# What is the Sandbox?

This "Sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to the main page. This is useful because writing a clear and fully specified challenge on the first try can be difficult. There is a much better chance of your challenge being well received if you post it in the Sandbox first.

See the Sandbox FAQ for more information on how to use the Sandbox.

## Get the Sandbox Viewer to view the sandbox more easily

To add an inline tag to a proposal use shortcut link syntax with a prefix: [tag:king-of-the-hill]

# What's Underneath the Sine Wave?

Your task is to output a part of the sine wave out of any characterss of your choosing and on any background of your choosing. The wave can start and end either on the highest or the lowest point of the wave if both are the same.

The challenges main part is what happens below the wave (or above if you chose to start at the peaks of the wave). For each column, looking top-to-down it should repeat until the bottom the segment of spaces until the wave.

### Or a visual explanation:

Start with a sine wave of your choosing (this is not a valid one as it isn't 50x20, but smaller to save space):

             ####
##    ##
#        #
#          #
#            #
#              #
#                #
#                  #
#                    #
##                      ##
##                          ##


and then, look top-down and until the 1st encounter of a non-background character record the characters and then repeat them:

        ↓   ↓####
↓  ##  P ##
4x↓ # ↓  P   #
↓#  P  P    #
X   ↓  P     #
#↓   P  P      #
# ↓4x ↓  P       #
#  ↓   P  P        #
#   ↓   ↓  P         #
##    P   P  P          ##
##      ↓   ↓  P            ##


so for this the output would be

             ####
########
#  ####  #
# ######## #
#    ####    #
#  ##########  #
#      ####      #
#   # ######## #   #
#     #  ####  #     #
##    #  ########  #    ##
##           ####           ##


## Clarifications

• There can be any amount of leading/trailing lines with any amount of whitespace
• On each line there can be extra leading whitespace, as long as the amount is equal on all lines
• The width should be at least 50 characters total (excluding columns of only whitespace)
• The height should be at least 20 characters total (excluding lines of whitespace only)
• The repeating bottom parts must be cut from the bottom (or top) of the wave
• Inaccuracies due to rounding or floating-point errors can be dismissed
• The background character has to be constant
• The wave characters can be different, as long as they aren't ever equal to the background
• This is , the shortest code per language wins!

## Sample outputs

                         XXXXXX
XXXXXXXXXX
XX  XXXXXX  XX
X  XXXXXXXXXX  X
X     XXXXXX     X
X  XXXXXXXXXXXXXX  X
XX       XXXXXX       XX
X    X  XXXXXXXXXX  X    X
X      XX  XXXXXX  XX      X
X     X   XXXXXXXXXX   X     X
X            XXXXXX            X
X      X XXXXXXXXXXXXXXXX X      X
X              XXXXXX              X
X      XX     XXXXXXXXXX     XX      X
X          X XX  XXXXXX  XX X          X
X       X    X  XXXXXXXXXX  X    X       X
X                  XXXXXX                  X
XX        X   X  XXXXXXXXXXXXXX  X   X        XX
X                     XXXXXX                     X
XXX          X     XX  XXXXXXXXXX  XX     X          XXX

..................................................
DCB....................QPONM....................10
...A9........0.......SRQPONMLK.......C........32
.....8..........X...T..QPONM..J...F..........4
......7.......Z...VU.SRQPONMLK.IH...D.......5
.......6...............QPONM...............6
........5......Y.W..TSRQPONMLKJ..G.E......7
.........4.............QPONM.............8
...................U.SRQPONMLK.I
..........3.......V.T..QPONM..J.H.......9
...........2....X....SRQPONMLK....F....A
............1..........QPONM..........B
.................W.UTSRQPONMLKJI.G
.............0.........QPONM.........C
..............Z...V..SRQPONMLK..H...D
...............Y....T..QPONM..J....E
...................U.SRQPONMLK.I
................X......QPONM......F
.................W..TSRQPONMLKJ..G
..................V....QPONM....H
...................U.SRQPONMLK.I
....................T..QPONM..J
.....................SRQPONMLK
.......................QPONM..................................
...
.
....


# sandbox

• please suggest (or just edit in) ways of making this clearer
• Anything missing?
• Should I make this challenge take input, rather than being an broad kolmogorov-complexity challenge?
• Is the sample output for input X? – officialaimm Jul 3 '17 at 12:27
• @officialaimm The characters can be of your choosing, there's no input currently – dzaima Jul 3 '17 at 12:27
• So, all the positions marked by X should have same character or can have different characters? – officialaimm Jul 3 '17 at 12:40
• @officialaimm They can have any characters – dzaima Jul 3 '17 at 12:42
• I think its better if you showcase sample output with different characters then. – officialaimm Jul 3 '17 at 12:53
• I can't tell what the task is from reading the description, or from looking at the example. It might help to walk through a few example columns to make it clear, then follow up with the full wave examples after that. – trichoplax Jul 17 '17 at 14:12
• @trichoplax good idea – dzaima Jul 17 '17 at 14:12
• Thanks. A second look at the examples was enough for me to grasp the pattern, but a step by step example would probably have got it across quicker. – trichoplax Jul 17 '17 at 14:14

# Pristine Pristige

A pristine program, as defined by Calvin'sHobbies, is

a program that does not have any errors itself but will error if you modify it by removing any contiguous substring of N characters, where 0 < N < program length.

Pristige is a language I designed in which all syntactically valid programs are pristine.

Pristige works just like Brain-Flak, except every function requires a airity declaration at the beginning. An airity of n is declared with n .s followed by a |. For example the Brain-Flak program

({}())


Is equivalent to the Pristige Program

(..|{|}(|))


In addition Pristige requires that there is only one function at the top level of the program. Meaning that

(.|{|}){.|(..|{|}[.|(|)])}


Is an invalid program.

To be absolutely concrete here is a grammar that spans all syntactically valid Pristige programs:

S → (A) : <A> : {A} : [A]
A → .AS : |


You must write a compiler from Pristige to Brain-Flak, that is itself a pristine program.

This is a question so answers will be scored in bytes, with less bytes being better.

## Rules

• You must either throw an error (or print error if your language cannot do so) if the inputted program is syntactically invalid.

• If the input is syntactically valid you must output an equivalent Brain-Flak program. The simplest way to do this is to remove all instances of . and |, but you are not required to do so.

• You may use any default IO format.

