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

Here's a challenge I'd like post because I'm curious to see what people will come up with. It's a bit of an anti-code-golf question because the code should look normal.

Is it clear what the constraints? Did I miss anything?

---

Introduction

Write a piece of unsuspicious code that does the following:

Let's say you've written a parser that parses it's input line by line and somewhere in your code is

find_string(line, "[start]", "[end]") // returns string between [start] and [end]

This program, when given it's own source code plain text as input, will match that line (twice actually); but we don't want that. It should still parse what it was designed for but not match any line of it's own source code.

Rules

• It's preferred that your code makes it obvious that one of it's intended uses is to parse (and not match) itself. This is so anyone 'refactoring' the code will not accidentally undo the trick that made it work.
• Your source code as input will be reduced to a single line.
• Your program should be able to handle large input (~10mb) and perform reasonably (for your chosen language).
• Your program does not need to parse the input line by line but that just seems like something reasonable code would do.
• Points are awarded for code that looks like a normal parser and contains as little assumptions about the input as possible. Bonus points for solutions that contain the start and end delimiters in that order.

Easy solutions are to swap the start and end token arguments or to pre-treat the tokens in some way but that would look suspicious. Someone will come along and refactor your code and break the 'trick'.

I'm interested in reasonable solutions because this is a reduction of a real life problem.

Example Input and Output

• Input lines may or may not contain [start] or [end], only return it in the output when it occurs in a pair.
• Input lines will never contain more than one pair of [start] and [end] tokens.
• Input lines may contain additional content before [start] or after [end]
• Your source code plain text will be inserted at a random line in the input.

Input #1:

[start]hello[end]
<<your source code plain text>>
dont output this[start]world[end]

Output #1:

hello world

Input #2:

lorem[start]i solemnly[end]
[start]false start
[start]swear[end]
ope, sorry just passing through
this is not the[end]
[start]that i'm up to[end]ipsum
[start]no[end]dolor
<<your source code plain text>>
[start]good[end]

Output #2:

i solemnly swear that i'm up to no good

Answer 2

Title: Transposition

** The challenge **

Given a set of notes (as a string, or a list, or any other reasonable input - but as letters and accidentals, not a numerical equivalent), the key those notes are in, and a target key; output the notes transposed into the new key. Some of the notes may not exist in the scale for the given key (e.g Eb in the key of C).

** Inputs **

The complete set of input notes for this challenge will use the English naming convention, and so are as follows:

Ab,G##,A,A#,Bb,B,C,C#,Db,C##,D,D#,Eb,E,F,F#,Gb,F##,G,G#

where "b" represents a flattened note (down one semitone per b), and # represents a sharpened note (up one semitone per #). Theoretically all notes can be extended further with more #s and bs; but for the purposes of this program that won't happen beyond what is already given.

** What is transposing? **

Transposing a song involves "moving" the song into a different key, by finding the equivalent note of the scale in that key.

We will assume Major scales for the purposes of this challenge.

** Scales **

The scales for this challenge are officially as follows:

• C: C, D, E, F, G, A, B, C
• C#: C#, D#, E#, F#, G#, A#, B#, C#
• Db: Db, Eb, F, Gb, Ab, Bb, C, Db
• D: D, E, F#, G, A, B, C#, D
• D#: D#, E#, F##, G#, A#, B#, C##, D#
• Eb:Eb, F, G, Ab, Bb, C, D, Eb
• E: E, F#, G#, A, B, C#, D#, E
• F: F, G, A, Bb, C, D, E, F
• F#: F#, G#, A#, B, C#, D#, E#, F#
• Gb: Gb, Ab, Bb, Cb, Db, Eb, F, Gb
• G: G, A, B, C, D, E, F#, G
• G#: G#, A#, B#, C#, D#, E#, F##, G#
• Ab: Ab, Bb, C, Db, Eb, F, G, Ab
• A: A, B, C#, D, E, F#, G#, A
• A#: A#, B#, C##, D#, E#, F##, G##, A#
• Bb: Bb, C, D, Eb, F, G, A, Bb
• B: B, C#, D#, E, F#, G#, A#, B

For simplicity, we can assume that both notes in the pairs A#/Bb, C#/Db, D#/Eb, F#/Gb, G#/Ab, C##/D, F##/G, G##/A are enharmonically equivalent (i.e. interchangeable - although they're not, always).

For scales with double-sharps, I will accept the enharmonic equivalents as an alternative implementation:

• D#: D#, E#, G, G#, A#, B#, D, D#
• G#: G#, A#, B#, C#, D#, E#, G, G#
• A#: A#, B#, D, D#, E#, G, A, A#

but for all other notes in the scale, they must match. If the note isn't in the scale, either can be used.

e.g.

• F in the key of C should transpose to F# in the key of C#, and not to Gb, because that option in the pair is explicitly in the scale
• but D in the key of C# could transpose to either C# or Db in the key of C, because it's an incidental anyway and so there's no easy rule to determine which it should be.

BONUS feel-good points *: normally it's # if you're going up, and a b if you're going down - feel free to implement this if you want!

For double-sharps (e.g F##) in all cases, It's OK if the program "resolves" these (e.g.to G in that case) even if they are in the scale; but again, some BONUS feel-good points * if you keep the double-sharps in.

Examples

• CDEFGABC in C to A -> ABC#DEF#G#A
• C# in C to A -> A# OR Bb
• ABCDEFGBAF#Bb in Bb to Gb -> FGAbBbCDbEbGFDGb
• CCGGAAAAGFFEEDDCGGGFFEEEDCGGGFFFFEEED in C to G# -> G#G#D#D#E#E#E#E#D#C#C#B#B#A#A#G#D#D#D#C#C#B#B#B#A#G#D#D#D#C#C#C#C#B#B#B#A#

Websites like http://www.logue.net/xp/ can be used to test your answers to other inputs

* Bonus feel-good points don't get you anything extra, unless someone can come up with a quantifiable difference that it should make to the score?

Answer 3

Interpret Unneccesary (Not quite)

Unneccesary is a joke language created by Keymaker. The source is unneccesary, and if given, it will error out.

Your task here is similar. If there is input, your program should error out. If the input is empty, your program should do nothing and terminate.

Answer 4

Mirror, Mirror, on the wall. Who's the fairest of them all?

Well, you know it's Snow White, and the evil Queen is at it again. Will Snow White be saved? Will she fall asleep once again? Will the Prince find her?

