# Sandbox for Proposed Challenges

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

Sandbox FAQ

## Posting

Write your challenge just as you would when actually posting it, though you can optionally add a title at the top. You may also add some notes about specific things you would like to clarify before posting it. Other users will help you improve your challenge by rating and discussing it.

When you think your challenge is ready for the public, go ahead and post it, and replace the post here with a link to the challenge and delete the sandbox post.

## Discussion

The purpose of the sandbox is to give and receive feedback on posts. If you want to, feel free to give feedback to any posts you see here. Important things to comment about can include:

• Parts of the challenge you found unclear
• Problems that could make the challenge uninteresting or unfit for the site

You don't need any qualifications to review sandbox posts. The target audience of most of these challenges is code golfers like you, so anything you find unclear will probably be unclear to others.

If you think one of your posts needs more feedback, but it's been ignored, you can ask for feedback in The Nineteenth Byte. It's not only allowed, but highly recommended!

It is recommended to leave your posts in the sandbox for at least several days, and until it receives upvotes and any feedback has been addressed.

## Other

Search the sandbox / Browse your pending proposals

The sandbox works best if you sort posts by active.

To add an inline tag to a proposal use shortcut link syntax with a prefix: [tag:king-of-the-hill]. To search for posts with a certain tag, include the name in quotes: "king-of-the-hill".

Get the Sandbox Viewer to view the sandbox more easily!

# It's a small world! code-golf

A challenge inspired by small world networks. It is said that in such a network, starting at any point, you are able to reach any other node of the network in a specific amount of hops.

Your task will be determining the smallest number of hops necessary to reach any other node (maximum short-path length, aka graph diameter) and the average number of hops for the same purpose.

### Input

Your program will recieve on its stdin some amount of lines, with space-separated numbers on it.

Line number N will list the line numbers of the nodes node N is connected to. Every node is linked mutually, there are no unidirectional eges.

2 3
1 4
1
2


Each line can be assumed to be sorted.

### Output

Your program must compute the smallest number of hops necessary to depart from one node and land on any different node, and the average number of hops to traverse any node. Print it to stdout in any format desired. The average path length must be a decimal with at least 2 digits of precision.

The average path length is defined (for the purposes of this challenge) as the sum of the smallest number of hops between any 2 points divided by the amount of edges in the network (direct connections) plus the biggest short-path. The sum-of-short-paths includes the edges themselves (e.g. paths to neighbouring nodes), but not reversed paths (A to B and B to A).

sum(short_paths)/(edges+long)


### Example

The network represented in this image:

Will be input to your program as:

2 4
1 3 5
2 4
1 3
2


And the program must output something in the form of:

3
2.0


The average was calculated in this manner:

p12 = 1; p13 = 2; p14 = 1; p15 = 2; p23 = 1; p24 = 2; p25 = 1; p34 = 1; p35 = 2; p45=3
e = 5
A = sum(p) / (e+p45)
(5+8+3)/(5+3)


### Rules

Basic rules, avoid standard loopholes

I can see an issue with the "average" part of the challenge, since it is ill-defined and I consider this challenge quite extensive without it already.

• It took me awhile to understand your notation for the graphs. Maybe something along the lines of “line no. n lists the nodes node n is connected to” would be clearer. Sep 23 '15 at 6:28
• I'm also unsure if the calculation of the average should be part of the challenge, mainly because I defined it arbitrarily, and because the challenge should already be long enough without it. Sep 23 '15 at 12:40
• The average path length is well defined provided that you specify that the graphs will be connected. The other parameter is more of a problem: you call it "maximum path length", but that sounds like the longest path, and what you seem to be describing is the graph diameter. We've had a couple of longest path questions already; we haven't had graph diameter or average path length, although arguably they're trivial variations on all-sources shortest path. I'm not sure offhand whether that's been done, or just single-source. Sep 23 '15 at 13:36

# Find Your Stack Exchange Spirit Pokemon code-golf

It's a popular game on the internet to take some numbers related to someone (usually their birthday/age), multiply them, and divide until you get a number between 1 and 720. That number is the Pokedex number of your "spirit Pokemon".

We're going to play the same game, but since this is Stack Exchange, we'll be using our user IDs. And since this is PPCG, we'll be writing a program to tell us what our Stack Exchange-based spirit Pokemon is.

To find it, take any user, then multiply their user ID by the number of letters in their name. Take that number mod 720, then add 1 (so 0 will become 1 and 719 will become 720). That's the Pokedex number of their spirit Pokemon.

Input

A valid user ID greater than 0, and a valid name, in this format:
<ID> <name>

The site does not matter, and it won't be given.

You may accept input from either the command-line or STDIN (or your language's closest equivalent.)

Output

The name of the user's spirit Pokemon (as determined above.)