• Your program must be a pristine program. That means deleting any continuous substring must cause an error

## Reference Implementation

Here will go an implementation I have not yet completed

## Test Cases

Here will go test cases

• Surely we should print error if the program is syntactically invalid? Sort of unrelated, but is Pristige a mix of the words pristine and prestige? – FryAmTheEggman Jul 17 '17 at 19:25

# Write a code poem programming-puzzlepopularity-contest

It is said that Larry Wall, creator of Perl, wrote a poem titled "Black Perl" in said language, as shown here.

The poem is fully functional (working syntax, no runtime errors, etc. [no errors in general]).

# The challenge:

In any language (practical languages recommended), write a haiku (example of one at https://en.wikipedia.org/wiki/Haiku).

# Coding rules:

• The poem must be able to function properly (no errors).
• Unlike Wall's poem, you must run through the whole program (exits only at the end).
• If you define a function to act as a word, it will count towards your poem.
• Caught errors and other error-handling tricks are valid.

# Misc rules:

• You cannot use multi-line strings or line continue symbols, etc. (No multi-line functions/tricks).
• Brackets, parentheses, and other grouping symbols (with the exception of < and > as operators are ignored unless as a string.

# Example lines (written in Python, not the best, probably):

while i_love ....: # i_love counts as two words

i_am > than_you # read symbols/operators as words

"""my love for ...
is ....... by ...""" # Invalid, as stated by one of the misc. rules

me(,"john", "abby",
"and liz") # invalid, line continuation


# Winning:

This is a , so submission with the highest amount of votes wins.

# For sandbox only:

How can I improve on this challenge? Is there anything else I should add? Let me know in the comments.

• This is currently both too broad and unclear. What does "work" mean? What is a "script"? What is allowed besides "words" (whatever those are)? How do we measure answers against each other? Try to look at some of the challenges on this site to get a better feel for what we do here - I'm afraid this is very far off the mark. You can try asking other users in chat, once you get some reputation, about ways to make this fit better, but personally I don't think this kind of challenge is a good fit for this site. – FryAmTheEggman Jul 17 '17 at 19:35
• I like the idea, but I think you need to be more specific in what is valid and invalid. If my script is just one giant multi-line string, it satisfies your requirement, but obviously that's not what you're going for. – wrymug Jul 17 '17 at 19:37
• Will edit the question. – S.G. Harmonia Jul 17 '17 at 19:37
• Are caught errors allowed? – wrymug Jul 17 '17 at 20:38
• You mean stuff like try? – S.G. Harmonia Jul 17 '17 at 20:57
• Who wins? What's the criterion for deciding that? – Rɪᴋᴇʀ Jul 17 '17 at 21:32
• @Riker I am currently thinking about that. – S.G. Harmonia Jul 17 '17 at 23:07
• @S.G.Harmonia yeah – wrymug Jul 18 '17 at 0:05
• I do think this question might be too broad. Maybe make it so it has to be a haiku? And then score by popularity contest – wrymug Jul 18 '17 at 0:07
• 1. I have no idea where to close the parenthesis in "Brackets, parentheses, and other grouping symbols (with the exception of < and > as operators are ignored unless as a string.". 2. A popularity contest should have a clear spec to identify valid answers, and an indication of what aspect of the answers makes them good. It's a hack to judge subjective contests like codegolf.stackexchange.com/q/33172 . I don't think this has a clear spec ("Don't produce an error" is far too broad), and it's not clear what makes a haiku program a good haiku program? – Peter Taylor Jul 18 '17 at 7:35
• As an illustration of the problems raised in point 2, consider that I can take any haiku I want, remove the characters ,.+-<>[] (of which only the first two are likely to be present anyway) and claim it's a brainfuck program which does nothing. And before you edit to add a rule to prohibit that directly, let me emphasise the word illustration. The problem is far deeper, and I don't think it can be fixed. It certainly can't be papered over. – Peter Taylor Jul 18 '17 at 7:37

### Challenge

Take a number and output it with 4 digits or less using letters and numbers. For example; 270,030 would turn into 2.7K.

### Key

Billion -> B

Million -> M

Thousand -> K

### Rules

• You may choose to accept input numbers that include commas delimiting every three decimal places (such as 123,456,789).
• Round to nearest, half-up.
• Numbers will only go up to a trillion.
• The mantissa part of the answer should be at least 1.
• All letters must be uppercase and as specified below.
• Outputs must be 4 or less characters wide.
• Outputs must be as mathematically precise as possible. Example:
• 154,893 -> 100K NOT OK
• 154,893 -> 155K GOOD
• If there are multiple outputs with the same mathematical precision, return the shortest one. (If they are the same length, you may return either.) Example:
• 1000 -> 1000 NOT OK
• 1000 -> 1K GOOD

### Examples:

1,234,567 -> 1.2M
102 -> 102
1000 -> 1K
1001 -> 1001
100,000 -> .1M
12,345,678,912 -> 12B
1,452,815,612 -> 1.5B


### Submissions

• I made a bunch of edits, feel free to roll back any changes you dislike. For the case of 100,000, should you return .1M, 0.1M, or 100K? – musicman523 Jul 15 '17 at 23:39
• I like 100K best, maybe we should change it to 5 or less characters. Also thanks for the edits. – zoecarver Jul 15 '17 at 23:41
• Personally I think 4 characters is fine. To further elaborate on my question: If you are outputting a decimal, do you require a leading 0 or would you allow .1M? – musicman523 Jul 15 '17 at 23:46
• I think .1M should be 100K and we should allow up to 4 digits (or under 5). – zoecarver Jul 15 '17 at 23:47
• Oh, I thought it was 4 digits or less. My misunderstanding. If .1M is not allowed then you should clarify in the question that the "number" part of the answer should be at least 1. However this seems rather arbitrary to me, when your original goal was to get the number as short as possible – musicman523 Jul 15 '17 at 23:49
• Ok, I will specify. thanks for the help! – zoecarver Jul 16 '17 at 0:36
• 1. The ""number"" part is called the mantissa. 2. I think "as specified below" should be "as specified above". 3. 154,894 -> 1.5K is not GOOD. It should be 155K. 4. Or should it? I don't see any rules specifying how to round. 5. 1K has less precision than 1000 because it gives fewer significant figures. – Peter Taylor Jul 16 '17 at 7:05
• Thank you for your feedback! I have applied your edits, anything else? – zoecarver Jul 18 '17 at 3:29
• I am going to post this unless anyone has any other feedback. – zoecarver Jul 19 '17 at 19:32

# Bastion Breach

Stolen with permission from the minigame with the same title from Angels with Scaly Wings

## Introduction and rules

• There are two players
• Both players receive a suit of cards (2-9, ace and face cards) and another is randomly shuffled into a public zone.
• The players then proceed to choose one of the cards in their hand to bid for the card. Once they've used a card, it can't be used again.
• The owner of the card with the highest value then gets a point.
• If the highest scoring card was in the middle or if the value of the highest cards is equal, nobody gets a point. That point then goes onto the next round and is awarded to the winner of that round.
• The ace is special: it wins against a face card, ties with another ace, and loses against a number card. Effectively the scoring system is reversed for the ace card.
• The player with the most points at the end of the game wins.