Challenge:

Given an arbitrary number (>= 2) of possibly duplicated hexadecimal color values (ranging from #000000 to #FFFFFF) and paired strings, calculate the following:

• If #FF0800 (Candy apple red) appears in the input, return "Return to Sleeping Death"
• If #000000 appears in the input, return "Saved by Grumpy"
• If #A98AC7 or #111111 appears in the input, return "Saved by Happy"
• If #21E88E or #222222 appears in the input, return "Saved by Sleepy"
• If #32DCD5 or #333333 appears in the input, return "Saved by Bashful"
• If #43D11C or #444444 appears in the input, return "Saved by Sneezy"
• If #54C563 or #555555 appears in the input, return "Saved by Dopey"
• If #65B9AA or #666666 appears in the input, return "Saved by Doc"
• If #76ADF1 or #777777 appears in the input, return "Saved by the Seven Dwarfs"
• If #FFFAFA (Snow) appears in the input, return "Saved by Love's first kiss"
• If an F variant appears in the input, return "Press F to pay respects to Snow White"
  • An F variant is any number that contains at least one F in its hexadecimal form, and is otherwise all 0s (e.g. #0FF0F0, #FFFFFF, #00000F, #F00F00)
• If multiple of the preceding occur, return the "fairest" answer. The "fairest" answer is calculated as follows:
  • For all N occurrences of special color values, choose the (N-1)/2-th (truncating division) occurrence. The associated special output is the "fairest" answer.

"Appears in the input" here refers to only the hexadecimal color values, and not to the paired strings.

• If none of the preceding occur, return the "fairest" answer. The "fairest" answer is calculated as follows:
  • Take the hexadecimal color value at the end of input values, write it down, and exclude that single color-string pair from consideration as the "fairest" answer
  • Show its binary form to the mirror, computing a reflection of only the last 24 (#FFFFFF is the mask) bits.
  • Choose the hexadecimal color with least Hamming distance from the reflection. If there are multiple (N) such colors, choose the middle ((N-1)/2-th, truncating division) instance of the color. The "fairest" answer is the associated string for the color.

Inputs:

A sequence of hexadecimal color values and String values separated by a space. The input may also be read as two separate sequences of hexadecimal color values and String values, or a single sequence of 2-tuples (either (hexValue, stringValue) or (stringValue, hexValue) is permissible, as long as the ordering is consistent across all 2-tuples). Input order matters - for each index, the corresponding element in the supply of color values is "associated" with the corresponding element in the supply of String values, and duplicates can affect the "fairest" answer. The effect is something like Function(List(HexColorValue),List(AssociatedStrings)) -> "fairest" answer. Hexadecimal color values may be represented as either (your choice of) a String "#"+6 digits, or 6 digits alone, as long as the representation is consistent across all color values.

Here's an example input:

76ADF1 Return to Sleeping Death
2FE84E Return whence ye came!

Here's another example input:

2FE84E Return to Sender
4FFAFC Return of the Obra Dinn
2FE84E Return to the house immediately, young lady!
2FE84E Return to Sleeping Death
2FE84E Return of the Jedi

Here's the third example input:

2FE84E Return to Sender
4FFAFC Return of the Obra Dinn
2FE84E Return to the house immediately, young lady!
2FE84E Return to Sleeping Death
7217F8 Return of the King

Here's the final sample input:

F4A52F Eating hearts and livers
F4A52F Eating apples
F4A52F Eating porridge
F4A52F Eating candy houses
F4A52F A Modest Proposal

Outputs:

The "fairest" answer as computed by the specified logic. For example, on the first sample input, the "fairest" answer would be Saved by the Seven Dwarfs, due to the special hex color 76ADF1 appearing within the input.

In the second sample, there are no special inputs. First, we take "2FE84E Return of the Jedi", which has value #2FE84E. In binary, this is:

001011111110100001001110

We take the reflection from the mirror, getting:

011100100001011111110100

We compare it against 2FE84E (001011111110100001001110) and 4FFAFC (010011111111101011111100), which have Hamming distances of 18 and 12 from the reflection, respectively. Since #4FFAFC has the uniquely lowest Hamming distance from the reflection, the "fairest" answer is Return of the Obra Dinn.

In the third sample input, there are no special inputs. First, we take "7217F8 Return of the King", which has value #7217F8. In binary, this is:

011100100001011111111000

We take the reflection from the mirror, getting:

000111111110100001001110

We compare it against 2FE84E (001011111110100001001110) and 4FFAFC (010011111111101011111100), which have Hamming distances of 2 and 8 from the reflection, respectively. All 3 instances of hexadecimal color value #2FE84E have minimum Hamming distance from the reflection, so we take the (3-1)/2=1th instance (0-indexed) of #2FE84E. Therefore, the "fairest" answer is Return to the house immediately, young lady!.

In the last sample input, there are no special inputs. First, we take "F4A52F A Modest Proposal", which has value #F4A52F. In binary, this is:

1111010011001100101111

We take the reflection from the mirror, getting:

1111010011001100101111

We compare it against F4A52F (1111010011001100101111), which has Hamming distance 0 from the reflection. All instances of hexadecimal color value #F4A52F have minimum Hamming distance from the reflection. There are FOUR instances of #F4A52F, because we always exclude the last hexadecimal color instance from evaluation. Therefore, we take the (4-1)/2=1th instance (0-indexed) of #F4A52F, and the "fairest" answer is Eating apples. If you don't exclude the last value from consideration, you actually get the (5-1)/2=2th instance of #F4A52F (Eating porridge), which is wrong.

Rules:

• No standard loopholes
• Input/output taken via standard input/output methods.
• The output must be exactly equal to the "fairest" answer

Scoring:

This is code golf, so shortest program wins.

_{Posted~ you can see it here}

Answer 5

CMC: Cross-Multiplication Calculator code-golf math arithmetic

In this task you should create a Cross-Multiplication Calculator.

---

Cross-multiplication is a way of factoring an algebraic expression. This is the expression form that this way can solve:

$$x^2 + ax + b$$

\$a\$ and \$b\$ are constants here, and \$x\$ is a variable.

^{Anyway, as far as I can tell, this expression form is only solvable in this method.}

Anyway, how do I do Cross-Multiplication? (TODO)

You first take the number \$b\$ and factor this number into integral factors.

Okay. We are using the expression \$x^2 + 8x + 16\$ as an example.

(Although 16 is not a prime) let us assume that 16 only has 2 possible factors:

• \$-1 \times -16\$ (because \$-x \times -x = x^2\$)
• \$1 \times 16\$ (Obviously this is 16)
• And the above 2 with the factors reversed.

Now you sum these possible two factors and check this against the number \$a\$.

• Check 1. So \$-1 + (-16) = -17\$. And unfortunately -17 is not 8, we proceed to the next check.
• Check 2. So \$1 + 16 = 17\$. And unfortunately 17 is not 8, we proceed to the next check. There are no checks left.

Did I make a mistake? Of course, I need to change the factors.

• \$-2 \times -8\$ (because \$-x \times -x = x^2\$)
• \$2 \times 8\$ (Obviously this is 16)
• And the above 2 with the factors reversed.

We sum those values, and they are -10 and 10 respectively. So I should change the factors to another value:

• \$-4 \times -4\$ (because \$-x \times -x = x\$)
• \$4 \times 4\$ (Obviously this is 16)
• And the above 2 with the factors reversed.

