Sandbox for Proposed Challenges

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Answer 1

Comparing Strings

code-golf string

You will be given two non-empty strings containing printable ASCII. If their contents are exactly the same, output their contents. If their contents are different, output a third string. This third string cannot be a substring of either string, and neither string can be a substring of it.

Test Cases

Test cases are quoted to show they are strings. Outputs marked with * indicate they are one of infinitely many possible outputs.

input, input -> output

"test", "test" -> "test"
"do", "don't" -> "dnut"*
"ye s", "yes" -> "false"*
"yes", "yes" -> "yes"
"maybe", "mayue" -> "false"*
"false", "false" -> "false"
"false", "true" -> "fatr"*

Rules

• The inputs will be composed of only printable ASCII - that is, space to tilde. Your output should also be composed of only printable ASCII, but a trailing newline is allowed.
• Your algorithm may not make any assumption about the length of the inputs, except that they will not be empty.
• The output must be valid with probability 1; that is, you may generate random strings until one is valid, but you can't just output a random string and hope it's valid. Source
• Trailing newlines in output allowed (otherwise there will be no newlines - newlines are not in printable ASCII).

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

Answer 2

Can you generate this random sequence for me?

Inspired by this question on Retrocomputing

I want to create a random generator that always returns a desired word. I desperately need this so I can hide some easter eggs. For science easter!

Input

A word, either in string format or an array or vector of characters. You can assume all lowercase and only the regular characters a-z.

Task

Write a full program or function that finds a seed such that when taking a random sample of letters, the desired word is output. The function then should return or save another full program or function that does the generating of this desired word.

Rules

• The returned function of program should use random sampling to create the output, so it is not allowed to hardcode (obligatory XKCD)
• The output can be written to file in the case of a full program or returned.
• Hiding an easter eggs is easiest when there is little code, so the shortest code wins.
• If there is no seed that generates the required output, your program is allowed to run forever.
• Standard codegolf rules and loopholes apply.

Example implementation:

> f <- function(string){
+     seed <- 1
+     set.seed(seed)
+     repeat{
+         seed <- seed + 1
+         set.seed(seed)
+         if(all(sample(letters, length(string), replace = TRUE) == string)){
+             break
+         }
+     }
+     generator <- function(){
+         set.seed(seed)
+         sample(letters, length(string), replace = TRUE)
+     }
+     return(generator)
+ }
> f("a")
function(){
        set.seed(seed)
        sample(letters, length(string), replace = TRUE)
    }
<bytecode: 0x000000001c83f2d8>
<environment: 0x000000001f906c20>
> g=f("a")
> g()
[1] "a"
> g()
[1] "a"
> g()
[1] "a"

Answer 3

Make it night! ^{_{popularity-contest image-processing}}

You just went on vacation to see some scenery in the beautiful night. Unfortunately, your alarm clock malfunctions and when you wake up, it's daytime.

Your mother would like to see some photos, but you can only take pictures in the day. You would like to be able to convert these daytime pictures to pictures in the nighttime.

Challenge

Given an image taken in the daytime, process it and turn it into night time as best as you can.

Sometimes it might be hard to do, like images that have a sun, but you can write your algorithm to remove the sun or do something else.

Example

(I did this by hand, so it might not be that good)

Voting

Please vote accordingly to how well the algorithms perform.

• Is the sky dark like a night sky?
• Does the picture look photoshopped/edited?
• Are there vivid colors that shouldn't appear in the night?
• If you were showed both images, would you believe that there was no processing?

(If you have a suggestion, please comment.)

Test Cases

Winning

Since this is a popularity-contest, the answer with the highest score (upvotes minus downvotes) wins.

Answer 4

Intertwined Polyglot

polyglot code-golf

Write a program which when executed as language A, produces a different program in language B, which in turn produces the name of language A. And the other way round (B to A to B).

+-----------+   Lang. A    +-----------+   Lang. B
| Program 1 | -----------> | Program 2 | -----------> "<Lang. A>"
|           |              +-----------+
|   Your    |              +-----------+
|  Program  | -----------> | Program 3 | -----------> "<Lang. B>"
+-----------+   Lang. B    +-----------+   Lang. A

Rules

• The produced programs must be unique both from each other, and from the original program.
• Uniqueness is defined as at least one modified or moved printing character. Example: a bc => ab c would not be considered unique, whereas a bc=> a cb would.
• The output may contain leading and/or trailing whitespace and/or newlines, so long as the language name is intact.
• Your program(s) may not take any input.
• This is code-golf, so fewest bytes wins.

Answer 5

Multiplicity of a Curve

code-golfmathpolynomialsabstract-algebrageometry

Given an polynomial p in two variables x and y as well as a point (u,v), determine the multiplicity m of the curve C = { (x,y) | p(x,y) = 0} at the point (u,v).

Details

• The degree of a monomial a * x^i * y^j in two variables is d = i+j.
• A polynomial is homogeneous if all its monomials have the same degree d.
• Any polynomial p (where d is the degree of p, i.e. the maximum of the degree of all its monomials) can uniquely be decomposed into a sum of polynomials p = p0 + p1 + ... + pd where each pk is homogeneous of degree k OR possibly zero.

• The multiplicity of a curve C given by the polynomial p at (u,v) can be determined using the following computation:

  • First decompose the polynomial p(x-u,y-v) (this is p with x,y replaced with x-u,y-v) into a sum of homogeneous polynomials as described above:

    p(x-u,y-v) = q0 + q1 + ... + qd
    

  • Then determine the minimal k such that qk is nonzero. Then the multiplicity is defined as m := k.

Example

Let us consider the polynomial p(x,y) = -x^2 - 4x + y^2 - 2y -3 and the point (u,v) = (-2,1).

p(x-u,y-v) = y^2 - x^3

So the decomposition is

p(x-u,y-v) = [0] + [0] + [y^2] + [-x^3]

Here the brackets are just used to highlight the homogeneous polynomials of each degree.

We see that y^2 is the nonzero polynomial of least degree, so m = 2

TODO

• add more testcases

Answer 6

Code the beach on the beach (heavily WIP)

The Gods of the Sea have seen your coding ability and asked you to rewrite their beach-generating program.

Code the beach

This program will take no input and, in this order:

• Print sand (.)
• Print ocean waves (~)
• Print crabs (>.<)
• Print seagulls (-v-)

This program will be run by the Gods of the Sea. They will run it once a day and will want a different beach every time they run it, so the beach items should be generated (pseudo)randomly.