## Input/Output format for bots:

At the beginning of each round, your bot will be called as a whole program and will receive input in the form cards-in-middle your-played-cards opponents-played-cards as command line arguments.

Example: 23456789JKQA 24 56 - The cards in the middle are 23456789JKQA, your played cards are 24 and your opponents are 56. Your opponent won both of the previous games and what you're bidding for is the card 4.

You will output a single character representing a card that you haven't already played. If it is invalid or you've already played it, you automatically forfeit the round. Valid outputs are the following characters: 23456789JQKA

## Example scoring

Middle card: 2
Bot 1 card: 4
Bot 2 card: 5
Winner: Bot 2
----
Middle card: Q
Bot 1 card: K
Bot 2 card: 5
Winner: Bot 1
----
Middle card: Q
Bot 1 card: K
Bot 2 card: A
Winner: Bot 2
----
Middle card: Q
Bot 1 card: 6
Bot 2 card: 5
Winner: None, next round scores another point
----
Middle card: A
Bot 1 card: 2
Bot 2 card: J
Winner: Bot 1
----
Middle card: 5
Bot 1 card: K
Bot 2 card: 5
Winner: Bot 1
----
Middle card: 5
Bot 1 card: 2
Bot 2 card: 5
Winner: None, next round scores another point
----
Middle card: A
Bot 1 card: 9
Bot 2 card: J
Winner: None, next round scores another point


Scoring for regular cards: 23456789JQK

Scoring for the ace:

wins: JQK
draw: A
lose: 23456789


## Submission

You should write your entry as

Bot Name, Language

Insert
Code
Here


Explanation/Random stuff here

## Running the tournament yourself

The controller is available here (Sandbox: Not written yet). It can be ran with python3 controller.py or python controller.py depending on your path. It expects all the bots to be in the bots directory. You can get all the bots already entered with python get_answers.py or python3 get_answers.py

## Other rules and information

• Bots are not allowed to use file storage.
• The competition will be Round Robin, all bots will play against all others and they will be ranked by the number of other bots they've won against.

• A loss counts as nothing
• A draw counts as one point
• A win counts as two points
• The bot with the most points wins the game.

• The bot that wins the final game, to be ran on wins the tournament.

### Sandbox notes:

• I have yet to create a controller for this though I'll probably be basing it off the one I did for the cake cutting contest
• I hope I've explained it well enough, it's a simple game and I want the barrier for entry as low as possible. I've tried fixing what I believe went wrong with the GOL challenge and feel that KOTHs work better when they have lots of bots.
• I have permission to post this from the developer of the game in question, see first line.
• Feedback on readability is very much appreciated and welcome
• "Both players receive a suit of cards (2-9, ace and face cards) and another is randomly shuffled into a public zone. The players then proceed to choose one of the cards in their hand to bid for the card." Which card? Reverse engineering from the example, I think that what's meant is that the third suit is uniformly shuffled and dealt face up in a line, such that both players can see the entire sequence of auctions, and then the cards are auctioned off one by one from left to right. Future references to "the middle" are presumably references to the same "public zone"? – Peter Taylor Jun 29 '17 at 11:34
• "The ace is special: it wins against a face card, ties with another ace, and loses against a number card." Unless I'm missing something, there's nothing special there: just an overcomplicated abstraction. On the basis of KISS I would suggest making the cards be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or A, B, C, D, E, F, G, H, I, J, K, L, M. – Peter Taylor Jun 29 '17 at 11:36
• The ace card is different in that it's scored in reverse compared to the other cards. And your first comment is correct, how would you suggest rewording for it to be more clear? – Blue Jun 29 '17 at 15:31

# What's that character? (Part 1) code-golf

Recently I ran a command on my laptop that returned a bunch of characters - some printable, some non-printable. I'm having trouble figuring out what those characters are, so I could use some help. Unfortunately, I'm running low on disk space, so you'll have to write me the shortest program you can that I can run.

# Challenge

Given a list of ASCII characters, return their names as written on www.asciitable.com, my go-to site for looking up character points.

### Input

You may take a string, a list of characters, or a list of ASCII code points (e.g. 'a' -> 97).

You may optionally take the length of the string/list as well. Note that for C, you must take this parameter, since the string could contain NUL bytes, so strlen won't work here.

### Output

Output is flexible as usual; you may print or return from a function as you see fit. You should output a list of strings.