Finally! \$4+4 = 8\$, and here is the factorization:

$$(x+4)(x+4)$$

^{Now you will probably realize why I desperately need a program to automate this.}

Test cases

You can assume that the input is always valid. You do not have to specify the variables, only the numbers. Therefore the expression

$$x^2 + ax + b$$

is converted into:

$$+a \, +b$$

The expected output is not:

$$(x+\alpha)(x+\beta)$$

but:

$$+\alpha \, +\beta$$

a, b => α, β
8, 16 => 4, 4
-5, -24 => 3, -8

Scoring

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

Meta

• Is this clear enough?
• I haven't found a duplicate, but anything? (Although unlikely, I found nothing by searching "Cross Multiplication".)
• Tags are code-golf, string and interpreter. Anything else?
• Any further feedback?

Answer 6

Parse a regex

Grep is a wonderful tool. It can find stuff in files, it can help you spell stuff correctly (grep 'whatever' /usr/share/dict/words or wherever that file is), and it can even test if something is a prime number!

However, the first version was implemented back in the golden age, when FORTRAN was respected, Pascal was the language for beginners, and object orientation was just starting out in on its great adventure.

One could argue that modern developers have nowhere near that much talent or skill, what with their flashy "IDEs" and "frameworks". If they would be asked to implement something similar, they would just jump at the nearest library or cloud thingimabob and say "Done!".

At least, that is what some would say.

Prove them wrong! Golf grep!

Parse a regular expression without calling any built-in functions or operators explicitly meant for this.

input:

Basically the same as a simple grep: a regular expression as a command line parameter, followed by an optional filename or a dash. If the filename is not present, or it is a dash, read for stdin.

This is the recommended way to do it, but if you can write an adapter (eg: post stuff to a php form for your program via a shell script), then that is OK as well. The adapter does not contribute to your score.

output

Lines that match the regular expression.

Notes:

The regex dialect is PCRE (perl compatible). Files use unix line terminators if it is relevant.

Answer 7

Predict the state of a Minecraft inventory after click events

Minecraft does inventory management over the network by sending packets describing the clicks that a player does. If you're caching these events, it can be non-trivial to predict what state the inventory is in after the clicks

Challenge

Take an inventory of 9 slots, each with an item and a type. Assume all items can stack up to 64 and that if a slot would be "overfilled" that the cursor will continue holding onto the items. Then, take a list of the slot index, button, and mode variables for the clicks to be done (mode and button are defined at https://wiki.vg/Protocol#Click_Window). Output the inventory afterwards.

Restrictions/Rules

You may input and output the inventory in any reasonable format. You may take click input in any reasonable format. You may ignore Mode==2, as the player inventory is not implemented correctly enough for this. You may ignore Mode==3 because this is a survival player You may ignore Mode==5 where Button==8, 9, or 10 for the same reason as Mode 3. Dropping the item is a delete. Your player won't pick it back up or anything silly like that. You may assume that input will have valid counts Don't use standard loopholes

Examples

Input:

[["diamond",64],[],[],[],[],[],[],[],[]]

[
 [0, 0, 0]
 [0, 0, 1]
]

Output

[[],["diamond",64],[],[],[],[],[],[],[]]

Input:

[["diamond",64],["dirt", 64],[],[],[],[],[],[],[]]

[
 [0, 0, 0]
 [0, 0, 1]
 [0, 0, 2]
]

Output

[[],["diamond",64],["dirt",64],[],[],[],[],[],[]]

Input:

[["diamond",64],[],[],[],[],[],[],[],[]]

[
 [0, 0, 0],
 [-999, 4, 4],
 [0, 4, 5],
 [1, 4, 5],
 [2, 4, 5],
 [3, 4, 5],
 [4, 4, 5],
 [5, 4, 5],
 [6, 4, 5],
 [7, 4, 5],
 [8, 4, 5],
 [-999, 4, 6],
 [8, 0, 0]
]

Output

[["diamond",56],["diamond",1],["diamond",1],["diamond",1],["diamond",1],["diamond",1],["diamond",1],["diamond",1],["diamond",1]]

Meta

I have no clue what I'm doing writing a question.

Tagged code golf

Critique goals:

• Improve testcases
• Improve description of problem
• Determine if the problem is too complex

Answer 8

A very-very old (maybe early 2000s) problem:

Print out a decimal number \$n\$ such as \$n^2\$ ends with \$n\$ with maximal length your program can compute in 60 seconds

In other words it's needed to find some long enough \$n\$ such as \$10^{\lfloor\log_{10}n\rfloor+1}|(n^2-n)\$.
A hint may be that an \$n\$ ending with \$5\$ is more easy to compute than an \$n\$ ending with \$6\$.

code-challenge

Answer 9

JavaScript: Free for All

king-of-the-hilljavascript

This is a very experimental idea of mine: given a function which is provided a single function as an argument, try to run that function the most times possible in a browser environment while competing against other bots.

Bot submissions

Each bot consists of a function. This function takes a scoring function as input. Each bot has a state consisting of three values:

• score: Number indicating score, winning criterion
• locked: Boolean which, when true, prevents further score increases
• calls: Number of times scoring function called in last 100ms (?), will set locked to true for the remainder of the round if it exceeds a certain value

The scoring function increments score and calls, as long as locked is not true.

Restrictions

If any of these restrictions are violated, a bot will have locked set to true.

No bot or bot-defined function may:

• Run longer than 5ms
• Attempt to modify the window location (location.href, location.assign, etc.)
• Attempt to connect to the internet (AJAX, WebSockets, etc.)
• Create web workers
• Affect hardware (sound, microphone, camera, USB, gamepads, etc.)
• Download files
• Leave an impact which cannot be fixed by reloading the page

Notes

This is almost certainly a very bad idea on an assortment of levels. If you have any suggestions of restrictions or ways to make the challenge more interesting, be sure to comment.

I'm considering some sort of system to determine which bot runs first that adds to the strategy, and interesting attack angles for other bots.

To prevent this from becoming a "read the last answer and exactly cancel out its strategy" type thing, I'm open to any suggestions.

Answer 10

Given a digit as an English word, output its numerical value.

For example, given the input one, you should output 1 (optionally with a trailing newline).

Your program should cover all the following cases:

zero  => 0
one   => 1
two   => 2
three => 3
four  => 4
five  => 5
six   => 6
seven => 7
eight => 8
nine  => 9

code-golf

Answer 11

Introduction

This challenge was inspired by the 24 Game.

In the 24 Game, you are given 4 numbers and are asked to make 24 using addition, subtraction, multiplication, division, and parentheses. So...

What is the biggest number you can make given 4 numbers using the above operations?

Challenge

For four given inputs a, b, c, d, output the biggest number you can get using addition, subtraction, multiplication, division, and parentheses.

This is code-golf, so the shortest answer wins.

Example Input and Output

  Input  -->  Output  -->   Explanation
 1,3,2,4 -->    36    --> (1 + 2) × 3 × 4
 5,5,5,5 -->   625    -->  5 × 5 × 5 × 5
 9,2,3,1 -->    81    --> (1 + 2) × 3 × 9
 

---

Please give feedback on this challenge and correct me if my outputs are wrong. Should I change it to the smallest number?