To avoid this beach becoming overloaded, there should be:

• Between five and eight crabs
• Between three and seven seagulls
• Between eighty and one hundred grains of sand
• Eighty ocean waves

Your program should create the beach just as the Gods' existing program does. It will first draw the sand at the bottom of the screen, in the last three lines. Example sand:

. .. .. . . ... . ... ..  . ..  .... .. . ... . .. . .. . . .. . .. . . .... ...
  .. . .. .. .. .. ... .   ..  .. ... ...  .   .   ....... .... ...... ... .
. . . .. .. ...... ... .. ......... .  .... .. . . . . ... .. .. . . . ...

Then the waves will be printed, starting from the leftmost character in the fourth-to-last line. The point where the waves meet the sand should vary by at most one character, and waves should never go off the screen. All water that is not curling in a wave will cover the sand, so there can be no sand under the water. Example waves:

TODO: Add example waves

Crabs should be spawned in the last four lines and cannot be spawned on waves, because if they were, they would be quickly sucked under and disappear.

Seagulls may be spawned anywhere, and should be evenly distributed to the best of your pRNG's ability.

On the beach

The Gods were born in ancient times, so they're still using VGA; their terminal has 80x25 characters for output, as does their text editor - which is so old it does not support scrolling. Your program will have to fit in this text editor, so it will need to be small.

The Gods do not yet have the internet, so you'll have to write your program on the beach in a location they can see it. Unfortunately, the only convenient place at the moment is a very small sandbar on the Oregon coast. Waves occasionally reach this spot. To make sure you have enough time write the entire program before it's washed away, it will need to be as small as possible.

Furthermore, since the Gods are so far away, some characters written in the sand are indistinguishable. Gods are good at guessing, so if they see a character that looks like another they'll get it right, but another character that looks similar to the character they guessed will be assumed to be said previous character. So if a l is present in the source before an I, the Gods will see two ls.

Here are the lookalikes:

• o and O
• l and I and |
• : and ;
• " and '

The Gods don't have the technology to easily use Unicode characters, so you'll have to give them a lot of help. Each non-ASCII character you use will cost 5 bytes to describe it to them.

Answer 7

Numbers to Algorithms

Another horrible part of Cubically is attempting to print numbers when the notepad is occupied. Since you can't add up existing faces, the integer (or ASCII value) you have to print needs to be on one single face.

The maximum value you can store on one Cubically face is 45. This isn't great, but it's better than nothing. Your challenge is to write a program that automates the process of getting the values 0-45 onto the top face.

Your program will take an input number n and produce a Cubically code snippet as output. This Cubically snippet should achieve the task of getting all integers on the top face to sum up to n. If you don't yet know how Cubically works, go check out the repo. Here's a run-down of all you need to know.

Cubically is my esolang based on a Rubik's Cube. Its 3x3x3 memory cube is initialized like this (without the comments on the right):

   000
   000          top face
   000
111222333444    left, front, right, and back faces, respectively
111222333444
111222333444
   555
   555          down face
   555

It uses quarter turn notation, so RRLL turns the cube to look like this:

   505
   505
   505
111424333242
111424333242
111424333242
   050
   050
   050

Now the sum of the top face is 30. So if n is 30, RRLL would be a valid output.

In addition to quarter turn notation, you can send a subscript number to face turns to mean "turn the xth layer inwards from the [face] face, where x is the subscript number". So R1 would turn the cube to look like this:

Answer 8

Arbitrary base conversion

code-golf base-conversion

Given an integer n of any sign, output a list of digits of its representation in a given base b not in -1, 0, 1. If b is positive, n will be non-negative.

Rules:

• You may not use arbitrary base conversion built-ins like Jelly's b or 05AB1E's в.
• You may assume the input is valid, as above.
• All digits must be greater than or equal to 0 and strictly less than b.
• For zero you must return [].

Test cases

256, 10 -> [2, 5, 6]
256, -10 -> [3, 5, 6]
1000, 25 -> [1, 15, 0]
1000, -30 -> [2, 27, 10]
0, 300 -> [0]
1000, 1000 -> [1, 0]
18446744073709551615, 4 -> [3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3]
18446744073709551615, -5 -> [3, 3, 2, 1, 3, 3, 1, 2, 1, 2, 2, 3, 0, 1, 1, 4, 0, 2, 0, 4, 3, 4, 2, 3, 3, 1, 4, 4]

Sandbox

Is this a dupe?

Answer 9

Bomberman

Given an input Bomberman board b, use the following characters to define the different bomberman tiles:

• X denotes the outer boundary of the board.
  • X is always in each of the four corners of the board.
  • X may only be on the boundaries of the board.
• - denotes an empty space.
  • When a bomb blows up over an empty space, it replaces it with *; and may continue.
• o denotes a blocker that is breakable.
  • When a bomb blows up over a breakable blocker, it replaces it with *; and stops.
• O denotes an impenetrable blocker.
  • When a bomb reaches an impenetrable blocker, it stops prior to it.
• 0-9 describes a bomb of n power.
  • When a bomb explodes it explodes in a plus pattern.
  • A bomb of 0 strength would be: *.
  • A bomb of 1 strength would be: * \n***\n *
  • And so on... 1-indexing is not okay because that would make the 9 bomb a 10 bomb.

---

Worked Example

An example board would be (without bombs):

XXXXXXXXXXXX
X----------X
X-oo---O---X
X--------O-X
X--OoO-----X
X----------X
X--O-------X
X-------O--X
-----o------
X---------OX
X--O---o---X
XXXXXXXXXXXX

If we were to add some randomized bombs to this board we would see:

XXXXXXXXXXXX
X----------X
X-oo-1-O---X
X--------O-X
X--OoO--0--X
X---1------X
X--O-3-----X
X-------O--X
--4--o------
X---------OX
X--O-2-o---X
XXXXXXXXXXXX

This should, when input to your program, output the following explosion pattern:

XXXXXXXXXXXX
X----*-----X
X-oo***O---X # This didn't get blocked, it's just a small explosion.
X----*---O-X
X-*O*O--*--X # This destroyed a brittle block.
X-****-----X
X-*O*****--X # This got hard blocked.
X-*--*--O--X
*******---** # Notice how it wraps, because there's no boundary.
X-*--*----OX
X-*O****---X # This got hard-blocked.
XXXXXXXXXXXX

---

Example 1:

Input:

XX
XX

Output:

XX
XX

---

Example 2:

Input:

X-O--X
-o2-o-
-1--1-
-o-2o-
X--O-X

Output:

X-O--X
-****-
******
-****-
X--O-X

---

Example 3:

Input:

X     X
 OOOO
  1114


X     X

Output:

X    *X
 OOOO*
*******
  ****
     *
X    *X

---

Rules

• Boards must be rectangular or square.
• Boards must have blockers on the corners of the rectangle/square.
• code-golfawesomeretro-ascii

More examples, soon. Is this good? Sandbox? What should I change?