### The Table

0 NUL
1 SOH
2 STX
3 ETX
4 EOT
5 ENQ
6 ACK
7 BEL
8 BS
9 TAB
10 LF
11 VT
12 FF
13 CR
14 SO
15 SI
16 DLE
17 DC1
18 DC2
19 DC3
20 DC4
21 NAK
22 SYN
23 ETB
24 CAN
25 EM
26 SUB
27 ESC
28 FS
29 GS
30 RS
31 US
32 Space
33 !
34 "
35 #
36 $37 % 38 & 39 ' 40 ( 41 ) 42 * 43 + 44 , 45 - 46 . 47 / 48 0 49 1 50 2 51 3 52 4 53 5 54 6 55 7 56 8 57 9 58 : 59 ; 60 63 ? 64 @ 65 A 66 B 67 C 68 D 69 E 70 F 71 G 72 H 73 I 74 J 75 K 76 L 77 M 78 N 79 O 80 P 81 Q 82 R 83 S 84 T 85 U 86 V 87 W 88 X 89 Y 90 Z 91 [ 92 \ 93 ] 94 ^ 95 _ 96  97 a 98 b 99 c 100 d 101 e 102 f 103 g 104 h 105 i 106 j 107 k 108 l 109 m 110 n 111 o 112 p 113 q 114 r 115 s 116 t 117 u 118 v 119 w 120 x 121 y 122 z 123 { 124 | 125 } 126 ~ 127 DEL  # Test Cases [0, 97, 7, 22] -> [NUL, a, BEL, SYN]  More to come... # Meta • Would it be more interesting to use the UTF-8 names for the printable characters (0x20 - 0x7E), and the ASCII names for the control characters? • hand copy the table from the website please dont. Try a Google search: theasciicode.com.ar/ascii-codes.txt – Stephen Jul 23 '17 at 22:39 • @StepHen good call, thanks – musicman523 Jul 23 '17 at 23:24 • Downvoter: I would much like your feedback rather than just your vote – musicman523 Jul 24 '17 at 1:39 • IMO just have take a letter and output the code. Since that part is boilerplate str.chars.map( real program ). Also for ASCII char names NUL is it ok is we output them in lower case? e.g. nul (obviously ascii letters would have fixed case) – Downgoat Jul 24 '17 at 1:42 ## How good is my mahjong hand? Your goal is to calculate the shanten (minimal number of tiles needed for your hand to be a "waiting hand") of a Riichi mahjong hand. What is Japanese Mahjong (or Riichi) The goal of the game is to build a 14 tiles valid hand. Your hand is 13 tiles long, and each turn, you draw a 14th. If it doesn't make you win, you discard a tile. The tiles are grouped by colors : man, numbers, let's call them m; pin, circles, p; sou, bamboos, s; and honor tiles, z. For p,m, and s : tiles are numbered from 1 to 9, with 4 examples each (1m 1m 1m 1m 2m 2m 2m 2m 3m 3m 3m 3m... 9m 9m 9m 9m). z contains winds : ton for east, e; nan for south, s; sha or xia for west, w; and pei for north, n. z contains dragons too : chun for red, r; haku for white, h; and hatsu for green, g. Same rule, 4 examples each. Honor tiles cannot be sequenced in a chii, they can only combine with themselves, by matching for a pair or for a pon. Don't worry, I will define terms pon and chii in the next part. So a random hand can look like 1s 1s 1s 2s 2s 2s 3s 9p 9p 4m ez ez nz. What is a "waiting hand" What is called a tenpai hand, or hand that is one tile left before winning, is a hand respecting a winning shape. In general, a winning hand is composed of 4 sets of 3 sequenced (chii, like 1s 2s 3s) or matching (pon, like 1s 1s 1s) tiles, plus a pair (like 1p 1p). An example of a winning hand (14 tiles) can be : 1s 2s 3s 4s 5s 6s 6s 7s 8s 3p 3p 3p ez ez So a "waiting hand" can be : 1s 2s 3s 4s 5s 6s 6s 7s 8s 3p 3p 3p ez where you need only ezto win. The goal To output a positive integer (between 0 and 7, inclusive) representing the shanten as defined above. For instance, a hand like 1s 1s 1s 2s 2s 2s 3s 9p 9p 4m ez ez nz is 2 shanten, because : - you have a set of three 1s (a pon) - you have a pon of 2s - you have a pair of 9p (your pair) - you have another pair of ez (that needs a third one to become a pon) - you have 3 "isolated" tiles, 3s,4m,nz. So drawing ez, and creating the pon of ez, makes you discard nz for example. Then let's imagine you draw 2s : you discard 4m, and you are now with a "waiting hand", with : 1s 1s 1s 2s 2s 2s 2s 3s 9p 9p ez ez ez, waiting on 1s or 4s. You drew two "useful tiles" to come to this hand, so you were 2 shanten. @Sandbox : Is it on-purpose to put two detailed examples? (pro : clarifies what you have to do / con : challenge's wall of text is even bigger) Another example Let's see your hand looks like 4p 5p 7p 1m 1m 1m 2s 4s 6s ez sz hz hz. - you have a pon of 1m - you have 4p and 5p sequenced, requiring 3p or 6p to be a chii - you have 2s 4s 6s, requiring 3s or 5s to create a chii - you have a pair of hz - you have 3 "isolated" tiles, 7p, ez and sz. So, as for the first example, we have 3 isolated tiles. But are we 2 shanten? No, because 2s 4s 6s is not complete. So in fact, we have 4 useless tiles, the 4th being 2s or 6s depending on what we draw. Proof : if we draw 3p, 3s and hz, our hand looks like that : 3p 4p 5p 1m 1m 1m 2s 3s 4s sz hz hz hz and is waiting on the second sz to form the pair and win. We drew 3 useful tiles, so we were 3 shanten. Test cases 3m 6m 9m 3p 5p 8p 1s 5s 8s ez sz nz gz -> 7 shanten 3m 6m 9m 3p 4p 5p 8p 1s 5s 8s ez sz nz -> 6 shanten 3m 6m 9m 3p 4p 5p 8p 1s 5s 8s ez nz nz -> 5 shanten 3m 6m 9m 3p 4p 5p 8p 8p 5s 8s ez nz nz -> 4 shanten 3m 5m 6m 9m 3p 4p 5p 8p 8p 5s 8s nz nz -> 4 shanten 3m 4m 5m 6m 3p 4p 5p 8p 8p 5s 8s nz nz -> 3 shanten 3m 4m 5m 6m 3p 4p 5p 8p 8p 5s 5s nz nz -> 2 shanten 3m 4m 5m 6m 7m 3p 4p 5p 8p 5s 5s nz nz -> 1 shanten 3m 4m 5m 6m 7m 3p 4p 5p 5s 5s nz nz nz -> 0 shanten 6s 7s 8s 1p 1p 1p 3p 4p 5p 6p 7p 7p 7p -> 0 shanten 3s 4s 5s 6s 7s 2p 4p 6p ez nz nz hz gz -> 3 shanten 3s 4s 5s 6s 7s 7s 1p 2p 4p 6p nz nz hz -> 2 shanten 3s 3s 4s 5s 6s 7s 7s 2p 4p sz sz nz nz -> 2 shanten 3s 3s 4s 5s 5s 6s 7s 7s 4p nz nz sz sz -> 2 shanten 3s 3s 3s 4s 5s 5s 7s 8s 2p 3p 4p 6p 6p -> 1 shanten 1m 1m 1m 2s 7s 7s 1p 3p 4p 9p sz hz cz -> 4 shanten 3m 6m 9m 3p 8p 1s 5s 8s ez sz nz gz cz -> 8 shanten  Protip Calculating shanten can be complex, so here is a link that can help you doing so. You can refer to this site if you need any other information on riichi mahjong. Good luck! Scoring and extra rules This is code-golf, so shortest answer in bytes wins for its language. Standard loopholes apply. NB : If you know mahjong, or were curious and dug deeper into the rules, don't mind with specific shapes like seven pairs or thirteen orphans. tags : @Sandbox : should I create some sort of in a pastebin or something? Related Related too Something that can help if you speak japanese <- you can copypaste in the field the output from this program :) Another protip SANDBOX Feel free to comment and tell me if this is on-purpose in PPCG, if there is any way to improve the way I say things, if I'm unclear anywhere ... • If you downvote, please explain why (by commenting or suggesting edit) so I can improve. If you don't, then don't downvote, this makes just the post less visible for no reason. – V. Courtois Jul 24 '17 at 6:17 • Didn't downvote this, nor have I read through it yet. But that may be the reason it just appears