Answer 12

How many ACus do I have?

Posted to main

Answer 13

Make a Decompiler Bomb

Similar to the Make a Compiler Bomb challenge, but backwards.

The goal is to create the a 1KiB (1024 bytes) or smaller bytecode file that creates the largest output when decompiled.

Constraints

• A binary is either an x86 binary (in the form of an ELF file, PE file (.dll/.exe), or Mach-O binary) or a virtual bytecode file (e.g. Python .pyc, Java .class, .NET CLR, etc.)

• The decompiler can be any public (preferably free) decompiler of your choice. (e.g Snowman/Hex-Rays for x86 binarys, CFR/Fernflower/etc. for java, dotPeek for .NET, uncompyle6 for Python, etc.)

• A decompiler is any tool that takes a binary and attempts to reconstruct human readable source code from it.

• The largest output byte count wins, with the smallest input size as a tie-breaker

• The binary must be executable, and print "Hello World!"

• The decompiled code must be syntactically correct

Answer 14

I delete the input, you delete the source code

file-systemcode-golfstring

This is a new twist on the long running series on CGCC.

Your task, if you accept it, is to write a program/function that outputs/returns the contents of an input file. The tricky part is that if I delete the input file, your program must delete itself.

Rules

• The source code file and the input file should be in the same directory.

• The input file and source file can be named anything at all. I.e. The file names are your choice.

• The contents of the input file will be restricted to printable ASCII.

• The input file and the source file must be deletable.

• This is code-golf, so the shortest (original) code in each language wins!

• Default Loopholes apply.

Example

If your program is jspwjxnlow8229 and the input file exists, the program must print the contents of the file. If the file doesn't exist, the program must delete itself.

Feedback

In regards to file manipulation, have I specified the rules enough?

Answer 15

How healthy are my children?

As anyone who has twins will know, it can be hard to keep track of which child fed / was changed, and when.

That's why I've devised a system using OneNote on my phone. It's quick and easy to use.

Each entry (line) uses the following structure (note: I'm not a regex expert and the expression is more permissive than I want - see words for detail):

(ddMMyyyy )?HHmm ((1|2|B) (💧|💩|🤱){1,3}){1,3}

Or, in words:

1. For the first entry on or after midnight each day only, each line starts with the date.
2. The next component is always the time, hour and minute in 24 hour clock format
3. Next is a child identifier character - 1 or 2; or B if what follows applies to both children. All subsequent emoticons apply to the identified child, until a new child identifier is found or a newline. There is guaranteed to be at least one child identifier in a record.
4. Next comes any or all of the three emoticons (maximum one of each) representing a wet nappy (💧), a dirty nappy (💩) or a feed (🤱)
5. Repeat from step 3. until done. BUT - each emoticon will only appear once per child - so if it appears in B then it won't appear in either 1 or 2; and if it appears in either 1 or 2 it won't appear in B. It won't appear in both 1 and 2 (because then it would be in B instead). The regex doesn't show this subtlety.

Some other notes:

• Breast-Feeding (feed) emoticon 🤱 is codepoint U+1F931
• Droplet (wet) emoticon 💧 is codepoint U+1F4A7
• Pile of Poo (dirty) emoticon 💩 is codepoint U+1F4A9
• All items in the string are space-separated
• I would actually use the initials of my children's names, rather than 1 and 2 - but for the challenge I went with the numbers instead.

Example

02022020 0005 1 💩 B 💧 🤱
0230 2 💧 🤱
0250 1 💧 💩 🤱
0330 2 🤱
0400 1 🤱
0700 B 💧 🤱
0900 2 🤱
1000 2 💧 🤱
1020 1 💧 🤱
1220 1 🤱
1420 B 💧 1 💩 2 🤱
1440 1 🤱
1600 2 💧 💩
1700 1 💧
1745 B 🤱
2100 B 💧 🤱 1 💩
2350 2 🤱 B 💩 1 💧
03022020 0015 1 🤱 B 💧
0500 1 💧 🤱
0830 1 💧 🤱
0900 2 💧 🤱
1115 B 💧 1 💩
1215 B 🤱
1330 B 🤱
1400 2 💧 💩

The Challenge

Given the raw data, input as a single string or array of entries, containing data such as the above example, output a summary of:

• number of feeds, wet and dirty nappies, per baby, over the past 24 hours

"The past 24 hours" can be either based on system time, or the current time can be passed as an extra input.

The output format is up to you, as long as it:

a) is consistent across all runs of the program
b) shows the information required

some example outputs for the above inputs, with a current time of 14:30 on 3rd of February 2020 (hand-calculated, sorry if they're not right!):

Baby 1 had 6 wet nappies, 2 dirty nappies, and fed 8 times Baby 2 had 6 wet nappies, 3 dirty nappies and fed 6 times

{{6,6},{2,3},{8,6}}

{6,2,8},{6,3,6}

etc.

This is code-golf so lowest bytes wins. Usual exclusions apply.

Answer 16

I want to ask a combined popularity / objectively scored question. Something like:

Take a string as input. Match the string to a famous painting such as "Mona Lisa" and render a cartoon version of it. 1 point per painting, 1 point per upvote. Voting closes on XX/YY/ZZZZ.

I want to reward people for including more possibilities (there will be a fixed upper limit, unlike with paintings). I also want to reward people for the quality of their renderings. The cartoon paintings should be recognisable as versions of the real paintings.

Is this a good scoring system? If not, what would be better?

Answer 17

Implement PSL(2,3)

Since challenge to implement Galois field already have been many, I'm writing a challenge involving a group of Lie type!

Objective

Implement the multiplication and inversion in \$\text{PSL}(2,3)\$.

The ring \$\mathbb{Z}_3\$

The ring \$\mathbb{Z}_3\$ is the set \$\{0,1,2\}\$ with addition, negation, subtraction, and multiplication defined as modular arithmetic:

• Addition is the usual addition with the result moduloed by 3;

• Negation, subtraction, and multiplication are also analogously defined.

Reciprocal and division is also well-defined, but that's just another detail.

The group \$\text{SL}(2,3)\$

The multiplicative group \$\text{SL}(2,3)\$ is the set of 2-by-2 matrices whose entries are members of \$\mathbb{Z}_3\$ and the determinant is \$1\$. Note that the determinant is calculated using modular arithmetic. Matrix multiplication and matrix inversion is defined as:

• Matrix multiplication is the usual matrix multiplication, where addition and multiplication of the entries are modular;

• Matrix inversion of \$\begin{pmatrix} a & b \\ c & d \end{pmatrix}\$ is \$\begin{pmatrix} d & -b \\ -c & a \end{pmatrix}\$. This exploits that the determinant is \$1\$.