Since there's no way you can cram 720 names into one program, you'll be given a file with the names of all the Pokemon (in order). Here it is:

Bulbasaur
Ivysaur
Venusaur
Charmander
Charmeleon
Charizard
Squirtle
Wartortle
Blastoise
Caterpie
Metapod
Butterfree
Weedle
Kakuna
Beedrill
Pidgey
Pidgeotto
Pidgeot
Rattata
Raticate
Spearow
Fearow
Ekans
Arbok
Pikachu
Raichu
Sandshrew
Sandslash
Nidoran♀
Nidorina
Nidoqueen
Nidoran♂
Nidorino
Nidoking
Clefairy
Clefable
Vulpix
Ninetales
Jigglypuff
Wigglytuff
Zubat
Golbat
Oddish
Gloom
Vileplume
Paras
Parasect
Venonat
Venomoth
Diglett
Dugtrio
Meowth
Persian
Psyduck
Golduck
Mankey
Primeape
Growlithe
Arcanine
Poliwag
Poliwhirl
Poliwrath
Abra
Alakazam
Machop
Machoke
Machamp
Bellsprout
Weepinbell
Victreebel
Tentacool
Tentacruel
Geodude
Graveler
Golem
Ponyta
Rapidash
Slowpoke
Slowbro
Magnemite
Magneton
Farfetch'd
Doduo
Dodrio
Seel
Dewgong
Grimer
Muk
Shellder
Cloyster
Gastly
Haunter
Gengar
Onix
Drowzee
Hypno
Krabby
Kingler
Voltorb
Electrode
Exeggcute
Exeggutor
Cubone
Marowak
Hitmonlee
Hitmonchan
Lickitung
Koffing
Weezing
Rhyhorn
Rhydon
Chansey
Tangela
Horsea
Goldeen
Seaking
Staryu
Starmie
Mr. Mime
Scyther
Jynx
Electabuzz
Magmar
Pinsir
Tauros
Magikarp
Lapras
Ditto
Eevee
Vaporeon
Jolteon
Flareon
Porygon
Omanyte
Omastar
Kabuto
Kabutops
Aerodactyl
Snorlax
Articuno
Zapdos
Moltres
Dratini
Dragonair
Dragonite
Mewtwo
Mew
Chikorita
Bayleef
Meganium
Cyndaquil
Quilava
Typhlosion
Totodile
Croconaw
Feraligatr
Sentret
Furret
Hoothoot
Noctowl
Ledyba
Ledian
Spinarak
Crobat
Chinchou
Lanturn
Pichu
Cleffa
Igglybuff
Togepi
Togetic
Natu
Xatu
Mareep
Flaaffy
Ampharos
Bellossom
Marill
Azumarill
Sudowoodo
Politoed
Hoppip
Skiploom
Jumpluff
Aipom
Sunkern
Sunflora
Yanma
Wooper
Quagsire
Espeon
Umbreon
Murkrow
Slowking
Misdreavus
Unown
Wobbuffet
Girafarig
Pineco
Forretress
Dunsparce
Gligar
Steelix
Snubbull
Granbull
Qwilfish
Scizor
Shuckle
Heracross
Sneasel
Teddiursa
Ursaring
Slugma
Magcargo
Swinub
Piloswine
Corsola
Remoraid
Octillery
Delibird
Mantine
Skarmory
Houndour
Houndoom
Kingdra
Phanpy
Donphan
Porygon2
Stantler
Smeargle
Tyrogue
Hitmontop
Smoochum
Elekid
Magby
Miltank
Blissey
Raikou
Entei
Suicune
Larvitar
Pupitar
Tyranitar
Lugia
Ho-oh
Celebi
Treecko
Grovyle
Sceptile
Torchic
Combusken
Blaziken
Mudkip
Marshtomp
Swampert
Poochyena
Mightyena
Zigzagoon
Linoone
Wurmple
Silcoon
Beautifly
Cascoon
Dustox
Lombre
Ludicolo
Seedot
Nuzleaf
Shiftry
Taillow
Swellow
Wingull
Pelipper
Ralts
Kirlia
Gardevoir
Surskit
Masquerain
Shroomish
Breloom
Slakoth
Vigoroth
Slaking
Shedinja
Whismur
Loudred
Exploud
Makuhita
Hariyama
Azurill
Nosepass
Skitty
Delcatty
Sableye
Mawile
Aron
Lairon
Aggron
Meditite
Medicham
Electrike
Manectric
Plusle
Minun
Volbeat
Illumise
Roselia
Gulpin
Swalot
Carvanha
Sharpedo
Wailmer
Wailord
Numel
Camerupt
Torkoal
Spoink
Grumpig
Spinda
Trapinch
Vibrava
Flygon
Cacnea
Cacturne
Swablu
Altaria
Zangoose
Seviper
Lunatone
Solrock
Barboach
Whiscash
Corphish
Crawdaunt
Baltoy
Claydol
Lileep
Anorith
Armaldo
Feebas
Milotic
Castform
Kecleon
Shuppet
Banette
Duskull
Dusclops
Tropius
Chimecho
Absol
Wynaut
Snorunt
Glalie
Spheal
Sealeo
Walrein
Clamperl
Huntail
Gorebyss
Relicanth
Luvdisc
Bagon
Shelgon
Salamence
Beldum
Metang
Metagross
Regirock
Regice
Registeel
Latias
Latios
Kyogre
Groudon
Rayquaza
Jirachi
Deoxys
Turtwig
Grotle
Torterra
Chimchar
Monferno
Infernape
Piplup
Prinplup
Empoleon
Starly
Staravia
Staraptor
Bidoof
Bibarel
Kricketot
Kricketune
Shinx
Luxio
Luxray
Budew
Cranidos
Rampardos
Shieldon
Bastiodon
Burmy
Mothim
Combee
Vespiquen
Pachirisu
Buizel
Floatzel
Cherubi
Cherrim
Shellos
Gastrodon
Ambipom
Drifloon
Drifblim
Buneary
Lopunny
Mismagius
Honchkrow
Glameow
Purugly
Chingling
Stunky
Skuntank
Bronzor
Bronzong
Bonsly
Mime Jr.
Happiny
Chatot
Spiritomb
Gible
Gabite
Garchomp
Munchlax
Riolu
Lucario
Hippopotas
Hippowdon
Skorupi
Drapion
Croagunk
Toxicroak
Carnivine
Finneon
Lumineon
Mantyke
Snover
Abomasnow
Weavile
Magnezone
Lickilicky
Rhyperior
Tangrowth
Electivire
Magmortar
Togekiss
Yanmega
Leafeon
Glaceon
Gliscor
Mamoswine
Porygon-Z
Probopass
Dusknoir
Froslass
Rotom
Uxie
Mesprit
Azelf
Dialga
Palkia
Heatran
Regigigas
Giratina
Cresselia
Phione
Manaphy
Darkrai
Shaymin
Arceus
Victini
Snivy
Servine
Serperior
Tepig
Pignite
Emboar
Oshawott
Dewott
Samurott
Patrat
Watchog
Lillipup
Herdier
Stoutland
Purrloin
Liepard
Pansage
Simisage
Pansear
Simisear
Panpour
Simipour
Munna
Musharna
Pidove
Tranquill
Unfezant
Blitzle
Zebstrika
Roggenrola
Boldore
Gigalith
Woobat
Swoobat
Drilbur
Audino
Timburr
Gurdurr
Conkeldurr
Tympole
Throh
Sawk
Leavanny
Venipede
Whirlipede
Scolipede
Cottonee
Whimsicott
Petilil
Lilligant
Basculin
Sandile
Krokorok
Krookodile
Darumaka
Darmanitan
Maractus
Dwebble
Crustle
Scraggy
Scrafty
Sigilyph
Cofagrigus
Tirtouga
Carracosta
Archen
Archeops
Trubbish
Garbodor
Zorua
Zoroark
Minccino
Cinccino
Gothita
Gothorita
Gothitelle
Solosis
Duosion
Reuniclus
Ducklett
Swanna
Vanillite
Vanillish
Vanilluxe
Deerling
Sawsbuck
Emolga
Karrablast
Escavalier
Foongus
Amoonguss
Frillish
Jellicent
Alomomola
Joltik
Galvantula
Ferroseed
Ferrothorn
Klang
Tynamo
Eelektrik
Eelektross
Elgyem
Beheeyem
Litwick
Lampent
Chandelure
Axew
Fraxure
Haxorus
Cubchoo
Beartic
Cryogonal
Shelmet
Accelgor
Stunfisk
Mienfoo
Mienshao
Druddigon
Golett
Golurk
Pawniard
Bisharp
Bouffalant
Rufflet
Braviary
Vullaby
Mandibuzz
Heatmor
Durant
Deino
Zweilous
Hydreigon
Larvesta
Volcarona
Cobalion
Terrakion
Virizion
Thundurus
Reshiram
Zekrom
Landorus
Kyurem
Keldeo
Meloetta
Genesect
Chespin
Chesnaught
Fennekin
Braixen
Delphox
Froakie
Greninja
Bunnelby
Diggersby
Fletchling
Fletchinder
Talonflame
Scatterbug
Spewpa
Vivillon
Litleo
Pyroar
Flabebe
Floette
Florges
Skiddo
Gogoat
Pancham
Pangoro
Furfrou
Espurr
Meowstic
Honedge
Aegislash
Spritzee
Aromatisse
Swirlix
Slurpuff
Inkay
Malamar
Binacle
Barbaracle
Skrelp
Dragalge
Clauncher
Clawitzer
Helioptile
Heliolisk
Tyrunt
Tyrantrum
Amaura
Aurorus
Sylveon
Hawlucha
Dedenne
Carbink
Goomy
Sliggoo
Goodra
Klefki
Phantump
Trevenant
Pumpkaboo
Gourgeist
Bergmite
Avalugg
Noibat
Noivern
Xerneas
Yveltal
Zygarde
Diancie
Hoopa