to be a wall of text. Maybe try splitting it up into multiple posts or breaking the text down into easier read chunks. Or even take bits out that might not be needed. – TheLethalCoder Jul 24 '17 at 8:28 • @TheLethalCoder in fact I'd like to explain clearly what is mahjong (to put some context in the challenge). Though you're right, it is a wall of text, that's what it looks like to me too. And I can't really "split it" into multiple posts, because it is what the challenge will look like in the end. TL;DR I want to be as clear as possible since this challenge is gonna be hard. – V. Courtois Jul 24 '17 at 8:32 • I think you should be able to make it clearer by tidying the post up and formatting it more. The problem is a lot of people will open the question see all the text and move on without giving it a chance – TheLethalCoder Jul 24 '17 at 8:45 • @TheLethalCoder I do know about this. How do you think I can make it tidier without removing content? – V. Courtois Jul 24 '17 at 8:46 • To be honest I have no clue, if I knew more on the subject I'd be able to help more – TheLethalCoder Jul 24 '17 at 8:49 • @TheLethalCoder mmh okay. Japanese mahjong is a well documented topic (I already linked some docs in the post). So maybe I shouldn't define the rules myself and let a link do the job? – V. Courtois Jul 24 '17 at 8:52 • Well you'd want the important information in the post so it is self contained. Maybe the "fluff" can be trimmed down. – TheLethalCoder Jul 24 '17 at 8:53 I'm sort of brainstorming a challenge. I'm not really paying attention to question format at the moment. The challenge would be to generate and populate a Golf Scorecard. The output would look something like this: Hole Par Strokes Score 1 3 3 0 2 5 4 -1 3 4 5 1 4 3 4 1 5 4 4 0 6 5 3 -2 7 4 3 -1 8 3 5 2 9 5 5 0 Totals 36 36 0  A Par value would be generated by choosing a random number in [3, 4, 5]. A Stroke value would be generated by choosing a random number within some range (say -2/+2 or -3/+3) of Par. A Stroke can be no lower than 1. Score = Stroke - Par Total is adding up all the values in that column (not including Hole). I'm wondering if it would be too much to ask to have the generated values be somewhat realistic (unlike my example output), in that Par values tend to be mostly 4, with about the same number between 3 and 5, and Stroke values tend to be close to or above Par, with it being very unlikely to be 1. # Proposed Question ## Triskaidekaphobic Primes It is known that a certain number, which lies between 12 and 14, brings bad luck. The Church of Triskaidekaphobia (CoTDP) asserts that the key to salvation is avoiding this number in all situations, such as numbering floors, license plates, space shuttle missions and more. The IT department of CoTDP is looking for talented developers. Candidates must prove their ability to program in accordance with Triskaidekaphobic dogma. Can you get this prestigious job? ## Your Mission Write a program that prints all prime numbers below 1000, excluding the unlucky one. the program must obey the CoTDP programming rules. ## Rules 1. Numbers whose absolute value is greater than 12 and smaller than 14 are considered unlucky and must be avoided. 2. Unlucky numbers must not be used in the program: • Must not appear in the program, in any representation/base. • Must not be the value of an expression or calculation (e.g. 5 + 8). • Must not be an intermediate value in an expression (e.g. 5 + 8 + 3, 35 % 22 == 0). • Must not be stored in a variable, register, memory etc (e.g. for i in xrange(20):). • Must not be passed to a function or returned from one. • The above applies to any complex type which contains an unlucky number (e.g. range(20) in Python 2). • The above applies to all expressions, not just constant expressions (e.g. x+1 is invalid if x happens to be 12). 3. No calculation, or intermediate value of a calculation, may yield an unlucky number. For example, and for i in xrange(20): are forbidden. 4. Output lines bust be separated by line-feed only (no carriage return). 5. You must find primes using basic mathematical operations. If your language provides tools to find primes or test primality, you must not use them. 6. Standard Loopholes apply. ## Scoring This is code-golf, the shortest solution (in bytes) wins. # Questions for Meta • Do the limitations make sense for all sorts of languages? I think they cover languages such as C/Python/Java that use expressions, and also languages such as BrainFuck that manipulate memory (I think it's obvious that you must not write 13 in a memory cell). • Is there a trivial solution that makes it uninteresting? • Would it be better as a popularity contest? • Or maybe, accept the shortest, but give a bounty for the most interesting/creative answer? • Can the expression "Church of Triskaidekaphobia" be considered offensive to followers of some churches? • Should we treat numbers such as 39 (13 * 3) as prime, or not prime for the sake of this calculation? If 13 is not a prime, then 39 is, but it's up to you. (I did something kind of similar to this here) – Stephen Jul 29 '17 at 19:15 • @StepHen, IMO, an unlucky divisor is still a divisor. I think asking for "primes below 1000, excluding the unlucky one" makes it clear. Your interpretation might make it more challenging, but I'm not sure how it would work - 39 is a multiple of 3 (though you shouldn't actually do this division), so how can it be prime? Maybe 169. – ugoren Jul 29 '17 at 19:23 • Related: we are not allowed to store 13, right? – Stephen Jul 29 '17 at 19:37 • @StepHen, I'm not sure what you mean by "store". My intention is that 13 won't be used in any way. I write that it can't be used in the program and can't be derived by calculation, so how can it be stored? – ugoren Jul 29 '17 at 20:12 • Well you could store it with x = ord("\r"), although if you can't use it there's not much point. – Stephen Jul 29 '17 at 20:25 • ord("\r") is an expression that yields 13, and is therefore invalid. But it's worth clarifying. – ugoren Jul 29 '17 at 20:27 • Your post (as it stands) says no calculation, not no expression. – Stephen Jul 29 '17 at 20:28 • Numbers whose absolute value is greater than 12 and smaller than 14 are considered unlucky and must be avoided. is 12.5 allowed? – l4m2 Apr 2 '18 at 19:09 # Fill to the line! Given input consisting of the characters _,  , and newline, fill the empty space up to the line! Example: I will use # as the filler character in the example. 