Answer 10

Is Effort Inversely Correlated with Upvotes?

Inspired by this chat message and the subsequent conversation

Introduction

PPCG is infamous (famous?) for it's short golfing language answers that are showered with upvotes. But, are these short answers full of hard-core golfing, or are they just a few builtins that work? Do these answers take effort, and deserve upvotes, or are upvotes and effort inversely correlated?

The Challenge

To get some variables out of the way, x=effort, and y=votes

Your challenge is, given a question ID, output A if the question has a strong positive correlation between effort and votes, B if it has a weak correlation between efforts and votes, or C if it has a strong negative correlation between effort and votes. A may be any value never given as B or C, B may be any value never given as A or C, and C may be any value never given as A or B (You doubt have to have consistent values across runs, but the set of values for A must not intersect with B or C, etc.).

Defining Effort

Effort is an awfully complex concept, but for this challenge we will grossly simplify it to the number of significant edits. significant edits, in this context, will be the number of edits, by the question author, that occurred more than 1 minute after the previous edit (initial posting, in this case, counts as an edit).

Defining Votes

Votes is upVotes - downVotes.

Defining Correlation

For the sake of simplicity, will we use the least-squares regression line as our correlation model. If R^2 (the determination coefficient) is less than .3 (e.g. < 30% of the variation is explained by the model), we will say that there is weak correlation. If R^2 is greater than or equal to .3, we will say that the correlation is strong. Negative vs. positive correlation must be determined from the sign of R (the correlation coefficient).

What Points?

The data points that should be included in your regression are points of the form (votes, effort) for each answer in the given question.

Test Cases

//TODO

Specifics

• For the purposes of this challenge, you may access the api.stackexchange.com website. You may not shorten the URL with any out-of-language utilities (e.g. tinyurl, but you can still compress it if your language supports compression)
• You may not violate any standard loopholes
• You may take input and give output in any reasonable format
• You should exclude community wikis from your calculations

Meta

• Question is a work in progress
• Anyone have a good title
• How valid are my statistics?
• code-golf, stack-exchange-api

Answer 11

Word Problem Generator popularity-contest

Already exists here!

Word problems can be a great way to test comprehension of concepts, but they are pain to write. That's why you need to make a program that takes an equation (or set of equations), and makes a word problem out of them. For example, if the input is x+3=8, you can output, Mary has 3 more apples than Johnny. If Mary has 8 apples, how many does Johnny have?

The best answers for this challenge will be able to handle many different types of equations and randomly generate a variety of unique word problems. It might be o.k. if your program creates non-sensical word problems, as long as they describe the input equation/equation set and people like them.

Rules

• Submission must be no longer than 2000 bytes
• External files and URL's may be used to access word lists not specifically made for this challenge. You can also use libraries for parsing mathematical equations and sentence generation that were not specifically made for this challenge (WolframAlpha is acceptable). Inquire about other acceptable usage of external sources.
• Golfing is encouraged. Most popularity contests ask for readable code, but with a tight 2000 byte limit, I encourage golfing as much as possible (even using a golfing language), so that you'll have enough bytes remaining to create interesting word problems.

Examples

• atan(x) = 5/4 => "At what angle should Jan hit the soccer ball to hit a target 5 feet high and 4 feet away?"
• x+5 = y, 2(x-1) = y-1 => "Paul is 5 years older than Sally. Last year Paul was twice Sally's age. How old are Paul and Sally?"
• x = 6^2/4^2 => "How much more pizza is there in a 12 inch pizza than an 8 inch pizza?"

Submission

With your submission, you include the types of equations/equation sets it can handle (we'll assume that a,b,c,d,e,f,g refer to constants and t,u,v,w,x,y,z refer to variables).

As an example, let's say your program can only make 1 type of word problem: "How long will it take for a boat with speed a to catch up to a boat with speed b that is distance c ahead of the first boat?" In that case, you write that your program only handles equations of the form at = bt + c, so people will know to only test it with things like 5t = 3t + 2 or 4t = 2t + 1.

Furthermore, you should mention if your program can make multiple types of word problems for one type of equation/equation set. For example, an equation of the form a + bx = c could lead to word problems about the time it takes to get from one point to another, or the amount of a particular coin you need to reach a certain amount of money.

Likewise, mention other ways your program creates variety in generating word problems.

Finally, you can include some sample word problems your program has generated, and the equations they were for.

Minimum Requirements

The most basic acceptable solution should handle at least 1 equation/equation set with at least 1 variable, 1 constant, and 1 mathematical operation. Such a minimal program might only handle equations of the form x = a + 1. It might output word problems like, "If Jerry has a apples, and he picks 1 more, how many does he have now?" Obviously, you should not strive for the bare minimum.

---

All suggestions welcome!

Answer 12

Help Me Catch Up With xkcd! code-golfinternet

I definitely enjoy xkcd, and you, as a code golfer, most likely enjoy it as well. However, I often find that I won't check the website for a while and there will be a lot to read! So, I want to make a solution for that. In proper code golf fashion.

---

The Challenge

Your task is to write a program which, when run, will check for a new xkcd and, if there is a new comic (in other words, it is different from the one when the program last ran), output the text "There's a new xkcd out!". Use this method to check:

1. When the program is run, check if there is a file named .xkcd in the user's home directory. If not, create the file, which will contain the title of the current xkcd comic, then exit.
2. If the file .xkcd does exist in the user's home directory, the program will check if the title of the xkcd comic on the front page of xkcd.com is the same as the one in .xkcd. If it is, the program will exit and do nothing else. However, if the titles aren't the same, the program will output the specified text, change the contents of .xkcd to the new title, then exit.

If you have any other methods, tell me about them.

---

This is code-golf, so may the shortest code win and the best programmer prosper...