Rules

• The file containing all the Pokemon must be saved as "pokemonlist".
• You may not open any files other than "pokemonlist".
• The program must output the name of the Pokemon, not just the number.
• Your program must work for any valid Stack Exhange user name and ID.

Bonuses

• -50 points if you return "MissingNo." if the input -1 Community is entered.

Meta Questions

• Are the rules clear?
• Is the formula enough of a challenge?
• I had a problem with the previous formula being too easy, so I've changed it. However, I'm not sure whether the problem was in the formula or the challenge itself. Will this challenge work, or is it too easy regardless of what formula I use?
• I sincerely object to any formula where I end up a Palpitoad. Sep 22 '15 at 18:50
• On-topic: This is really just "print line X%720+1 from this file", right? Sep 22 '15 at 18:52
• @Geobits Yes. I'll probably have to rework the formula so it's not that simple. Sep 22 '15 at 18:58

# Prove Your Language's Turing Completeness code-golf

The goal is to show whether your language is or isn't Turing complete with the shortest program possible. This is different than "interpret BF" questions, since that's only one way to show the completeness of a language.

This question will maintain one for each programming language (using a snippet), so the goal is to have either the shortest Turing machine, or the shortest proof that your language isn't Turing complete.

Good luck with Malboge.

This is probably a weak question so far, and so it needs your suggestions!