As a consequence, the elements of \$\text{SL}(2,3)\$ are:

$$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 0 & 2\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} $$

The factor group \$\text{PSL}(2,3)\$

\$\text{PSL}(2,3)\$ is defined as cosets of \$\text{SL}(2,3)\$ by \$\{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}\$. That is, elementwise multiplications of \$\{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}\$. They are: $$ \{\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 0\end{pmatrix}\}, \{\begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 2\end{pmatrix}\}, \{\begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 0 & 2 \\ 1 & 1\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 1 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 2 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 0 \\ 2 & 1\end{pmatrix}, \begin{pmatrix} 2 & 0 \\ 1 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix}\}, \{\begin{pmatrix} 1 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 2 & 2 \\ 1 & 0\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 0 & 2\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 2 & 0\end{pmatrix}\}, \{\begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}, \begin{pmatrix} 2 & 1 \\ 1 & 1\end{pmatrix}\}, $$

You pick an element of each coset as representives, and don't care about the rest.

Multiplication/inversion of such representives is defined as multiplication/inversion in \$\text{SL}(2,3)\$, then taking the representive of the coset the multiplication/inversion is in. For example, \$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}^2 = \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\$, if \$\begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}\$ and \$\begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\$ are representives.

Examples

Picking the left elements as representives of the cosets above: $$ \begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}^2 = \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}, \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}^2 = \begin{pmatrix} 1 & 2 \\ 1 & 0\end{pmatrix}, \begin{pmatrix} 1 & 0 \\ 0 & 1\end{pmatrix}\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} = \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}\begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} = \begin{pmatrix} 0 & 1 \\ 2 & 0\end{pmatrix}, \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix}^{-1} = \begin{pmatrix} 1 & 2 \\ 2 & 2\end{pmatrix} $$ To be more specific about the method of evaluation: $$ \begin{pmatrix} 0 & 1 \\ 2 & 1\end{pmatrix}\begin{pmatrix} 0 & 1 \\ 2 & 2\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 4\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} ≡ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}, \\ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix}^{-1} ≡ \begin{pmatrix} 2 & -1 \\ -1 & 1\end{pmatrix} ≡ \begin{pmatrix} 2 & 2 \\ 2 & 1\end{pmatrix} ≡ \begin{pmatrix} 1 & 1 \\ 1 & 2\end{pmatrix} $$ The steps of this algorithm is:

1. Do usual matrix multiplication/inversion;
2. Modulo the entries by 3;
3. Take the representive of the coset.

Though you can make any possible algorithm.

Rules

• Input type and format doesn't matter, but it must be a container of integers. In C, int[2][2] and int[4] are valid examples. This restriction prevents abusing the fact that \$\text{PSL}(2,3) \cong A_4\$.
• Output type and format doesn't matter either, but it must be the same as the input type and format.
• Invalid inputs fall in don't care situation.
• Multiplication and inversion may be in separate codes. In this case, the score is the sum of their lengths in bytes.
• Since this is a code-golf, the code with least score wins.

Answer 18

Very rough outline of a challenge that rewards short programs that take a long time.

Probably a no input and output can be anything except an error challenge.

Is there a nice way to exclude things like sleep(), wait() etc?

Would be required for 1 person to run all the programs for the timing to be fair.

Thinking that answers would include loops, recursion, testing of complex criteria.

Answer 19

Numbers by index

Challenge

Print the numbers:

0
1
22
333
4444
55555
666666
7777777
88888888
999999999

In that order.

I/O

Takes no input. The numbers can have any delimiters desired (or none). Example outputs:

0122333444455555666666777777788888888999999999

[0,1,22,333,4444,55555,666666,7777777,88888888,999999999]

etc....

Code Example

This is an un-golfed example that may perhaps act as algorithm guide (or maybe not):

Turing Machine Code, 553 bytes

0 * 0 r K
K * _ r 1
1 * 1 r L
L * _ r 2
2 * 2 r a
a * 2 r M
M * _ r 3
3 * 3 r b
b * 3 r c
c * 3 r N
N * _ r 4
4 * 4 r d
d * 4 r e
e * 4 r f
f * 4 r O
O * _ r 5
5 * 5 r g
g * 5 r h
h * 5 r i 
i * 5 r j
j * 5 r P
P * _ r 6
6 * 6 r k
k * 6 r l
l * 6 r m
m * 6 r n
n * 6 r o
o * 6 r Q
Q * _ r 7
7 * 7 r p
p * 7 r q
q * 7 r r
r * 7 r s
s * 7 r t
t * 7 r u
u * 7 r R
R * _ r 8
8 * 8 r v
v * 8 r w
w * 8 r x
x * 8 r y
y * 8 r z
z * 8 r A
A * 8 r B
B * 8 r S
S * _ r 9
9 * 9 r C
C * 9 r D
D * 9 r E
E * 9 r F
F * 9 r G
G * 9 r H
H * 9 r I
I * 9 r J
J * 9 r halt

Try it online!

This prints out the numbers with a space delimiter:

0 1 22 333 4444 55555 666666 7777777 88888888 999999999

Challenge Type

code-golf, so shortest answer in bytes (by language) wins.

Edit: Link to the related challenge. Curiously, there is one answer on there where if it was by index, and the zero was included, it would be shorter.

Answer 20

A malbolge interpreter

The challenge today is to write a Malbolge interpreter.

Specification

Malbolge
'98, Ben Olmstead

I hereby relenquish any and all copyright on this language,
documentation, and interpreter; Malbolge is officially public domain.

------------------------------------------------------------------------

                                Malbolge
                           '98, Ben Olmstead

Introduction
^^^^^^^^^^^^

It was noticed that, in the field of esoteric programming languages,
there was a particular and surprising void: no programming language
known to the author was specifically designed to be difficult to program
in.

Certainly, there were languages which were difficult to write in, and
far more were difficult to read (see: Befunge, False, TWDL, RUBE...).
But even INTERCAL and BrainF***, the two kings of mental torment, were
designed with other goals: INTERCAL to have nothing in common with any
major programming language, and BrainF*** to be a very tiny, yet still
Turing-complete, language.

INTERCAL's constructs are certainly tortuous, but they are all too
flexible; you can, for instance, quite easily assign any number to a
variable with a single statement.

BrainF*** is lacking the flexibility which is INTERCAL's major weakness,
but it fails in that its constructs are far, far too intuitive.
Certainly, there are only 8 instructions, none of which take any
arguments--but it is quite easy to determine how to use those
instructions.  Subtract 8 from the current number?  With a simple
'--------' you are done!  This kind of simple answer was unacceptable to
the author.

Hence the author created Malbolge.  It borrows from machine, BrainF***,
and tri-INTERCAL, but put together in a unique way.  It was designed to
be difficult to use, and so it is.  It is designed to be
incomprehensible, and so it is.

So far, no Malbolge programs have been written.  Thus, we cannot give an
example.

"Malbolge" is the name of Dante's Eighth Circle of Hell, in which
practitioners of deception (seducers, flatterers, simonists, thieves,
hypocrites, and so on) spend eternity.


Environment
^^^^^^^^^^^

In many languages, the environment is easy to understand.  In Malbolge,
it is best to understand the runtime environment before you ever see a
command.