Answer 13

code-golf? code-challenge? answer-chaining string

JS, 44 bytes

Here's a list of languages & byte counts from PPCG:

Jelly, 27 bytes
Mathematica, 174 bytes
Scala, 91 bytes
05AB1E, 12 bytes
dc, 13 bytes
Python 2, 115 bytes
V, 25 bytes
Charcoal, 48 bytes
Jelly, 10 bytes
Haskell, 25 bytes
MATL, 14 bytes
x86-16, 43 bytes
Emoji, 50 bytes
Pyth, 9 bytes
C, 38 bytes
JavaScript, 69 bytes
R, 73 bytes
Node.js, 70 bytes
Ly, 7 bytes
Japt, 7 bytes
Java, 2777 bytes
Husk, 18 bytes
Beatnik, 148 bytes
APL, 10 bytes
Powershell, 127 bytes
Python 3, 111 bytes
Ruby, 38 bytes
Cubically, 1231 bytes
C++, 292 bytes
Common, 98 bytes
Swift 4, 63 bytes
Axiom, 91 bytes
Groovy, 7 bytes
Bitmap, 160 bytes
Batch, 86 bytes
Perl 5, 34 bytes
Pyke, 7 bytes
Java, 182 bytes
PHP, 1 bytes
C#, 163 bytes
Processing, 85 bytes
Tcl, 66 bytes
PowerShell, 11 bytes
LOGO, 33 bytes
axo, 22 bytes
Excel, 37 bytes
TXR Lisp, 76 bytes
Alice, 17 bytes
Moorhens, 716 bytes
PHP, 2943 bytes
Python, 79 bytes
QBIC, 25 bytes
D, 65 bytes
Emojicode, 50 bytes
REXX, 46 bytes
BBC, 70 bytes
Retina, 24 bytes
Bash, 74 bytes
Cubix, 28 bytes
cQuents, 7 bytes
J, 90 bytes
AHK, 110 bytes
Mathics, 46 bytes
RProgN 2, 8 bytes
SOGL, 36 bytes
Röda, 36 bytes
><>, 238 bytes
QuadR, 32 bytes
C#, 289 bytes
Bash, 385 bytes
JS, 2823 bytes
C, 14 bytes
HTML, 132 bytes
Ruby, 40 bytes
JS, 130 bytes
Gaia, 17 bytes
TI-BASIC, 17 bytes
Befunge, 10 bytes
Ruby 2.4, 53 bytes
Pari/GP, 21 bytes
Actually, 10 bytes
APL, 4 bytes
TXR, 74 bytes
Sage, 102 bytes
Grime, 28 bytes
Ruby, 101 bytes
C++17, 71 bytes
Perl, 41 bytes
CPython, 25984 bytes
SmileBASIC, 43 bytes
WendyScript, 50 bytes
Python, 2969 bytes
Clojure, 156 bytes
Lost, 57 bytes
C++, 19 bytes
Brachylog, 4 bytes
Octave, 25 bytes
C#, 123 bytes
Magneson, 102 bytes
Brain-Flak, 36 bytes

This list will change before this challenge is posted.

Your challenge

Look at the program before you. It will print something like JS, 23 bytes. That means that you must use JS as your language.

Then pick a line from the list. Let's say you pick LOGO, 33 bytes. That means that you must print LOGO, 33 bytes in JS.

Because LOGO, 33 bytes is the 44th line, your byte count modulo the number of languages in the list (there are 100) must equal 44.

The three restrictions:

• You must use JS
• You must print LOGO, 33 bytes
• Your byte count modulo 100 must be 44

So a valid submission might be:

x=>"LOGO, 33 bytes"//just wasting some bytes

Then, after your submission, you add the list from the last answer to your answer. Then, you remove Logo, 33 bytes from the list: (in your answer, not the question)

That's the language you used, and the byte count you used. Add it to the bottom. Dupes are OK.

Your answer will look like this:

JS, 44 bytes

x=>"LOGO, 33 bytes"//just wasting some bytes

Here's the new list:

(Insert the list here, and remove `Logo, 33 bytes`)

The next submission must use Logo.

Note that the list will continually get smaller, making the challenge harder.

---

Meta

• Winning criterion? Last answer? Second-to-last? code-golf
• Unclear?
• Dupe?

Answer 14

code-golf internet string

Where in the world am I?

Original Challenge

This challenge has a single aim, given no input, print out the user's current location, with a minimum of the following info:

• City
• Country

So any of the following are allowed:

• "London, England"
• "Eifel Tower, Paris, France"
• ["London", "England"]
• {"country": "Scotland", "city": "Edinburgh"}

The following are not allowed:

• [51.5074, 0.1278]
• {"country": "Scotland", "city": "Edinburgh", ISP: "EE"}

Do not show the user's IP or ISP name, or any extra output.

Standard code golf rules apply

Good luck, and have fun!

Reason for limits

• No ISP or IP
  • Stops just using ipinfo.io
• No long and lat
  • This has already been a challenge

Thanks

programmer5000 - Suggesting to post here after original was deleted

caird coinheringaahing - Lon and Lat rules

Answer 15

Paint with Pride!

Task: Output a 6 banded version of the pride flag

Details:

The flag consists of 6 bands of colour, each band is rectangular, and all are the same size which is 9x1 units (WxH) . These bands are stacked one on top of each other in the order shown to form a flag that is 9x6 units in size.

The output scale can be chosen by the participant, but all components must be in those ratios, that is, an output must have an aspect ratio which is a multiple of 3:2.

The hexadecimal values and relative positions of the colours are as below:

Or from top to bottom RGB (255,0,0), (255,153,0), (255,255,0), (0,153,0), (0,0,255), (204,0,153)

A minimal version would look like this:

Acceptable output:

Output to screen or as a file in a commonly accepted image format is allowed, ascii art is however not.

Sandbox notes:

related, related

I chose this flag because I think the rainbow provides potential for an additional mathematical element

I'm not sure whether to include a minimum size limit, such as the one for drawing the french flag, as perhaps the small output size allows hardcoded answers to succeed (which I don't really want) - any advice?

Answer 16

The source of pi

_{Inspired by an International Obfuscated C Code Contest entry.}

Task

As you all know, pi is a constant that represents the ratio of a circle's circumference to its diameter.

Using the dimensions of your own source code, approximate pi to at least two decimal places.

That is, your source code should read itself to obtain both circumference and diameter, then output the ratio.

For example, if your code is:

 AB
CDEF
 GH

Your circumference is 14 and your diameter is 4.

For the purposes of this challenge, let diameter equal the larger of the height or width of your code.

Rules

• Take no input
• Hardcoded values for pi are not allowed
• Output pi to at least two decimal places (e.g., 3.14 and 3.1415 are both acceptable outputs)
• Answers can be either whole programs or functions

Notes

Answers with higher precision values are acceptable.

Standard code-golf rules apply.

---

Meta

Looking for suggestions of a better title.

Answer 17

"Square Root of Pi(e)"

ascii-art graphical-output

A pie (r=3) is drawn as such:

  @@
 @@@@
@@@@@@
 @@@@
  @@

Pretending that it's a perfect circle, the square root of such a pie would be sqrt(PI*32) = 3sqrt(PI) ~ 5.317. Now take a square out of the pie, whose area is closest to the square root of the pie. In this case it would be a square of area 4. Therefore, you can output:

  @@
 @@@@
@@  @@
 @  @
  @@

Yep, I took a square out of the pie, how do you like that?