• Also, I'm not really sure how it'd work for non-Turing complete languages...
• Also, are there any languages whose Turing completeness is undecidable? Sep 24 '15 at 18:07
• What do you mean by "the shortest Turing machine"? Are you planning to write a spec for an input format which describes the TM (according to a specified commonly-used definition) and its starting tape? Sep 25 '15 at 11:07
• @PeterTaylor Not really. I could use some help with the wording. I really just want the user to show the Turing completeness of their language, which could involve implementing Rule 110, or interpreting BF, or several other things. Or are you saying a need a more specific definition of what it means to be Turing complete? Sep 25 '15 at 16:46
• I did actually start writing a comment asking what assumptions we could make about other systems being Turing complete, and then I saw that you talked specifically about having "the shortest Turing machine" and I rewrote the comment. If you generalise it then it becomes even more difficult: a proof that my language can implement all mu-recursive functions is really going to be a set of snippets showing how to handle each case, not a program. I think the approach which would cause least arguments would be to ask for implementations of a specific universal TM, and forget the non-TC langs. Sep 25 '15 at 21:35
• @PeterTaylor Do you know of any good ones that haven't been done? Conway's Game of Life, Rule 110, Cyclic Tag System, Lambda Calculus, and BF have all been done. I was really hoping for a generic, "implement a TC" code-golf... Sep 25 '15 at 21:53
• I see the confusion: you're using "Turing machine" to mean "Turing-powerful system", whereas I was interpreting it to mean machines made of a tape and a finite state machine. sciencedirect.com/science/article/pii/S0304397596000771 includes the UTM which was used to prove that Magic: the Gathering is TC (2 states, 18 symbols): it seems as good as any for your purpose. Sep 26 '15 at 6:10

# Hello, Loophole Abuse!

## Assignment

Print the following string:

Hello, World!


## Gimmick

you know the meta post "Loopholes that are forbidden by default"? Yeah, those don't apply here. In fact, you're actively encouraged to use as many as possible and combine them in weird ways. the more you use in a way that other users like, the more chance people will vote for you.

In addition, to prevent trivial answers getting all the glory, your program must also work in the event that the characters that make up the source code are reversed (this includes the separate characters of a string). This includes external sources, multi-character compiler and execution flags, file names and anything else that is essential for the execution of the software (like Metagolfscript IDs).

## Scoring

This is .

• Sep 26 '15 at 21:13
• @PeterTaylor If we can figure out a way to make the subjective part, i.e. determining which loopholes are broken, more objective, would that fix the question? Sep 26 '15 at 21:34
• Relevant chat discussion: chat.stackexchange.com/transcript/message/24349167#24349167 Sep 26 '15 at 21:47
• To be perfectly honest, I think it's such a pointless idea that I don't want to spend much time thinking about hypothetical changes. Sep 27 '15 at 6:14
• Characters reversed means reading the program from last to first character? Oct 11 '15 at 8:27
• @PaŭloEbermann Yes. So that means that, for example, closing brackets will come before opening brackets, Oct 11 '15 at 10:02

# PPCG New Question Generator

### Specification

Write a program that does the following, given a string s and an integer n (as a file, STDIN, or command line arguments):

1. Determines the n most used characters in that quote. If there are two characters that are equally used, the character with the lower ASCII value takes priority.
2. Returns the text and the character in the following format:

Return the following text:

>{string}

But there's an ORIGINAL TWIST! You cannot use the characters {characters} in your answer. As this is code-golf, the answer with the least characters wins. Have fun!


Specifics:

1. You need to display {string} in blockquotes using Markdown formatting, not HTML. So if the string spans multiple lines, you need to prepend each line with >.
2. You also need to display {characters} using proper grammar and in order from most used to least used. For example, with "a", "b", and "c":

You cannot use the characters "a", "b", or "c" in your answer.

### Example

In this example, n is 4, and s is:

I have loved flowers that fade,
Within whose magic tents
With sweet unmemoried scents:
A honeymoon delight,
A joy of love at sight,
That ages in an hour
My song be like a flower!


The output is:

Return the following text:

>I have loved flowers that fade,
>Within whose magic tents
>With sweet unmemoried scents:
>A honeymoon delight,
>A joy of love at sight,
>That ages in an hour
>My song be like a flower!

But there's an ORIGINAL TWIST! You cannot use the characters "e", "a", "h", or "o" in your answer. As this is code-golf, the answer with the least characters wins. Have fun!


# Remove Pieces from Chess Position Notation

You should write a program or function which receives a string representing a chess position as input and outputs or returns the position with only the pawns and kings left.

The positions in the input and output are described by FEN notation:

Each rank is described, starting with rank 8 and ending with rank 1; within each rank, the contents of each square are described from file "a" through file "h". Each piece is identified by a single letter taken from the standard English names (pawn = "P", knight = "N", bishop = "B", rook = "R", queen = "Q" and king = "K").[1] White pieces are designated using upper-case letters ("PNBRQK") while black pieces use lowercase ("pnbrqk"). Empty squares are noted using digits 1 through 8 (the number of empty squares), and "/" separates ranks. (taken from Wikipedia)

For example

rnbqkbnr/pp1ppppp/8/2p5/4P3/2N5/PPPP1PPP/R1BQKBNR


describes the board

---------------
♜♞♝♛♚♝♞♜
♟♟  ♟♟♟♟♟

♟
♙
♘
♙♙♙♙  ♙♙♙
♖  ♗♕♔♗♘♖
---------------


With everything except kings and pawns removed it becomes

---------------
♚
♟♟  ♟♟♟♟♟

♟
♙

♙♙♙♙ ♙♙♙
♔
---------------


and expressed with the FEN string

4k3/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/4K3


## Input

• A FEN string consisting of the characters 12345678PNBRQKpnbrqk/.
• The input describes a valid chess game position.