1. Input ________ 2. Fill up to the line, but not above. ________ ######## ######## ########  • You may assume that the input either is rectangular (is padded), or consists only of the line and newlines. • You may assume that there is only one straight, unbroken line. • The whitespace above the line is part of the input. Do not fill above the line. Test cases: " Input " " Output " ********** " ---- " " ---- #### #### #### #### " ********** " ________ " " ________ ######## ######## ######## "  • is the input guaranteed to be rectangular? will the _ be on one line – Destructible Lemon May 24 '17 at 4:45 • @DestructibleLemon I will edit to clarify. – Comrade SparklePony May 24 '17 at 12:11 • If its padded its very trivial to just replace all the spaces with # – Notts90 supports Monica May 25 '17 at 8:30 • @Notts90 Not all the spaces, only the ones below the line. – Comrade SparklePony May 25 '17 at 12:08 • Ah ok, might want to make it clearer the bit above the line are included in the input. – Notts90 supports Monica May 25 '17 at 12:23 # Comparing Strings 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 , so shortest answer in bytes wins. • This is the canonical string equal question, but it does not allow you to use string comparison. – Stephen Aug 1 '17 at 21:37 • Bro... Come on, at least 3 sentences. – Magic Octopus Urn Aug 1 '17 at 21:39 • Do you need to handle strings with new lines or spaces in them? – geokavel Aug 2 '17 at 0:08 • @MagicOctopusUrn added a bit more clarification :P what else is there to say? – Stephen Aug 2 '17 at 1:21 • @geokavel clarified – Stephen Aug 2 '17 at 1:21 • This needs more information, test cases and to actually be made into a challenge. – TheLethalCoder Aug 2 '17 at 8:59 • @TheLethalCoder I forgot testcases - thank you. However, what else would I add to make it a challenge? – Stephen Aug 2 '17 at 11:03 • Usual boilerplate stuff, I'm sure something like this has been posted before too but I'm having trouble finding it. – TheLethalCoder Aug 2 '17 at 11:05 • @TheLethalCoder OK, how's that? and thanks for the feedback. – Stephen Aug 2 '17 at 11:15 • Better. I still don't like the challenge though it'll just lead to solutions like s=>t=>s==t?s:s+t Block ways of doing that and it'll be better – TheLethalCoder Aug 2 '17 at 11:18 • @TheLethalCoder hm, that was my idea for the harder challenge - that was why this says easy in the title. Do you think this is too trivial? I can just skip the easy one and go straight to the harder one. – Stephen Aug 2 '17 at 11:20 • I personally would. The easy one just leads to lots of FGITW answers. Yeah it'll probably be popular but boring. – TheLethalCoder Aug 2 '17 at 11:21 • @TheLethalCoder ok how's that? – Stephen Aug 2 '17 at 11:26 • Better but again I think you need to defend against the trivial cases i.e. ab, cd -> bc seems to be allowed and so does ab, cd -> bb yet they're both trivial changes to the inputs. – TheLethalCoder Aug 2 '17 at 11:30 • @TheLethalCoder I think I can only go so far in blocking those, and with what you have, for the your first case, entering aa, ab, and for your second case, entering aa, bc would result in invalid output. Half the fun here will be "cracking" them. – Stephen Aug 2 '17 at 11:37 # 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"  • So we're finding the seed to a pRNG that produces the correct output from a scrambled input? Have you actually managed to do this with any two none-trivial inputs? i.e. not just a few letters long? – TheLethalCoder Aug 3 '17 at 7:58 • @TheLethalCoder I was initially thinking of doing dicerolls instead of words, since those should be easier, but I liked words better because they fit the related question better. The sample code did work for 5 letter words. – JAD Aug 3 '17 at 8:22 # 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 , the answer with the highest score (upvotes minus downvotes) wins. • how to deal with the sun... – Destructible Lemon Aug 10 '17 at 4:30 • @HelkaHomba This URL is invalid or has expired. – Oliver Ni Aug 10 '17 at 5:50 • @DestructibleLemon Not sure, I'll think about it. – Oliver Ni Aug 10 '17 at 5:51 • What would i.stack.imgur.com/nkx4V.jpg become? – Calvin's Hobbies Aug 10 '17 at 6:39 • @HelkaHomba This is a popularity-contest, so that depends on how your algorithm handles it. The better it does, the more votes you will probably get.. – Oliver Ni Aug 10 '17 at 6:41 • Won't this fall under the usual "No objective winning criteria" that pop cons have been falling under lately? – TheLethalCoder Aug 10 '17 at 7:58 • @TheLethalCoder Fixed. – Oliver Ni Aug 10 '17 at 9:14 • @OliverNi How? The voting criteria is still subjective and that's why recent ones have been closed. – TheLethalCoder Aug 10 '17 at 9:17 • @TheLethalCoder as I know, "highest score (upvotes minus downvotes)" is exactly the defaults for popularity-contest, at least it is written in the tag description: "A popularity contest is a competition where the answer with the highest vote tally (upvotes minus downvotes) wins." – Oliver Ni Aug 10 '17 at 9:25 • @OliverNi Yeah you're winning criteria is fine. It's the subjective voting criteria I'm questioning. – TheLethalCoder Aug 10 '17 at 9:34 • @TheLethalCoder Voting is subjective. You can't just tell someone to 'downvote if the answer has x pixels that are y units apart from all the four neighboring pixels' or something like that. – Oliver Ni Aug 10 '17 at 9:37 • @OliverNi I know and isn't that the whole reason recent pop cons have been closed? Because the criteria people should vote on is subjective. – TheLethalCoder Aug 10 '17 at 9:39 • – Oliver Ni Aug 10 '17 at 9:39 • Provided you explicitly say what to do with the "dangerous" cases like the 'images with sun', this imo is a nice pop-contest but... you surely know well enough that pop-contests, almost always, don't garner much love here. – officialaimm Aug 10 '17 at 12:28 • So... if you vertically flip any of those images your algorithm would fail? – Magic Octopus Urn Aug 11 '17 at 20:38 ### Multiplicity of a Curve 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 • 1. My interpretation is that the multiplicity is just the minimum degree of all nonzero terms in the polynomial p(x-u, y-v). If this is true, stating so would simplify reading. 2. What input formats are permitted? Few languages have Polynomial as a type, so an input such as [[0,1],[2,3]] could be taken to represent 0x⁰y⁰ + 1x¹y⁰ + 2x⁰y¹ + 3x¹y¹. – fireflame241 Aug 20 '17 at 18:43 • I did not add the formats yet, but these are the two I had in mind, as we did it in previous challenges. – flawr Aug 20 '17 at 19:51 • Regarding the degree: Yes that is essentially what I wrote down, just a little bit more detailed for people who are not familiar with the topic. – flawr Aug 20 '17 at 21:39 # Hungry for Apples? This challenge is simple, given an integer 0 <= n or 0 < n, output an ASCII-apple with that many bites taken out of it. No bites (0):  // .