The environment is, roughly, that of a primitive trinary CPU.  Both code
and data share the same space (the machine's memory segment), and there
are three registers.  Machine words are ten trits (trinary digits) wide,
giving a maximum possible value of 59048 (all numbers are unsigned).
Memory space is exactly 59049 words long.

The three registers are A, C, and D.  A is the accumulator, used for
data manipulation.  A is implicitly set to the value written by all
write operations on memory.  (Standard I/O, a distinctly non-chip-level
feature, is done directly with the A register.)

C is the code pointer.  It is automatically incremented after each
instruction, and points the instruction being executed.

D is the data pointer.  It, too, is automatically incremented after each
instruction, but the location it points to is used for the data
manipulation commands.

All registers begin with the value 0.

When the interpreter loads the program, it ignores all whitespace.  If
it encounters anything that is not one of an instruction and is not
whitespace, it will give an error, otherwise it loads the file, one non-
whitespace character per cell, into memory.  Cells which are not
initialized are set by performing op on the previous two cells
repetitively.


Commands
^^^^^^^^

When the interpreter tries to execute a program, it first checks to
see if the current instruction is a graphical ASCII character (33
through 126).  If it is, it subtracts 33 from it, adds C to it, mods it
by 94, then uses the result as an index into the following table of 94
characters:

            +b(29e*j1VMEKLyC})8&m#~W>qxdRp0wkrUo[D7,XTcA"lI
            .v%{gJh4G\-=O@5`_3i<?Z';FNQuY]szf$!BS/|t:Pn6^Ha

It then checks it against the characters listed below, and performs an
appropriate action.

If the result is not one of the characters listed below, it is treated
as a nop.  If the original character is not graphic ASCII, the program
is immediately ended.

When the interpreter parses the input file, it checks each non-
whitespace character with the process above.  If any result is not one
of the eight characters below, the file will be rejected.

After the instruction is executed, 33 is subtracted from the instruction
at C, and the result is used as an index in the table below.  The new
character is then placed at C, and then C is incremented.

            5z]&gqtyfr$(we4{WP)H-Zn,[%\3dL+Q;>U!pJS72FhOA1C
            B6v^=I_0/8|jsb9m<.TVac`uY*MK'X~xDl}REokN:#?G"i@

j
  sets the data pointer to the value in the cell pointed to by the
  current data pointer.

i
  sets the code pointer to the value in the cell pointed to be the
  current data pointer.

*
  rotates the trinary value of the cell pointed to by D to the right 1.
  The least significant trit becomes the most significant trit, and all
  others move one position to the left.

p
  performs a tritwise "op" on the value pointed to by D with the
  contents of A.  The op (don't look for pattern, it's not there) is:

            | A trit:
    ________|_0__1__2_
          0 | 1  0  0
      *D  1 | 1  0  2
     trit 2 | 2  2  1



Di-trits:
    00 01 02 10 11 12 20 21 22

00  04 03 03 01 00 00 01 00 00
01  04 03 05 01 00 02 01 00 02
02  05 05 04 02 02 01 02 02 01
10  04 03 03 01 00 00 07 06 06
11  04 03 05 01 00 02 07 06 08
12  05 05 04 02 02 01 08 08 07
20  07 06 06 07 06 06 04 03 03
21  07 06 08 07 06 08 04 03 05
22  08 08 07 08 08 07 05 05 04

<
  reads an ASCII value from the stdin and converts it to Trinary, then
  stores it in A.  10 (line feed) is considered 'newline', and
  2222222222t (59048 dec.) is EOF.

/
  converts the value in A to ASCII and writes it to stdout.  Writing
  10 is a newline.

v
  indicates a full stop for the machine.

o
  does nothing, except increment C and D, as all other instructions do.


Turing-Completeness
^^^^^^^^^^^^^^^^^^^

Though I have not proven it, I _think_ Malbolge to be Turing-complete.
To be Turing-complete, there must be some data construct which can be
used to do any mathematical calculation.  I believe that using *p in
various clever ways on the tritwords can fulfill this requirement.

Turing-completeness also requires three code constructs: sequential
execution (which Malbolge obviously has), repetition (provided by the
i and, indirectly, j instructions), and conditional-execution (provided,
I believe, by self-modifying code and altering i destinations).

I do have my doubts, particularly about data constructs, but I *think*
this works...


Appendix: Trinary Conversion Table
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Trinary to ASCII to decimal to hex table, provided, strangely enough,
for the convenience of Malbolge programmers.

00000 NUL 000 00    01012   032 20    02101 @ 064 40    10120 ` 096 60
00001 SOH 001 01    01020 ! 033 21    02102 A 065 41    10121 a 097 61
00002 STX 002 02    01021 " 034 22    02110 B 066 42    10122 b 098 62
00010 ETX 003 03    01022 # 035 23    02111 C 067 43    10200 c 099 63
00011 EOT 004 04    01100 $ 036 24    02112 D 068 44    10201 d 100 64
00012 ENQ 005 05    01101 % 037 25    02120 E 069 45    10202 e 101 65
00020 ACK 006 06    01102 & 038 26    02121 F 070 46    10210 f 102 66
00021 BEL 007 07    01110 ' 039 27    02122 G 071 47    10211 g 103 67
00022 BS  008 08    01111 ( 040 28    02200 H 072 48    10212 h 104 68
00100 HT  009 09    01112 ) 041 29    02201 I 073 49    10220 i 105 69
00101 LF  010 0a    01120 * 042 2a    02202 J 074 4a    10221 j 106 6a
00102 VT  011 0b    01121 + 043 2b    02210 K 075 4b    10222 k 107 6b
00110 FF  012 0c    01122 , 044 2c    02211 L 076 4c    11000 l 108 6c
00111 CR  013 0d    01200 - 045 2d    02212 M 077 4d    11001 m 109 6d
00112 SO  014 0e    01201 . 046 2e    02220 N 078 4e    11002 n 110 6e
00120 SI  015 0f    01202 / 047 2f    02221 O 079 4f    11010 o 111 6f
00121 DLE 016 10    01210 0 048 30    02222 P 080 50    11011 p 112 70
00122 DC1 017 11    01211 1 049 31    10000 Q 081 51    11012 q 113 71
00200 DC2 018 12    01212 2 050 32    10001 R 082 52    11020 r 114 72
00201 DC3 019 13    01220 3 051 33    10002 S 083 53    11021 s 115 73
00202 DC4 020 14    01221 4 052 34    10010 T 084 54    11022 t 116 74
00210 NAK 021 15    01222 5 053 35    10011 U 085 55    11100 u 117 75
00211 SYN 022 16    02000 6 054 36    10012 V 086 56    11101 v 118 76
00212 ETB 023 17    02001 7 055 37    10020 W 087 57    11102 w 119 77
00220 CAN 024 18    02002 8 056 38    10021 X 088 58    11110 x 120 78
00221 EM  025 19    02010 9 057 39    10022 Y 089 59    11111 y 121 79
00222 SUB 026 1a    02011 : 058 3a    10100 Z 090 5a    11112 z 122 7a
01000 ESC 027 1b    02012 ; 059 3b    10101 [ 091 5b    11120 { 123 7b
01001 FS  028 1c    02020 < 060 3c    10102 \ 092 5c    11121 | 124 7c
01002 GS  029 1d    02021 = 061 3d    10110 ] 093 5d    11122 } 125 7d
01010 RS  030 1e    02022 > 062 3e    10111 ^ 094 5e    11200 ~ 126 7e
01011 US  031 1f    02100 ? 063 3f    10112 _ 095 5f