## Output

• A FEN string describing the position with knights, bishops, rooks, queens removed.
• Output might not be a valid chess position in some extreme cases.

## Examples

TODO


This is code golf so the shortest entry wins.

# Pareto optimality challenge

Write a class that maintains a pareto optimal set. This class must have these three methods:

k(int n): Constructs the class. N is the array size that all of the other methods must use.

boolean k.p(int[] n): Adds n if there exists no entry m in k such that each single term of m is greater than each corresponding term in n. The method must also return true if n has been entered into k, or false otherwise. n can be assumed to be of the length specified by the constructor.

boolean k.s(int[] n): Returns true if n was previously entered by the above method and there exists no other term m in k such that each term of m is greater than each corresponding entry in n. Returns false otherwise.

This is code golf, so shortest entry wins. Yes, programming languages without classes may be used, but all the usual properties of classes must be satisfied by the three methods above.

# ASCII Snake

NOTES

It was pointed out to me that we already have had at least 2 snake challenges before. However, seeing as they are from a couple years ago, I think another snake challenge would be nice. Below (from the description section to the end) I describe a "classic" snake challenge.

However, I want to differentiate this from the classic challenge. I am more than open to suggestions in the comments below. My idea is the following:

Make an "infinite" snake game. That is, every 10 points, the level changes and the snake is reset according to the following pattern:

--The nth level contains n obstacles in the form of the '#' character. These work the same as walls. They are randomly placed around the map, the difficulty is that they cannot create a situation where an ungettable 'x' exists. for example:

------------------------------
| #                          |  11
|                            |
|              oooooo        |
|              o    o        |
|              o    v        |
|              o             |
|                            |
|                            |
|    x                       |
|                            |
------------------------------


would be unacceptable because if an "x" were to spawn in the corner, it would be an automatic game over. Also, the barriers may not form a wall which closes off areas of the arena.

I can flesh out this idea more if you think it is any good.

# Please Give Me Feedback On This Question

When I have a working question, I will begin work on a basic solution in C++.

Description

The goal of this challenge is to create a real time (non-buffered input) ASCII version of the popular game Snake .

The board is 10 newlines by 32 spaces. The boundary consists of the " | " and " - " characters.

The snake body is made of the "o" character.

The snake head is v,<,>,^ depending on direction of travel (intuitively)

The snake eats " x ".

For example a game board might look like:

------------------------------
|                            |  11
|                            |
|              oooooo        |
|              o    o        |
|              o    v        |
|              o             |
|                            |
|                            |
|    x                       |
|                            |
------------------------------


In the new game, the snake has three body segments and a head. It gains one body segment every time it eats an "x".

The score (the number of segments+head) should be displayed somewhere on the screen.

The starting position of the snake and the starting position of the "x" is left to the writer.

After an "x" is eaten, the snake gains a segment, and a new "x" must spawn. "x"s may not spawn in a set of predetermined coordinates. They must spawn "pseudo-randomly" in the loosest sense of the phrase. This means that they can spawn using a random number generator or their position may be simply a function of the snake's position or some such simple rule.

The snake moves according to nonbuffered user input according to one or both of the following layouts:

"W" - change direction up.

"A" - change direction left.

"D" - change direction right.

"S" - change direction down.

AND/OR

"UP" - change direction up.

"DOWN" - change direction left.

"LEFT" - change direction right.

"RIGHT" - change direction down.

Note that, as per the rules of snake, at a given instance of the game, only three options are available to the player:

-- Do nothing (and continue moving straight)

-- Turn 90 degrees

-- Turn -90 degrees

Therefore, at a given instance, two of the movement buttons should be unresponsive. E.g. in the above case, only right and left are responsive.

Snake movement follows the normal pattern. For those of you not familiar with it: Let segment zero, $$s_0$$ be the head and segment $$s_n$$ be the very end of the snake. In a given frame, the snake has 3 choices, go straight, go left, or go right (from the snake's reference frame). $$s_0$$ moves into one of these spaces based on user input. Then $$s_i$$ moves into the space taken by $$s_{i-1}$$ on the previous frame.

If an "x" is eaten, then on the next frame the new segment $$s_{n+1}$$ is placed where $$s_n$$ was on the previous frame.

The game ends when the snake head collides with the snake body or a with a wall.

Rules

1) Only languages which are available for free may be used. Libraries may be used (for i/o, etc), however the actual snake program must be written by you. (if library overuse is an issue, it will be determined by up/down votes)

2) The game must be playable (i.e. the framerate must be acceptable on most machines, as determined by readers)

3) The winner is the program using the smallest number of bytes that fits the above description.

4) If an online compiler is available, it is recommended that you link it with your code so that others may play your game.

• FYI, we've had a couple snake-based challenges already (1 2). Oct 5 '15 at 16:07
• Thank you. I'll either delete this post or come up with a way to make it fundamentally different. Since those were three years ago hopefully I can come up with a refreshing twist
– Liam
Oct 5 '15 at 19:06

# Machine Learning

If you give a downvote please say why! (otherwise how will I learn, thanks)

The task is to create a simple program that "learns"

-->The challenge is to create a program which:

(1) outputs 50 integers (1 at a time) and waits for input after each.

The input given will be 1 or 0 depending on whether the number is "good" or "bad" based on a predetermined pattern (see the pattern section for more information)

(2) The program will then output something to the effect of

<< Learning done. Ready for testing.


At which point it will wait for integer input.