-.:|.-. .' '' '. ; ; : : : : : : : ; '. : '-_.._-'  Bite 1:  // .-.:|.-. .' '' '. ; ; '-. : } : .-' : : ; '. : '-_.._-'  Bite 2:  // .-.:|.-. .' '' '. '-. ; } : } : } : .-' ; '. : '-_.._-'  Bite 3:  // .-.:|.-. .' '' '. '-. ; } .-' } { } '-. .-' ; '. : '-_.._-'  Bite 4:  // .-.:|.-. .' '' '. '-. .-' } { } { } { .-' '. '. : '-_.._-'  Bite 5:  // .-.:|.-. .' '' '. '-. .-' }". { } } { } } { .-'" '. '. : '-_.._-'  Bite 6:  // .-.:|.-. .' '' '. '-. .-' }"~". { } } } { } } } { .-'"~" '. '. : '-_.._-'  Bite 7:  // .-.:|.-. .' '' '. '-. .-' }"~"~".{ } } } }{ } } } }{ .-'"~"~" '. '. : '-_.._-'  Bite >7: [empty output]  # Rules • You may have trailing spaces, make it consistent though. • You may have exactly 1 trailing newline. • You are NOT doing an animation here, you are taking in n and outputting an apple. • You may error on integers less than 0, as the spec provides n > 0. • You must have empty output (no error) on n > 7/8. • You threw out the core; you didn't error the core into non-existence. • I feel this would be better if there was some more symmetry in the 5, 6, and 7 bytes so that people could possibly make better compression. – AdmBorkBork Aug 4 '17 at 18:26 • @AdmBorkBork better? – Magic Octopus Urn Aug 22 '17 at 21:26 • Yes, much better. – AdmBorkBork Aug 23 '17 at 12:33 # 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. • I'm not sure if the lookalike characters and penalty for non-ASCII characters is necessary. Drawing the beach, random placement and number of objects, and constrained placement of objects sounds like enough to me. The 80x25 hard constraint also seems superfluous. A line width limit of 80 keeps the idea, but would still allow for golfing in more verbose languages. – Andrew Aug 23 '17 at 18:53 # 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 , so may the shortest code win and the best programmer prosper... • This seems rather close to codegolf.stackexchange.com/q/91847/194 – Peter Taylor Aug 27 '17 at 15:51 • @PeterTaylor Dupe? – ckjbgames Aug 27 '17 at 22:06 • @PeterTaylor Also, how could I distinguish it and add something unique so that it isn't marked as a dupe? – ckjbgames Aug 27 '17 at 22:10 • My opinion in general is that when a question is a borderline dupe it's more productive to ditch it and try to think of a radically different question than to try to bisect to find the minimal sufficient difference. I don't see anything about this particular topic which would make it an exception to that general rule. – Peter Taylor Aug 28 '17 at 14:09 # 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? • Unclear? • Dupe? • @BusinessCat Ok, I think I'll restrict to TIO-only langs when I update the list. Thanks for the feedback! – programmer5000 Aug 23 '17 at 14:00 • 1. In the interests of clarity, when picking arbitrary numbers make them different. 44 seems to occur in two different contexts in the example. 2. The bit about adding to the list is unclear. Are you saying that after submitting an answer, you must edit the question? That will (a) cause conflicts; (b) (I think) cause the question to become community wiki quite quickly; (c) break the example. And to accomplish what? 3. Expanding on that previous question: what is the motivation? Even answer-chaining questions benefit from a clear motivation for the core task. – Peter Taylor Aug 23 '17 at 21:29 • @PeterTaylor I hope the recent edit clarified 2., and I will use a different list when I post this (1.) – programmer5000 Aug 24 '17 at 11:38 • @programmer5000 Röda – Erik the Outgolfer Aug 25 '17 at 14:15 • @programmer5000 Thanks, that clears up adding to the list. – AdmBorkBork Aug 25 '17 at 14:25 • You probably want to remove from the list either what language was previously printed or what language you're currently printing, that way the list remains modulo 100. – AdmBorkBork Aug 25 '17 at 14:28 • I think that every answer-chaining question so far has some mechanism to make it increasingly harder to extend the chain. With this one it seems to get easier to extend the chain rather than harder. Is this not a fundamental flaw? – Peter Taylor Aug 27 '17 at 17:34 • The way I read it, every answerer removes one item from the list and adds one item to the list, so it doesn't get shorter. – Peter Taylor Aug 28 '17 at 13:56 # 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? • This is a duplicate of this unfortunately – caird coinheringaahing Aug 29 '17 at 19:05 • @cairdcoinheringaahing Shoot, all that time searching for "Pride" and "Flags", forgot to search for rainbow! Perhaps this is significant-enough a variant (rectangle vs bow) that it will allow for different approaches though. I'm not sure what the etiquette is, but I guess I'll leave this up for a while longer and let votes tell me whether it is too much of a duplicate to post. – Greedo Aug 29 '17 at 19:25 • personally, I would close as a duplicate, but if you want to keep it here and see otherwise, go ahead. – caird coinheringaahing Aug 29 '17 at 19:26 # 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 rules apply. ## Meta Looking for suggestions of a better title. • Well, I'm not sure what "Using the area of your own source code" means. I could do some pretty "standard" approximation algorithm to fullfill your rules. – Felix Palmen Aug 29 '17 at 16:58 • Wouldn't print(3.14) work? It isn't hardcoding pi, as pi isn't 3.14. – caird coinheringaahing Aug 29 '17 at 19:22 • @FelixPalmen - I've updated the specification. Hopefully it is more clear. – CzarMatt Aug 29 '17 at 20:14 • @cairdcoinheringaahing - I've updated the specification. Hopefully it is more clear. – CzarMatt Aug 29 '17 at 20:16 # "Square Root of Pi(e)" 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! • You don't ever define How one forms the pie shape, and in general you seem to be lacking specification. – Wheat Wizard Sep 3 '17 at 3:37 # The Best Question 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. • Is that abs((QuestionScore/2)-Answers)/2 or abs(QuestionScore/(2-Answers))/2? – Shaggy Sep 1 '17 at 12:05 • Hopefully this looks a bit better. – geokavel Sep 1 '17 at 15:29 # Extend the Pattern 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...) • Is there freedom to choose which quadrant of the output image corresponds to the input image? – Peter Taylor Sep 3 '17 at 18:05 • You need to add some harder test-cases - at present you can just check for overlaps, tile "infinitely" then crop. – wizzwizz4 Sep 4 '17 at 16:25 • @PeterTaylor Good question, I think I will leave the direction