---

r=7

      @@
     @@@@
    @@@@@@
   @@@@@@@@
  @@@@@@@@@@ 
 @@@@@@@@@@@@
@@@@@@@@@@@@@@
 @@@@@@@@@@@@
  @@@@@@@@@@
   @@@@@@@@
    @@@@@@
     @@@@
      @@ 

7*sqrt(PI) ~ 12.407. Closer to 3x3 than 4x4 square.

      @@
     @@@@
    @@@@@@
   @@@@@@@@
  @@@@@@@@@@ 
 @@@@@@@@@@@@
@@@@@@@@@@@@@@
 @@@@@@   @@@
  @@@@@   @@
   @@@@   @
    @@@@@@
     @@@@
      @@ 

Specifications:

1. Input will be only a "pie" with integer radius of at least two. As you can see, the longest row has 2r @s, and the smallest rows have 2 @s.
2. You can use a symbol other than "@".
3. You can take a square out of the inside or the edge.
4. Approximate PI to at least 3.14.

Bonus: Valid answers that are in a language with food-related name get a free upvote!

Answer 18

The Best Question

code-golf stack-exchange-api

This site gets a variety of questions: the good, the bad, the ugly. However, I've noticed some patterns that I think will help us find The Best Question (of a given week).

Procedure

You are given a date in a human-readable format of your choice as input. You need to find the best question from that week. The week starts on Sunday and ends on Saturday. Click on the link for a valid query to use if the input is Aug 31, 2017. Note that when using the API without a key you can use UNIX epoch time or YYYY-MM-DD to specify the dates (info here). Since this site gets only about 45 questions a week, you can assume that no more than 100 questions will be asked in a given week in order to avoid pagination.

Scoring

First of all, closed questions are disqualified. Next, here is the formula for Question Rating (QR)¹, given Question Score (S) and Number of Answers (A):

The thinking is that there are two kinds of questions that undeservedly get a very high question score: 1) the ones that are easy and get a lot of answers, and 2) the ones that are so difficult that they get few or no answers. I've determined that the best questions have a QuestionScore:Answer ratio of about 3:2.

Output

All you have to do is output the full URL of the question that got the best question score. If multiple tie, you can output them all or just one.

Example

Here's a list of 8 imaginary questions, with their question score followed by the number of answers they received, and their resulting QR:

1. +6, 23A -> -0.333
2. +10, 0A -> 7.78
3. +8, 4A -> 7.56
4. -2, 6A -> -4.44
5. +5, 3A [closed] -> DQ
6. +20 2A -> 16.22
7. +24, 40A -> 16
8. +15, 14A -> 13.67

So the winner is question 6. Output its URL.

Note

You don't need to handle the rare edge case when there are no valid questions in a given week.

_{¹Disclaimer: This scoring system is just a joke.}

---

Suggestions on formula and other stuff welcome.

Answer 19

Extend the Pattern

code-golfimage-processinggraphical-output Given a raster image with a lattice pattern, extend it to twice the size of the input image in both directions.

Details

The input image is a section of an infinite repeating pattern defined by two vectors u=(ux,uy),v=(vx,vy) with integer entries, that are linearly independent. This means that both vectors are nonzero and do not point in the same direction. The pattern is defined such that the pixel at a point p = (x,y) has the exact same colour as the pixel at

q := p + s*u + t*v 

for every integer s,t. This means if you know the colours of the pixels within the fundamental parallelogram Z = { s*u + t*v | s in [0,1),t in [0,1)} and corresponding vectors u,v you can extend the pattern to an arbitrary size. The goal of this challenge is finding the pattern and extend the image.

Specs

• You can take the input image in any non-compressed image format that allows for at least 3 colours, this includes e.g. matrices, 2d arrays or strings.
• The input method must match the output method. That means if you read a .png file as input, you must also write a .png file as output, or if you take the input via console, you must also print the output via console e.t.c.

Examples

(to be added...)

Answer 20

Golf a Brainfuck compresser.

The eso-lang Brainfuck only has 8 instructions that do something: +-><[],. so in theory you could represent them in 3 bits. You could store 8 instructions in 24 bits or 3 bytes.

BrnFck

This is compressed brainfuck an instruction will be represented by its bits.

1. + : 000
2. - : 001
3. > : 010
4. < : 011
5. [ : 100
6. ] : 101
7. , : 110
8. . : 111

This is a language counted in bits, 8 bits is 1 byte depending on the challenge you may round up or keep a decimal.

The goal

Write the shortest program that can compile any inputted brainfuck code to BrnFck code:

• You can choose how you output it, byte,bit/boolean arrays and output streams are all acceptable. Just printing ASCII-letters is too.
• You can do anything (including crash) if the input isn't valid code or contains a non-bf character.

And can compile the BrnFck code back to Brainfuck (or any other language (except BrnFck)). You may ask which way you want to compile or write 2 separate programs/functions and sum their scores.

If you post the code online (for example as an answer) this should automatically allow BrnFck as a language in all future challenges!

Scoring

If you use brainfuck you can divide your bytes by 2.

If you use BrnFck you can divide your bytes by 4 (let's get some recursion going here).

1 bit will be counted as 0.125 bytes (please put both in the title) so decimal byte scores are allowed.

Tags

brainfuck,code-golf,...

Answer 21

Program that allows the user to edit it's own source code

Write a program that displays and allows the user to view, edit and save it's own source code.

• If no edits are made, the output file should be the same as the program, and hence executing it should allow the user to edit the program's code again. (ie a quine)
• If the code has been edited in a sensible way, running the program again should display the edited code. The definition of 'sensible' is left flexible to prevent this being impossible - as the source code can be edited, a user can obviously edit the program in such a way that it no longer displays it's source code.

The standard quine rule applies: no reading the source file directly.

---

Additional Notes and things to consider:

• How robust is your program? What percentage of your program can be edited (sensibly) before it stops displaying it's own source or saving the edits you made.
• Both overwriting and saving with a different filename are valid ways for the program to save it's new code
• If it is a compiled language, the program does not have to invoke the compiler or do the compiling itself after saving.

• This is a code challenge not code golf. Robustness, interface and 'coolness' of the solution are favoured over brevity.

• Extra, uh, points(?!) if your program can identify errors in the quine before saving.

---

Is this a feasible challenge? Does it need clarification?

Answer 22

Prime Number Locator

Given a prime number p > 1, determine at what index p appears in A000040.

