 49 48 51 52 55 54 53 32 35 34 33 46 47 44 45 40 43 42 41 38 39 36 37 26 25 24 27 28 31 30 29 18 17 16 19 20 23 22 21

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

Meta Questions

• Do I need a better description of the paths?
• Is the challenge itself clear?
• Any other issues I should fix before posting?

Answer 25

Maximize the Hello, world's in code permutations

In this task you should output this exact string: hi orb (because Earth is a sphere). However, here is the catch: you must output as many hi orb's as possible in all of your code permutations. Identical permutations do not count(e.g. aa's permutations count as one permutation)

Say you have a program abc that outputs this string. You should try your best to make acb, bac, bca, cab, and cba (i.e. the permutations of abc) also output this exact string.

Rules

• No standard loopholes, please.
• Input/output must obey our standard methods.
• Your score is simply the factorial of the length of your code. You shall also present the following score: The score is counted in the negative of the length of your source code divided by the number of permutations that your code generates; (expression: -(source length/permutations).) Of course you want to keep your score as low as possible.
• All comment characters in your language are disallowed, in order to avoid collapsing into a radiation-hardening challenge.
• If you are using the filename as data, the filename must also count in the permutations.
• The source code length should be <1000. (Don't ask why, it's just an attempt of avoiding abusing the source code length.)

Feedback

• Is it detailed enough?
• Is the input/output rules clear enough?
• Do I need any more information?

I don't think this is a duplicate because nobody has asked a question tagged with both permutation and hello-world. However, I worry that this challenge will collapse into a radiation-hardening challenge if you comment out a single character and then make sure that this will produce the same result, therefore making it a flavored version of this question and close to a duplicate.

---

code-golfsource-layouthello-worldpermutations

Answer 26

The Celestial Bureaucracy king-of-the-hill

Posted

Answer 27

Creep Spread Territorial Control (WIP)

king-of-the-hill grid

javascript (probably)

---

Blah blah blah flavor blah blah blah something about Starcraft blah blah blah

Gameplay

Initial State

There is a 150x150 grid of square cells with approximately 7500 random cells missing in a symmetric Perlin noise pattern. There are four creep spread factions competing for dominance of this territory beginning as a single cell 10 cells in from a corner of the grid (one faction per corner). Each faction starts with 50 energy. The board does not wrap around at the edges.

Expansion

Each turn, each faction earns 1 point of energy for each controlled cell plus 20 base energy. This energy is used for expansion. How much a cell costs to expand to depends on how many cells controlled by the same faction are in the Moore neighborhood of the target cell.

• 0 neighbors: cannot expand to this cell
• 1 neighbor: 50 energy
• 2 neighbors: 20 energy
• 3 neighbors: 12 energy
• 4 neighbors: 8 energy
• 5 neighbors: 5 energy
• 6 neighbors: 3 energy
• 7 neighbors: 2 energy
• 8 neighbors: 1 energy

There is no limit to how many cells can be expanded to in one turn other than energy costs. All expansions occur simultaneously. If two or more factions attempt to claim the same cell on the same turn, the one with the most neighbors of its own faction will claim the cell. If there is a tie, none of the factions claim that cell. Players whose expansions failed due to competition will not be refunded. Factions may expand onto each other's territory, stealing ownership of the cell.

Game End

The game lasts 10,000 turns or until there is only one faction remaining, whichever happens first. The winner is the faction with the most owned cells. Ties are broken by remaining energy.

The overall winner will be resolved with a randomized pool where each bot plays an equal number of games followed by 12 games of the top 4 contenders. (one for each possible corner positioning)

Coding

Write a bot that plays this game

• Bots must be deterministic. As a way to provide localized pseudorandomness, a random integer between \$0\$ and \$2^{32}-1\$ will be passed to the bot, which will be seedable in the controller.
• Bots have perfect information of the current state of the board, which turn it is, and their own energy, but not the energy of other players.
• Bots may not remember anything between turns, but may initialize constants and utility functions at the beginning of each game.

The list of desired expansions is ordered. As soon as an invalid expansion target cell is encountered (whether by cost or lack of same-faction neighbors) in this list, the rest of the list will be ignored and a warning will be logged.

Answer 28

Turing-complete regex subset

cops-and-robbers regex code-golf restricted-source

It's widely known that a programming language is one iff it's capable of addition of natural numbers and primality testing. In practice, this criterion has a high accuracy for distinguishing Turing-complete languages too.^{[citation needed]}

Cops' challenge

Choose any of the programming languages available on tio.run. Write a regex that will define a subset of this programming language. The subset must still match the definition, though ideally this should be far from obvious.

Write two programs in this language that match this regex:

1. Take two natural numbers, a and b, as input. Output a + b. The program must work for 0 ≤ a + b < 215.
2. Take a natural number n as input. Output whether the number is prime. The program must work for 0 ≤ n < 215.

The behavior outside of this range is undefined. This means that you can output the correct answer, a cute cat ASCII art, an error, an invalid answer, invoke nasal demons, or anything else you can, or cannot, imagine.

Regex come in multiple flavors. Choose one. You can choose any flavor available on regex101, or Retina.

In your answer, include:

• the programming language and regex flavor you chose
• the regex delimiter and flags you chose (for example: //gm; does not apply to Retina)
• the regex you wrote and its byte count
• the byte counts of your two programs

Keep the programs hidden. If 7 days pass without anyone cracking your answer, you may reveal your two programs by editing them into your answer. This will make your answer safe. Your score then becomes your regex's bytecount (lower is better). Before your answer is safe, your score is positive infinity.

Robbers' challenge

Write two programs that prove the subset to be a valid programming language. The rules that apply here are the same that apply to the cops. Additionally, your programs must not exceed the cops' in length.

When you crack an answer, post your programs to the robbers' thread.

Meta questions

The above will be posted as the cops' thread, with the robbers' thread simply linking to it.

• Any improvements to challenge structure? I've never done this before.
• Do you see any loopholes that need addressing?
• Are the allowed regex flavors reasonable?
• Duplicates?

Answer 29

Calculate the Ultraradical code-golfnumber

Answer 30

Moved.