arbitrary. – flawr Sep 4 '17 at 19:53 • @wizzwizz4 I think this method works in any case, or do you have an example in mind where this does not work? – flawr Sep 4 '17 at 19:54 • @flawr One where there's less than one copy of the parallelogram... wait, that wouldn't prevent the overlap technique from working. – wizzwizz4 Sep 4 '17 at 19:58 # 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,... • This encoding doesn't really work since no sensible architecture allows partial bits. Since each 3 bit word is already used, there is no way to distinguish say ,+. from ,+.. if you happen to fill the remaining bits in that way. That said, it isn't totally required for the question for this to work. Otherwise, the bonuses and scoring are needless and confusing, so I'd recommend removing them. – FryAmTheEggman Sep 3 '17 at 16:57 • Nearly every byte score on PPCG is decimal (base 10): I think you mean that fractional byte scores are possible. To deal with the padding problem, I suggest that you specify that where one or two padding bits are required, 0 should be used; and where three to seven are required, the padding should be 101 followed by as many 0s as necessary. Since [] must be balanced, this allows unambiguous detection of the padding on decompression. Then make sure to include a test case which ends in ] and requires no padding... – Peter Taylor Sep 4 '17 at 8:02 # 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? • If the only winning-criteria is "Percentage of the characters which can be changed without breaking it" then the answerer can arbitrarily pad their score with an irrelevant string if their language has very versatile quining capabilities. The other things "favored" only really count if it's a popularity-contest and challenges with that tag are discouraged. – Kamil Drakari Sep 7 '17 at 21:07 • Do you have any suggestions on how to score it? I can't think of any cross-language methods. – sdfgeoff Sep 7 '17 at 21:21 • Currently you are scoring it as (characters that can change / total), You could square or cube the total to incentivise golfing, that way padding can only hurt you. However you want to watch out for very short programs that make little effort to complete the task but by virtue of their shortness are highly scoring. – Wheat Wizard Sep 17 '17 at 0:35 # 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 : Reduce your byte-count to win. • Related – H.PWiz Sep 8 '17 at 17:41 • @H.PWiz, I'd call that a dupe; the count is the index. – Shaggy Sep 9 '17 at 11:48 • @Shaggy This one is restricted-complexity though – H.PWiz Sep 9 '17 at 12:00 • o(n) is impossible: this isn't a problem which can be solved without reading all of the input. If that were relaxed to O(n) I think this would fit the "Too broad" close criterion because a properly explained answer would be a (very good) doctoral thesis. The current state-of-the-art algorithms are O(2^(2n/3) + epsilon), so a polynomial algorithm would already be impressive, and a linear one would be astounding. – Peter Taylor Sep 11 '17 at 8:59 # 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 - the shortest answer in bytes wins! • Can I take 4 tuples (x,y) instead? – H.PWiz Sep 8 '17 at 17:46 • Of course. Are you golfing in Haskell? – racer290 Sep 8 '17 at 18:03 • I'm not golfing now. Many languages have tuples. – H.PWiz Sep 8 '17 at 18:05 • This is just a subset of this challenge. – AdmBorkBork Sep 8 '17 at 19:48 • Only up to a certain degree. The challenge you mentioned is ok with a truthy/falsey value. That makes a difference in chosing your "algorithm". – racer290 Sep 9 '17 at 5:17 ...? # 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? • It's not exactly a dupe of this one, but that one is the same spirit, and it's closed and locked, so I wouldn't expect this to be well received. Also see this and this – James Aug 22 '17 at 21:41 • @DJMcMayhem see edits – programmer5000 Aug 22 '17 at 22:05 # Where do I live? code-golfgeography* Given a coordinate pair, supporting at least 2 decimal places (precision .01), determine the country containing that coordinate pair. The coordinate will be on land and will be at least ~0.5 degrees (~50 km Great Circle distance; thanks Peter Taylor!) from any border or coastline. Input will be given as two decimal numbers in any reasonable format. Output should be the English name of the country according to this source; spaces, accents, non-alphanumeric characters, and capital letters are all optional. For countries like Iran, you can choose to output either "Iran" or "Islamic Republic of Iran". The same applies for all ...Republic... countries, like N/S Korea, Lao, Taiwan, etc. For Côte D'ivoire, you can choose to output either "Côte D'ivoire" or "Ivory Coast". Exact built-ins are not allowed (ahem Mathematica). Online APIs are not allowed (ahem Google Maps). Western and Southern coordinates can be given as a negative decimal or with W and S (you can also have N and E if wanted). Please specify your input format. You will have to handle coordinates in Antarctica. Apparently it's a country now. # Test Cases Input -> Output 43.26N, 79.54W -> Canada 37.42N, 94.88W -> United States of America 25.96N, 103.51W -> Mexico 9.39S, 59.39W -> Brazil 79.66S, 65.22E -> Antarctica 90.00S, 00.00E -> Antarctica # It's such a shame that 90N ?E/W is in the middle of the ocean 74.25N, 40.00W -> Greenland 63.08N, 15.34E -> Sweden 66.19N, 98.93E -> Russia 30.72N, 103.39E -> China 2.89S, 119.55E -> Indonesia 26.96S, 132.91E -> Australia  * not a real tag but I propose to add it • Does "at least 0.5 degrees from any border or coastline" mean "at least 55.6km from any border or coastline" (i.e. great circle distance)? – Peter Taylor Sep 11 '17 at 8:34 • @PeterTaylor Yes, thanks for the calculation. I'll just say ~50 km, thanks. – HyperNeutrino Sep 11 '17 at 12:12 [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

# [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

• Any tie breaking for regexes with the same score, e.g. length? – Laikoni Sep 11 '17 at 5:28
• 1. This is a meta-regex question, and scoring it just on test cases means that there are already programs out there which will generate a regex that gets a perfect score. As it stands it's a pretty pointless contest. 2. I don't see a specification for an HTML tag, or even a link to one. Why, for example, is < b implies b >` invalid? Without a spec it's even more a meta-regex question rather than an HTML question. 3. This isn't parsing HTML with regex. It's closer to lexing HTML with regex, and no-one said that that was impossible or would summon the Elder Ones. – Peter Taylor Sep 11 '17 at 7:50