• You may 0 or 1 index, meaning 2 can return 0 or 1.
• If you are given a non-prime number you must return -1.
  • If you are 1-indexing you may return 0 instead, or still return -1.
• Your time complexity must be less than O(n): Please explain your calculations in the answer.

First 10 return values (0-indexed):

[2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
[0, 1, 2, 3,  4,  5,  6,  7,  8,  9]

This is code-golfrestricted-complexityprime: Reduce your byte-count to win.

Answer 23

Do the line segments cross?

Description: Today, we're going to do some geometry: We have two line segments and want to find out where they cross! A point is a pair of two integers being the x and y coordiantes of said point. If your calculations result in non-integers, you continue with the integer closest to your result.

I/O: You are given the two segments in form of 8 integers representing the 4 end points. You may take them in the order that fits you best, but you have to state the ordering. The output consisting of the point where the lines intersect, or null, an empty string or something similar, but no undefined behavior. You may use STDOUT, a file etc. to write your output.

This is code-golf - the shortest answer in bytes wins!

Answer 24

code-golf ...?

Fork for n times

TL;DR: fork up to n times, than hang forever

Relevant chat discussion

Your challenge is to make a program / function that calls itself twice or uses some other method of creating copies of itself that create copies of itself, etc.

However, to avoid crashing the system, your program limits itself before it forks to death. Given an input n, your program should stop forking when it has n total copies of itself (including itself), and keep running forever with n total copies of itself.

---

Meta

• Under-specified?
• Is the min of 500 good?
• Tags?
• Better title?

Answer 25

code-challenge regex [tag:H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝S̨̥̫͎̭ͯ̿̔̀ͅ]

Parse HTML with regex!

Alternate titles:

RegEx match open tags except XHTML self-contained tags

H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝S̨̥̫͎̭ͯ̿̔̀ͅ - Parse HTML with regex

Background

Don't parse HTML with regex. It always fails and sometimes summons Cthulhu.

But, because PPCG is different, we will parse HTML with regex.

And not easy, beginner HTML. HTML with comments, attributes with no quotes, HTML in script tags not commented out and much more. Can you write a regex to parse that?

The challenge

Your challenge is to make a regex that matches valid HTML tags. Don't match comments, don't match invalid HTML, don't match HTML in comments, just match valid HTML tags. Each full regex match is one HTML tag.

Your input HTML will never contain commas. You will try to get the most points possible by successfully matching the HTML tags and not the text in as many inputs as possible. Whoever gets the most points wins. Please say at least 1 regex flavor that your regex works with.

You are not allowed to use regex features to execute language code. (Sorry, Perl)

The length of your regex is irrelevant, this is not code golf.

Test cases

Here are the test cases. You can also find them at https://hastebin.com/raw/mikaxakipe.txt.

1,1,<b>HTML!</b>,<b>,</b>
2,1,<i><b>HTML</b></i>,<i>,<b>,</b>,</i>
3,1,a < b implies b > a,
4,2,<img alt=text>Img,<img alt=text>
5,2,<a href = "http://example.com">Example Domain</a>,<a href = "http://example.com">,</a>
6,2,<hr><br/>,<hr>,<br/>
7,2,<div id ="hi" class="what">What</div>,<div id ="hi" class="what">,</div>
8,3,<a>fake</>,<a>
9,3,Self-closing <img src = "self-closing.jpeg" />?,<img src = "self-closing.jpeg" />
10,3,<self-closed/>O_O<unclosed>,<self-closed/>,<unclosed>
11,3,Do<yOU>like<LoTs>of<mIXeD><cAsE>?,<yOU>,<LoTs>,<mIXeD>,<cAsE>
12,3,Wh<a b='c'd="e">at?,<a b='c'd="e">
13,3,Hi<p data-hi=3>hihihi</p>,<p data-hi=3>,</p>
14,4,<a"oops">Oops,
15,5,<!-- <b><!--hi--><i>,<i>
16,5,<0>NOT VALID</0><h0>fine</h0>,<h0>,<h0>
17,5,<a a=b<>what</a>,<a a=b<>,</a>
18,6,<!-- <b><!--hi--><i>-->,<i>
19,7,<how><deep can><your nesting nesting><level></level></go>?<how>Deep</how><can><your>nesting <go x=? j><how><deep can><your nesting nesting><level></level></go>?<how>Deep</how><can><your>nesting <go x=? j><how><deep can><your nesting nesting><level></level></go>?<how>Deep</how><can><your>nesting <go x=? j></your></can></your></deep></how></your></can></your></deep></how></your></can></your></deep></how>,<how>,<deep can>,<your nesting nesting>,<level>,</level>,</go>,<how>,</how>,<can>,<your>,<go x=? j>,<how>,<deep can>,<your nesting nesting>,<level>,</level>,</go>,<how>,</how>,<can>,<your>,<go x=? j>,<how>,<deep can>,<your nesting nesting>,<level>,</level>,</go>,<how>,</how>,<can>,<your>,<go x=? j>,</your>,</can>,</your>,</deep>,</how>,</your>,</can>,</your>,</deep>,</how>,</your>,</can>,</your>,</deep>,</how>
20,7,<plaintext><b></plaintext>,<plaintext>,</plaintext>
21,7,What<img src="imgs/>lolz.png" alt = "<heh"/>,<img src="imgs/>lolz.png" alt = "<heh"/>
22,7,<b><a href = "#" title = "4 > 3">hi</a></b>,<b>,<a href = "#" title = "4 > 3">,</a>,</b>
23,10,<StYle><b title = "not in html"></style><B>HTML!</b><style></style>,<StYle>,</style>,<B>,</b>,<style></style>
24,10,<script>//<script>< /script></script><script></script><p>,<script>,</script>,<script>,</script>,<p>
25,10,<i></i this="will be removed by a browser">,<i>,</i this="will be removed by a browser">
26,10,<div id="hi" class=class="what" data-the="heck='is'this" get-good>Attributes are weird<div>,<div id="hi" class=class="what" data-the="heck='is'this">,<div>
27,10,<!--<b>Do you like comments??</b>--><p>,<p>
28,13,<textarea><script>/* *////*///*<!--</script><b>WHAT</b></textarea><i>Hi-->,<textarea>,</textarea>,<i>
29,15,<!--<b>Do you like comments??</b><script>--><script>//<!--hello</script><b>hi</b><!--What--><script>//<!-- <script> <!-- <script> --> </script><i>hello--><script></script>,<b>,</b>,<script>,</script>,<i>,<script>,</script>
30,15,<hi>hi</hi><0>hi</0><h0>hi</h0><h&>hi</h&><&>hi</&><??>hi</??><?php>hi</?php><php?>hi</php?><->hi</-><_-_>hi</_-_><h->hi</h-><_>hi</_><h-_>hi</h-_><?>hi</?><{>hi</{><h{>hi</h{></>hi<//><h~!@#$%^&*()>hi</h~!@#$%^&*()><h>hi</h><h~>hi</h~><h!>hi</h!><@>hi</@><h@>hi</h@><h!@#$%^&*()>hi</h!@#$%^&*()><@f>hi</@f><%>hi</%><;>hi</;><h>>hi</h>><h&>hi</h&><h~>hi</h~>,<hi>,</hi>,<h0>,</h0>,<H&>,</H&>,<PHP?>,</PHP?>,<h->,</h->,<H-_>,</H-_>,<H{>,</H{>,<H~!@#$%^&*()>,</H~!@#$%^&*()>,<H>,</H>,<H~>,</H~>,<H!>,</H!>,<h@>,</h@>,<h!@#$%^&*()>,</h!@#$%^&*()>,<H>,</H>,<H&>,</H&>,<h~>,</h~>
31,30,<hi>hi</hi><0 WHAT_is=HtMl>hi&<i attrubute="oops'></0><h0 attRiBu350Te="<b>oops</b><style>/*">hi</h0>*/<h&>hi</h&><&>hi</&><??>hi</??><?php>hi</?php><php?>hi</php?><->hi</-><_-_>hi</_-_><h->hi</h-><_>hi</_><h-_>hi</h-_><?>hi</?><{>hi</{><h{>hi</h{></>hi&<//><script>     &/*<h~!@#$%^&*()>*/</ script></StyLe>/*</ScrIPT>/*<b>oops</b>hi</h~!@#$%^&*()><h>hi</h><h~>hi</h~><h!>hi</h!><@>hi</@><h@>hi</h@><h!@#$%^&*()>hi</h!@#$%^&*()><@f>hi</@f><%>hi</%><;>hi</;><h>>hi</h>><h&>hi&</h&><h~>hi/*/</h~><b>oops</b>hi</h~!@#$%^&*()><h>hi</h><h~>hi</h~><h!>hi</h!><@>hi</@><h@>hi</h@><h!@#$%^&*()>hi</h!@#$%^&*()><@f>hi</@f><%>hi</%><;>hi</;><h>>hi</h>><h&>hi&</h&><h~>hi/<script></StyLe></ScrIPT><textarea><b>HE COMES</b></textarea><h!>hi</h!><@>hi</@><h@>hi</h@><h!@#$%^&*()>hi</h!@#$%^&*()><@f>hi</@f><%>hi</%><;>hi</;><h>>hi</h>><h&>hi&</h&><h~>hi</h~>,<hi>,</hi>,<i attrubute="oops'></0><h0 attRiBu350Te="<b>,<style>,</style>,<textarea>,</textarea>,<h!>,</h!>,<h@>,</h@>,<h!@#$%^&*()>,</h!@#$%^&*()>,<h&>,</h&>,<h~></h~>