11202 128 80    12221 160 a0    21010 192 c0    22022 224 e0
11210 129 81    12222 161 a1    21011 193 c1    22100 225 e1
11211 130 82    20000 162 a2    21012 194 c2    22101 226 e2
11212 131 83    20001 163 a3    21020 195 c3    22102 227 e3
11220 132 84    20002 164 a4    21021 196 c4    22110 228 e4
11221 133 85    20010 165 a5    21022 197 c5    22111 229 e5
11222 134 86    20011 166 a6    21100 198 c6    22112 230 e6
12000 135 87    20012 167 a7    21101 199 c7    22120 231 e7
12001 136 88    20020 168 a8    21102 200 c8    22121 232 e8
12002 137 89    20021 169 a9    21110 201 c9    22122 233 e9
12010 138 8a    20022 170 aa    21111 202 ca    22200 234 ea
12011 139 8b    20100 171 ab    21112 203 cb    22201 235 eb
12012 140 8c    20101 172 ac    21120 204 cc    22202 236 ec
12020 141 8d    20102 173 ad    21121 205 cd    22210 237 ed
12021 142 8e    20110 174 ae    21122 206 ce    22211 238 ee
12022 143 8f    20111 175 af    21200 207 cf    22212 239 ef
12100 144 90    20112 176 b0    21201 208 d0    22220 240 f0
12101 145 91    20120 177 b1    21202 209 d1    22221 241 f1
12102 146 92    20121 178 b2    21210 210 d2    22222 242 f2
12110 147 93    20122 179 b3    21211 211 d3
12111 148 94    20200 180 b4    21212 212 d4
12112 149 95    20201 181 b5    21220 213 d5
12120 150 96    20202 182 b6    21221 214 d6
12121 151 97    20210 183 b7    21222 215 d7
12122 152 98    20211 184 b8    22000 216 d8
12200 153 99    20212 185 b9    22001 217 d9
12201 154 9a    20220 186 ba    22002 218 da
12202 155 9b    20221 187 bb    22010 219 db
12210 156 9c    20222 188 bc    22011 220 dc
12211 157 9d    21000 189 bd    22012 221 dd
12212 158 9e    21001 190 be    22020 222 de
12220 159 9f    21002 191 bf    22021 223 df

Notes

Note that the original specification has one quirk: after encountering an illegal instruction, the interpreter hangs. You may choose which behaviour do you want to implement (hang or exit).

I/O rules

The program or function has to take input in any reasonable way (for the program), and somehow supply the input and output features to the malbolge program (either by return value / parameter, tty or a file).

Sandbox stuff

note: I'm a bit unsure about the scoring criterion: would popularity-contest be good? I'm mostly looking for creative answers

Answer 21

Write two programs (likely functions since IO for float convert to/from stream, losing info as mentioned later), one given \$n\geq 2\$ real points on a 2D plane, returning \$2n-3\$ real numbers; another given the \$2n-3\$ real numbers, return the same shape and size given to first program. Order of points matters. Returning a mirrored shape is fine.

You must use an in-language float and assume it is infinitely precise, but converting to types like string or trying to handle the bits in RAM truncate the precision. There's no requirements on how you map, so you can even just pack some real numbers into one if your language happens to have way to do that.

code-golf

Answer 22

What day is it today? atomic-code-golf

Given a date y4y3y2y1-m2m1-d2d1, output the day in the week w. 0 as Sunday, 1 as Monday, and so on. You can assume the date is valid, and we use the current date rule and leap rule.

Each submission should be written in this specific programming language:

• A program consists of a mapping from string of digits to digits, and a sequence of instructions.
• Each instruction has the format: var=[var|dgt],[var|dgt],...,[var|dgt], which assigns the value of looking up the string constructed by concatenating the values of the right hand side elements ([var|dgt],[var|dgt],...,[var|dgt]) together in the table and put it into the var on the left.

A program is valid if:

• None of the lookup step fails for all valid input date.
• Given any valid date in the format mentioned above (initially assigned to the 8 variables y4 y3 y2 y1 m2 m1 d2 d1), after the program is run, the correct result is assigned to the variable w.

You can create as many variables as you like(though bounded by amount of instructions), each variable only containing a digit.

Solution win if there's no strictly better solution, aka. no solution that take less or same amount of items in mapping table, less or same amount of instrucions, and at least one of amounts of items and instructions is less.

For example, this is a solution that wins:

3652425 items 1 instruction

003000101 -> 6
003000102 -> 0
003000103 -> 1
...
993991231 -> 5
-------------
w=y4,y3,3,y2,y1,m2,m1,d2,d1

Here, the 3 on 3rd position can be used without any extra cost. This can be used to create multiple mappings, and sometimes save elements when there are more mapping instructions.

A checker is provided here.

Answer 23

Natural Language Identification Using Only Regular Expressions

code-golf sandbox winning-criteria discussion

For example:

const regex = /English(?=\w+ Hello World)|Spanish(?= Hola Mundo)/;

console.log('EnglishSpanish Hello World'.match(regex)); // English
console.log('EnglishSpanish Hola Mundo'.match(regex)); // Spanish

These wordlists are to be used, and words are to be rewritten entirely using the ASCII characters A-Z and a-z. Languages which use characters that cannot be easily transcribed into ASCII without special knowledge or firsthand experience in that language, are excluded.

For instance, the Albanian word të is easily transcribed without special knowledge as te, so Albanian is allowed.

But the Arabic word من cannot be, so Arabic is excluded.

The regular expression must match the language exactly, so appending a list of all languages you are testing before each word is allowed. But however you organize this list, it must be the same for every word you test. See the example above for clarification.

Sandbox Questions

Ideally, brevity of regex, accuracy of language identification, and number of languages taken into account by the regex should all be considered when determining the winner. But I have not decided on that yet, and am very open to suggestions.

In fact this is my first sandbox post and I hope someone can help me format this properly with good rules so that it makes for an interesting and fun challenge. I got this idea from some other contest somewhere where the goal was to identify languages with at least 60% accuracy. But I can't find it anymore.

Answer 24

Rage Against the Dying of the Light

code-golfkolmogorov-complexity

Introduction

"Do not go gentle into that good night" is the title of a poem by 20th century English poet Dylan Thomas. If you've heard it before it was probably because you watched Interstellar, where it was quoted multiple times.

Challenge

Your program (or function), if it chooses to not go gently, should take no input and print the following text, with an optional trailing newline:

Do not go gentle into that good night,
Old age should burn and rave at close of day;
Rage, rage against the dying of the light.