(3) My script will then input 50 integers (1 at a time) and the program will read the integers and output 1 or 0 depending on whether it thinks the integer fits the pattern.

-->Types of Patterns

Patterns will be of the following types, in an unknown order

- is divisible by x (x no larger than 20)

- is greater/less than x (x no larger than 100)

- is a perfect square

- has exactly x prime divisors (x no larger than 3)

- is coprime to x (shares no common divisors with x except 1) (x no larger than 100 and not prime)

numbers above subject to change if a case is made in the comments

-->Scoring

Bots will be scored on correct answers to my script input. The score is equal to the total number of correct answers across all 5 tests. There is a max score of 250.

Since I do anticipate perfect scores, ties will be broken by golf score of the source.

Further ties will be broken by submission time.

-->Example of A Test

note: "in" is for my input. "out" is for machine output.

out<<  10
in>>   1
out<<  1901
in>>   0

... more lines like this ....

out<<  Learning Complete. Ready for Input.

in>>   12
out<<  1
in>>   87
out<<  0

... more lines like this ...


Say the machine got 47/50 correct on this test, then it currently has a score of 47. I would then proceed to test it with 4 different patterns. And sum its score on each test for its final score.

-->Rules

(1) you may not use external tables, i.e. have a library that contains table for all possible tests. However, your code may generate such tables.

(2) the bot may not exceed an average time of 2 seconds per output. This goes for both the learning and testing sections. I really don't want to have to spend over 15 minutes per test. The average is so that it can spend a bit of start-up time to generate tables if it needs to.

(3) Use of external libraries is permitted, although it should be clear that the bulk of the work is yours. (this will be determined by downvotes)

(4) Languages must have a free interpreter available. If they don't I won't be able to test them. This rules out MatLab, Mathematica, etc.

(5) other rules may be added as necessary.

• As interesting as this challenge sounds, I think you'd need a lot more than 5 test cases and 20 inputs to be able to see any sort of meaningful result. Oct 6 '15 at 4:44
• Really? Why do you say that? Regardless, that shouldn't be a problem, I could write a script to test the bots.
– Liam
Oct 6 '15 at 4:45
• Given only 5 * 20 = 100 inputs, I'd expect there to be only a difference of a few incorrect responses between the top answers, which is small enough to be caused by chance. Also, is there any limit on the size of the programs? Oct 6 '15 at 4:50
• Okay, I'll bump it up to 50 questions per test. I'll edit the scenario shortly. No, no size limit (should there be), although I think that I'll put in something to the effect of "bot must make decisions within 1 min at all steps"
– Liam
Oct 6 '15 at 4:52
• Mathematica is free. Oct 24 '15 at 23:47

Mutating variable

Output
n number of lines (where n is from 10 to 30, each run is random) where each line is either (all of the lines have to be possible)

1. Array of n random chars (or String with n random characters) made out of letters only
2. random int divisible by n (by int I mean a whole number of any kind)
3. random double whose first two decimal digits is n (by double I mean an number that has decimal digits) therefore for n=12 it will have format ###.12####
4. random boolean true or false (by that I mean 1 or 0)

No two consequent lines may be same type

Another requirement is that in your code may call print (or System.out.println or whatever you use to print to screen) only once.

This is code-golf, so shortest code wins.

By random I mean use your language's built-in random number generator,

• Why the strange "may only print once" requirement? Also, for random, it might be better to use a somewhat standard definition instead of "anything you like". That's just begging for the ubiquitous xkcd/Dilbert joke of constantly using the same output. Oct 7 '15 at 17:11
• @Geobits I edited the question to accommodate for the random suggestion you proposed. And for only one line to print. I just thought it would make task a bit harder is all, and I tried it on a few languages I know, and it did make things just a tad bit more tricky. Oct 7 '15 at 18:38
• Just a few more comments/questions: 1) You seem to have removed the part about all lines having to be possible 2) Is there a minimum number of choices for the random string/int/double? Otherwise I could just random between n and 2n, say. Oct 7 '15 at 22:35
• @Sp3000 I added requirement where all the lines have to be possible. Also what do you mean by minimum number of choices? I didn't quiteget the question you asked. Oct 8 '15 at 13:08
• You don't specify a range for the randomness, so the easiest thing to do is probably random between two possible options for everything, e.g. between n/2n for the int, or 0.n/1.n for the double, and "aaaaaaaaa"/"bbbbbbbbb" for the string Oct 8 '15 at 13:14
• @Sp3000 I thought that wherever I use word random I amply that they must use their language's random method. So if I say n random chars, I mean that every char has to be generated using the random method. How would I clarify that? Oct 8 '15 at 14:55
• Well the problem is that this has nothing to do with a language's random method. I could use random.choice("ab") or random.choice("abcdefg") - both use the language's random, but there's more outcomes in one than the other Oct 8 '15 at 15:17
• @Sp3000 so let the person use any random they like I guess. See no problem with aaaaa then bbbb and etc. As long as other requirements are met. The fun I wanted to see is printing all of those values and see the smallest amount of code. Oct 8 '15 at 15:36
• If you're fine with that then that's okay then I guess. Was just checking Oct 8 '15 at 15:42
• @Sp3000 so the question is ripe enough to post on the main site? Oct 8 '15 at 16:23
• I think if you add the explanation for "consequent lines" back in it'd be fine. The writing could be a bit better, but at least it's not as ambiguous now. Also, if by 10-30 you mean that 10 and 30 are both possible, then it might be good to write that as "10 to 30 inclusive". Oct 9 '15 at 10:29
• @Sp3000 Thanks for all your advice. I highly appreciate it! But I am leaving code golf for a while. As of late I noticed that it has become too toxic for my liking. Thanks for your help however :) Oct 9 '15 at 12:57

# Ceylon golfer (whitespace + comment removal)

As some people might have noted, I'm answering here often using Ceylon. This is usually done first writing a "normal" program, then slimming it down using whichever tricks I find, and at the last step remove all superfluous white space (and possibly also comments)

I want to automatize the last step.