Each line is a separate test case. They are in this format:

1,1,<b>HTML!</b>,<b>,</b>
| | |            |   |
| | |            +---+- The correct output: all HTML tags in the string separated by commas
| | +- The HTML for you to parse
| +- The number of points you get if you parse this HTML correctly
+- The test case number

Example

Let's say we have the regex /<.*?>/g (all flavors). For test case #1, it matches 2 times: <b>, and </b>. The correct output in the test case says that it should match <b> and </b>, so it is correct. Our regex gets 1 point.

Then for test case #2. Our regex matches <i>, <b>, </b>, and </i>, which is consistent with the test case so we get 1 point.

Now for test case #3. Our regex matches < b implies b >, when it should have not matched anything. We get 0 points for that.

Continuing for each test case gets us a score of 50 (out of 207, or 24.15%). Not great. Can you do better?

Try It Online

If your regex will work with the ECMAScipt / JS flavor than you can try it here and get automatic scoring!

Tie breaker

Here are the scoring systems. Whoever has the best score on the first wins. In the event of a tie, whoever out of the ties scores the best wins, etc.

1. Most points
2. Shortest length
3. First posted

Answer format

[insert score here] / 207 points

[insert regex here]

Explanation (optional but encouraged)

Proof of score (matched output vs. test cases, link to TIO to try it, etc.)

---

Meta

• Dupe? (I don't think so)

Answer 26

Matrix Decomposition

matrix array-manipulation code-golf

Meta

• Duplicate?
• What rules should I add?
• Are my explanations sufficient?
• Any room for improvement?

It's possible to "factor" any invertible (a.k.a. non-singular) square matrix A into a combination of a permutation matrix¹ (P), a unit³ lower triangular matrix² (L), a diagonal matrix⁴ (D), and a unit upper triangular matrix² (U).

That is, A = PLDU

For instance, the matrix [[4, 5], [2, 3]] can be expressed as the multiplication of the following matrices:

P = [[0, 1],
     [1, 0]]
L = [[1, 0],
     [2, 1]]
D = [[2, 0 ],
     [0, -1]]
U = [[1, 3/2],
     [0, 1  ]]

Task

Given an invertible square matrix A, output P, L, D, and U.

Test Cases

TBD

Rules

• Any reasonable output format is acceptable, but P, L, D, and U must be separate outputs.

---

^{1. A permutation matrix is a permutation of the identity matrix.}

^{2. An upper triangular matrix is a square matrix whose nonzero values occur only on or above the main diagonal, and a lower triangular matrix is a matrix whose nonzero values occur only on or below the main diagonal.}

^{3. A unit triangular matrix is a triangular matrix whose main diagonal is all 1s.}

^{4. A diagonal matrix is a matrix whose nonzero values occur only on the main diagonal.}

Answer 27

Become a Word-Pontif

The french used to define the word pontif as one who builds bridges stemming from the conjunction of pons, facere which literally translates to a bridge, to create one. Your task will be, given a list of 1 or more lower-case words l (String Array), output the MAXIMUM length of a bridge that can be built from these words.

---

Bridge Rules

• Bridges can be made by connecting two or more words together:
  • Words must be connected prefix-to-suffix or suffix-to-prefix.
    • To join two words into one:
      • The suffix of the first must match the prefix of the second (abc+cba=abcba).
      • The prefix of the first must match the suffix of the second (earl+toe=toearl).
  • If a word's prefix/suffix contains more than one common character:
    • You can only connect them with the maximal common substring.
    • In other words,abc and bcdefg can be connected using a[bc]defg.
• The length of a bridge is simply the length of the conjoined words in characters.

---

Building Material Rules

• The list will contain at fewest 1 word.
• The list may hold 0 links between words, in this case the maximal size is the longest word in the list.
• The list will not contain the empty string and will only use the lowercase alphabet (a-z).
• The list MAY NOT contain duplicates.