Though wise men at their end know dark is right,
Because their words had forked no lightning they
Do not go gentle into that good night.

Good men, the last wave by, crying how bright
Their frail deeds might have danced in a green bay,
Rage, rage against the dying of the light.

Wild men who caught and sang the sun in flight,
And learn, too late, they grieved it on its way,
Do not go gentle into that good night.

Grave men, near death, who see with blinding sight
Blind eyes could blaze like meteors and be gay,
Rage, rage against the dying of the light.

And you, my father, there on the sad height,
Curse, bless, me now with your fierce tears, I pray.
Do not go gentle into that good night.
Rage, rage against the dying of the light.

This is code-colf, so smallest code in bytes wins.

Sanbox

• Is this too bland/simple of a challenge? There's a lot of potential for compressing the poem, but it's not really complex.

Answer 25

Anti-codegolf, unique characters

Objective

Write a program/method whose source code's characters are unique. You shall put as many characters as you can.

Input

There is no input.

Valid characters

All characters are identified by their Unicode code point. The following characters are invalid, and shall not appear in the source code nor the output:

• C0 and C1 control characters (U+0000 – U+001F and U+0080 – U+009F) except Character Tabulation (U+0009), Line Feed (U+000A), Line Tabulation (U+000B), Form Feed (U+000C), Carriage Return (U+000D), and Next Line (U+0085)

  • Outputting these characters are banned, even if they have special effect on an output stream.

• Low and High surrogates (U+D800 – U+DFFF)

• Noncharacters (U+FDD0 – U+FDEF, and U+xxFFFE and U+xxFFFF for xx = 00 – 10)

• Code points that are outside of U+0000 – U+10FFFF

A character is valid otherwise. In particular, whitespaces, combining characters, and private uses, and even reserved characters are valid.

Restrictions and output

Your program shall halt.

The output shall be a string. This includes string returned by a function, or string printed to stdout, stderr, a file, or a dialog box.

The set of the characters in the source code shall be a subset of the set of the characters in the output. Note that the output doesn't need to consist of unique characters.

The output may be arbitrarily many strings, for which their concateration will be considered for the restriction above.

Scoring

This is an anti-codegolf. The submission with the longest source code wins.

Answer 26

Gray codegolf

The gray code is a binary numeral system such that two successive values differ in only one bit.

Decimal Binary  Gray
0       0000    0000
1       0001    0001
2       0010    0011
3       0011    0010
4       0100    0110
5       0101    0111
6       0110    0101
7       0111    0100
8       1000    1100
9       1001    1101
10      1010    1111
11      1011    1110
12      1100    1010
13      1101    1011
14      1110    1001
15      1111    1000

Challange

Print the first k Gray code numbers, starting from 0. The shortest code wins!

You may choose the output format as long as it's human-readable.

Similar questions

• Give me the Gray Code list of bit width n This question is not a code-golf and has different output requirements
• write a code the find n-th number of Gray Code list This question is a code-golf(at some point) but only asks to output one number

Answer 27

B-a-NaN-a code-golfkolmogorov-complexityrestricted-source

Somewhat famously, 'B' + 'a' + + 'a' + 'a' returns BaNaNa in Javascript. You goal is to output precisely BaNaNa. However, to keep it more in the style of the original Javascript, you may not use:

• The bytes 78 or 110
• Whatever n or N are encoded as if your language uses a special encoding, or
• Any string literal containing the characters n or N

in your source code.

As a special note, I'd like your feedback as to if restricting numeric literals equal to 78 and 110 would be any good.

Additionally, this is my first question, and I'm aware that 'Do X without Y' is officially not super popular these days, but I frankly quite enjoy them, so I have no idea if this will be well-received or not. I'm hoping that the reference to the JS quirk is enough to make it interesting.

Answer 28

Find the nth positive integer m for which \$\tan(m) > m\$ code-golf math

Task

Write a program/function that when given an integer \$n\$ as input outputs the \$n\$th positive integer \$m\$ for which \$\tan(m) \gt m\$.

Note: \$m\$ is in radians

Scoring

This is code-golf so shortest bytes wins.

Sample Testcases

# n -> m
1   -> 1
2   -> 260515
3   -> 37362253
5   -> 534483448
9   -> 214112296674652
10  -> 642336890023956
16  -> 4285797387061825747646013

Find more at A249836

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Inspired by What is the biggest tangent of a prime?

Answer 29

Is it a Pythagorean triple? code-golf decision-problem geometry math number-theory

Given three numbers, determine whether they form a primitive Pythagorean triple. Here is the definition:

• all three numbers are positive integers
• they represent the side lengths of a right-angled triangle, that is, \$a^2 + b^2 = c^2\$ for any ordering of \$a\$, \$b\$, and \$c\$
• no other primitive Pythagorean triple exists with the same ratio of side lengths, that is, they are coprime. For example, \$[6, 8, 10]\$ is not a primitive Pythagorean triple, even though it satisfies the above conditions, because the simper \$[3, 4, 5]\$ exists.

Rules

• Unless your language doesn't support them, you must accept floating-point numbers (even though Pythagorean Triples use, by definition, integers)
  • meta: Is this necessary? Is it too restrictive?
• You may be given negative numbers, \$0\$, or numbers that cannot form any triangle (right-angled or not, i.e. \$a + b \le c\$), in which cases you must return false.
  • meta: Is this necessary? Does it make it too difficult?
• You can return any two distinct individual values, or any typical truthy/falsey values for your language.
• Standard I/O and loophole rules apply.
• This is code-golf, so shortest function or full program in bytes wins.

Test Cases

[0, 3, 3] => false
[3, 4, 5] => true
[5, 3, 4] => true
[3, 4, 6] => false
[3, 4, 10] => false
[6, 8, 10] => false
[3.0, 4.0, 5.0] => true
[3.1, 4.0, 5.0] => false
[-3, -4, -5] => false
[3, 4, -5] => false
[4.5, 6, 7.5] => false
[91, 60, 109] => true
[264, 265, 23] => true
[81, 210, 184] => false
[140, 221, 83] => false

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Meta

• Are the first two rules necessary, or do they restrict it too much?
• Is it clear enough? Are there any additional rules I need to add? Are more test cases needed?
• Does this suit the geometry and number-theory tags? It's kind of tangential to both areas.
• Is this decision-problem too similar to the existing sequence questions that want you to generate triples?

Answer 30

Am I A Perfect Two Integer?

A “perfect two integer” is an integer that works as x in the following equations:

Let i = integer, j = integer, x = perfect two integer:
2^i = x
j^2 = x

Example “perfect two integers”: 4, 16, 64, 256, 1024 (see a pattern here?)

Your answer should take a number from stdin or an argument. This should be relatively easy, but this is code-golf, so the shortest answer wins. (Note: there are ways to simplify these equations that aren’t listed here).

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Sandbox Questions:

1. Is this a duplicate?
2. Is this too easy?
3. Any other thoughts?