Ceylon is syntax-wise a C-like language, so this golfer might be useful also for other languages. The details might differ, though.

This is similar to Remove Whitespace from a Java Program, but not the same, as Ceylon strings are a bit more complicated.

Details

A Ceylon program is a Unicode character stream, which can be lexically analized into a series of tokens, possibly separated by whitespace. (Only ASCII white space is allowed: space, tab, form feed (FF), line feed (LF), carriage return (CR).)

That whitespace is sometimes necessary – when otherwise the two tokens would stick together and form one token, or when a comment would become longer than before (but comments are to removed, too). Other whitespace can be removed.

Lines are terminated by LF, CR or a sequence of CR LF.

We have two kinds of comments:

• Multiline comments start with /* and end with */.
• end-of-line comments start with // or #! and end with the line (i.e. at the next line terminator).

Everything which is not whitespace or a comment is part of a token.

Tokens are of these forms:

• Identifiers or keywords start with a (uppercase or lowercase) letter and then can contain letters, _ and digits. They can also start with \I or \i instead. (Examples are true, Integer, a, helloWorld, example1234, \Iexample1234.)
• Literals:

• numeric literals (decimal integer, hex integer, binary integer, formal floating point, shortcut floating point) have the form [0-9_]+[kMGTPmunpf]?|\$[01_]+|\#[0-9a-fA-F_]+|[0-9_]+\.[0-9_]+(e[+-]?[0-9]+|[kMGTPmunpf])? (where the _ is only allowed at certain places). (Maybe that can be simplified to [#$0-9][0-9a-fA-FkMGFPmunpf._]*, with the dot not being the last character. Not all such strings are valid numeric literals, but I guess you don't have to figure them all out. The details are in the specification linked above.)

• Character literals have the form ' + single character (except " or \) or escape sequence + ', where an escape sequence is either a \{ + a name or code of a character + }, or a \ followed by a single (non-{) character.

Examples: ' ', '←', 'a', '\'', '', '\{#0020}', '\{#212B}', '\n', '\{ALCHEMICAL SYMBOL FOR GOLD}', '"', '\"', '\\', '/'.

• String literals:

• A simple string literal is " + a sequence of single characters (except ", \ and  ) and escape sequences (see above) + "
• An interpolated string literal (or string template) looks like a simple string literal, but can also contain  + some non-string-code +  inside the string. (In this non-string-code the whitespace and comment removal can be applied.)
• A verbatim string literal is """ + a sequence of any characters, except """, + """. (There is no escape sequences or interpolation here.)

There is further complication with multi-line string literals, but I guess for this challenge we can assume that there are no multi-line string literals.

Examples for String literals: "", """""" (both the empty string), "Hello World!", "Escapes: \{#212B}, \{ALCHEMICAL SYMBOL FOR GOLD}", """non-interpreted Escapes: \{#212B}, \{ALCHEMICAL SYMBOL FOR GOLD}""", "some more escapes: \n, \r, \f, \t, \b, \\, \, \', \"", "punctuation: '  \" and more text", """punctuation: '  " and even single \.""",

• A lot of symbols are punctuation and operators:

 , ; ... { } ( ) [ ]  ? . ?. *. = => + - * / % ^ ** ++ -- .. : -> !
&& || ~ & | === == != < > <= >= <=> += -= /= *= %= |= &= ~= ||= &&=


The grammar is such that whitespace adjacent to one of those punctuation tokens is never relevant, so it can be removed.

Challenge

Write a program which receives as input a valid Ceylon program, and outputs the same program, with all comments and non-essential white space removed.

Whitespace is essential when without it two tokens would be one token – this applies specifically to keywords/identifiers and numeric literals. In those cases replace any string of whitespace with a single space.

(I guess there are some cases like 10else where an integer literal can be joined with a keyword, but for safety it is better to always have a space in there.)

Of course, whitespace inside a string is highly relevant, so it should not be touched.

If a removed comment was the only thing between two keywords/identifiers, make sure to put a space in there.

Open questions

• I guess I should add some example inputs and expected outputs.
• How to score this? Simply as Codegolf, assuming there will be correct answers? Or give some example programs and see which entry succeeds to make them smallest?
• I guess most Ceylon programs to be golfed will actually be ASCII only – do we allow ASCII-only solutions, while giving a bonus for proper Unicode handling (in comments, strings, identifiers)?
• Do we require full programs, or allow also functions which take+return strings (or character streams)?
• Did I simplify the grammar not enough, or too much?
• I can imagine some bonuses for finding the shortest representation of an integer of float literal .. not sure if that is worth the complication.
• Another possible bonus would be to find the shortest way of representing a string literal (replacing some Unicode escapes by the actual characters, choosing between " and """, etc.).
• Do we want to handle multiline strings correctly? Maybe as a bonus?
• Another possible bonus would be to remove strings literals which are not passed or assigned to anything (these are often used for documentation comments) – but I'm not sure how to define that without specifying the whole grammar.