---

Examples

Example 1:

[abcdefgh,holographic,graphical,quine,loitering]

abcdefholo[graphic]al = 19

19

Example 2:

[noon,moon,loon,noon,groom]

groo[m]oon

8

Example 3:

[spoon,whatifgodwereoneofus,oneofusisatraitor,aaaaaaaaaaaaaa,aaaaaaaaaa]

whatifgodwere[oneofus]isatraitor (because the two aaaaa's overlap too much).

30

Example 4:

[abc,def,ghi,jkl,mnop,qrst,uvwxyz]

uvwxyz (No matches)

6

Example 5:

[xox,xxox,lol,lolol,lololol,xoxx]

xo[xx]o[x]ox    < 8  (Maximal of the xox path)
[lol]o[l]ololol < 10 (Maximal of the lol path)

10

Example 6 (Base):

[hi]

hi

2

Example 7:

# Note, when a link has been used it cannot be used twice.
# In other words, the brackets used cannot overlap in these examples.
[aa,aaa,aaaa] 

aa[aa][a]a (Chose to use aaaa,aaa,aa)

7

---

General Rules

• This is code-golf, lowest byte-count wins.

Answer 28

Word Grid Pathfinding

A follow up to Generating Word Grids and Validating Words in Word Grids.

---

Meta

My original idea for this was to have entries compete, but I'd like to have different winning conditions. Given grid x, pit all scripts against each other for the following win criteria:

• Highest Score
• Shortest Path
• Fewest remaining tiles
• Longest Words

but I think perhaps just making it code golf and offering a bounty to each of the criteria above after some time. I'd like some feedback on this. I like @LegionMammal978's idea, but feel like perhaps that could be a separate challenge (again, only if these are interesting to anyone!)

---

Given a grid of letters, complete a path of words that reaches from the centre of the board, to the edges. You must return lists of your moves as co-ordinates and your score will be tallied. As soon as there is a clear path from the centre to the edge, the game is over, and no further words will be scored.

Details

Grids will always have an equal, odd, number of rows and columns, such that no direction contains fewer tiles.

Restrictions

In the event that the grid is unsolvable (or becomes unasolvable because of your chosen path, you may return something falsy instead of a list of co-ordinates.

Your script must be able to handle grids of varying sizes and solve them in a reasonable time, such that a service like TIO can be used, without causing problems in most cases, for extremely large inputs (> 500). You are free to take input in any reasonable format, but please include a link to your script with a wrapper such that it can take input in via STDIN/script arguments via an online service.

#TODO: copy details of the adjacency rules from above.

For example, in the grid provided below, the J, I, P or O letters (north, east, south and west of the blank square) must be included, once this word has been removed, you have more available words.

There are bonus letters that provide a double point score, denoted by a lowercase letter or ! (instead of ? for a blank tile). Blank tiles are used exactly as they are in Scrabble and can count as any letter, the validating program will search for words replacing the ? (or !) with a wildcard. Letters are scored as per Scrabble:

0 points: blank tiles
1 point: E, A, I, O, N, R, T, L, S, U
2 points: D, G
3 points: B, C, M, P
4 points: F, H, V, W, Y
5 points: K
8 points: J, X
10 points: Q, Z

Your score will be calculated by the validator.

Examples

Input:

UWDESTKP?
ItDBaDEdI
TERMDYTSR
ROANJLEFT
EkCI OOsT
IPAJPGMNY
MZLORITVI
GwEGgPUeI
MNROYOEER

Output:

6,4 6,5 5,5 4,5 3,5 3,6 2,6 1,6
5,6 4,6 4,7 4,8

Total moves: 2
Points: 21

#TODO: more examples.

Answer 29

Shift-left golfer

Sometimes when doing code-golf, a person needs to understand which format is shorter:

• 2147483648
• 0x80000000
• 1<<31

The task:

You will receive a number in one of the three formats above: decimal, hexadecimal, or shift-left operation. If there is no advantage in converting it to another format, just leave the number the way it is; otherwise I want the shortest format. Of course there are numbers you can't convert to shift-left format!

Notation:

• Hexadecimal — 0x#######.... where there are no leading zeros after the x. When accounting for evaluating the golfiness, the 0x part is also taken into consideration. For example 0x80000000 has a length of 10.

• Decimal — #######.... where there are no leading zeros.

• Shift-left — #...<<#.... no leading zeros both sides of <<. The << operator is also considered for length, e.g 1<<31 has a length of 5. You must also handle multiple digits before the << signal.

# represents a digit and ... represent possible repetition of digits

I don't care if you handle leading zeros at the input or not; but if you handle them, you must do the comparison operations without them and output also without them — You're a golfer, come on! You will understand!

There will be no accepted answer.

code-golf, so I want to know shortest answer by language.

UPDATE 1:

In spite of @dzaima 's comment, now it also needs to handle multiple digits before << signal.

Answer 30

Translate Tetris moves to GoL!

code-golf

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Unless you've been living under a rock, you're probably aware of the fact that the highest voted unanswered, incredibly hard challenge to build a working game of Tetris in Conway's Game of Life just recently got answered. (Go check it out if you haven't already.)

Unfortunately, since this game is written in Conway's Game of Life, giving input to the code is a bit tricky. (Of course, if they can simulate Tetris in GoL, you can play it with tricky moves. :P) To quote the main answer:

Each move only requires editing a single bit of RAM, and this input register is automatically cleared after the input event has been read.

Each Tetris move corresponds to a single number by the following table:

value     motion

1         counterclockwise rotation
2         left
4         down (soft drop)
8         right
16        clockwise rotation

Now, of course, if there was only a way to automate this...

Challenge

Write a program/function that takes a series of keypresses as input and outputs each keypress' respective number according to the table above.

The keypresses should map as the following:

value            motion

<                counterclockwise rotation
<left arrow>     left
<down arrow>     down (soft drop)
<right arrow>    right
>                clockwise rotation

Specifications

• Standard I/O rules apply.
• Standard loopholes are forbidden.
• This challenge is not about finding the shortest approach in all languages, rather, it is about finding the shortest approach in each language.
• Your code will be scored in bytes, usually in the encoding UTF-8, unless specified otherwise.
• Built-in functions that perform this task are allowed but including a solution that doesn't rely on a built-in is encouraged. (Pshh, how likely is that?)
• Explanations, even for "practical" languages, are encouraged.

Test cases

// incoming

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Sandbox

• Should I switch from keypresses to strings of ( < v > )?
• I'm really lacking on tags...
• Bump!