(Those have leadings space in the following lines, up to the column where the literal started, which needs to be removed when lexing. If we change the alignment of the string literal, we need to adjust those spaces too. Here it can sometimes be useful actually not include a new-line before the string to minimize that indentation.)

# Steganographic Image Encoding

Write two programs, an encoder and decoder. Score is the sum of the source in bytes.

## Encoder Specs

Input:

• a lossless 24-bit color image file
• could be anything from BMP to PNG to PPM
• an arbitrary data file
• undefined behavior if one attempts to encode a too-large file in a too-small image.
• an integer value, n, from 1 to 8, indicating the number of bits to use per subpixel.

Output:

An encoded image with the arbitrary data stored in the n least significant bits of the pixel data. The data must be stored in the pixels, i.e. not in some hidden metadata. How the data is serialized into the 3-D image space (height, width, color channel) is undefined.

## Decoder Specs

Input:

• an image produced by the encoder
• the arbitrary file's length in bytes
• the same integer value the decoder took indicating the number of bits per subpixel.

Output:

• the identical arbitrary data file as was provided to the encoder

## Requests for Comment:

• Fix n to 1?
• Encode the length/LSB's used in the image so you don't need to specify them again. (e.g. fixed format for a couple pixels to define it?) Requirement/Bonus?
• Maybe have the arbitrary data file be another image of the same dimensions, a la the Wikipedia example (cat in a tree)? That could be kinda boring though; some very simple array operations could do it all. Or that could be clever. In that case, there's necessarily data loss of the hidden image.
• If n was one and this only required an encoder, it would be the same as this, but this requires a matching decoder. One way encoding challenges I find dull.
• I'd be fine with using image libraries to load/save the image

# Time Series Analysis

Time series analysis comprises methods for analyzing time series data in order to extract meaningful statistics and other characteristics of the data (from here).

## The challenge

Write a program or function that take a time series vector ts and output a the coefficient of determination of a simple linear regression model estimated by the ordinary least squares.

The coefficient of determination should be the squared correlation between the predicted values of the model and the real values of the input, in such way that any perfectly linear time series should have 1  as it's coefficient.

### Considerations

• ts is a vector of racional numbers of length $\dpi{80} \boldsymbol{n | 2 \leq n \leq 99}$.
• To make the model assume ts is time sucessive and use time as its regressor.
• You can assume that ts is already loaded.
• You can't use build-in modeling functions such as lm() or similars.
• The input should be in any reasonable format.

### Examples

# input
1,2,3,4,5,6
# output
0


#input
0.244,0.569,1.575,1.965,2.604,3.493,4.084,4.436,5.209,6.110,6.979,7.245,8.229,9.161,10.309
# output
0.971


Let the shortest code win!

• This could use either a link to a page that clearly explains the terms and method used, or preferably a better explanation within the post. Oct 14 '15 at 18:42
• Good idea, I will link it. Oct 14 '15 at 18:43
• The fact that this is time series doesn't change anything since it's just OLS estimation, which is not specific to time series. OLS requires two dimensions, so x is essentially position in the series and y is the value of the series? Oct 14 '15 at 18:43
• I thought about saying time series to add some context, but yeah, it is just that, not sure about the output though. Oct 14 '15 at 18:46
• What does lm() do? Oct 14 '15 at 18:53
• @flawr lm() is a function in R for fitting linear models. Oct 14 '15 at 19:33

Objective

Given a string in Markdown, determine how much of the string is in bold and italic.

Test Cases

**Bold** --> 0
*Italic* --> 0
**_BI_** --> 2
__*abcde*__ --> 5
This is in **bold and _this_ is in italic** --> 4
\**_BI_** --> 0
\\**_BI_** --> 2
This is not in ___ bold-italic ___ --> 0

• Related. Oct 18 '15 at 16:47

Given the source code of a function or method to delete the first node having value x if existed, from a non-cyclic singly linked list, in a specific programming language. Write a program or function (not necessarily in the same language) to decide what kind of implementation it is.

You don't have to check for all the cases. But the more intelligent your code is, the better.

The possible implementations need to be checked are:

### Pointer of pointers

(Spec and examples to be added.)

(Spec and examples to be added.)

### Moving the data

(Spec and examples to be added.)

(And maybe some others.)

Possible winning criteria:

• Just .
• Something like where a submission is valid if no shorter programs can do all the things documented in the answer.

## Would someone like to write a crontab puzzle?

I have just asked for a software that displays all times at which a cronjob runs. As I think more about it, this might be a nice golfing question.

Unfortunately I'm not too familiar with the crontab specification, especially when it comes to combining operators such as

*/15,34,49-52 * * * * /path/to/command


Is that suitable for code-golf at all? If someone or a group of people would define it as a puzzle, I'd be glad to see it.

Starting point:

The program

• takes a crontab line as input
• checks if it is valid or not
• if valid, from now on lists the next execution times
• limited to a user definable amount

E.g.

program -n 10 30 17 * * *


produces 10 lines of output (assuming today is 2015-10-22 18:00)

2015-10-23 17:30
2015-10-24 17:30
2015-10-25 17:30
2015-10-26 17:30
2015-10-27 17:30
2015-10-28 17:30
2015-10-29 17:30
2015-10-30 17:30
2015-10-31 17:30
2015-11-01 17:30


# Word Game KotH king-of-the-hill

First of all, I don't know what this game is called (or if it even has a name), but it's a modification of a game I've played a few times on road trips, especially with my family. I'll be thinking of a better name.

Any suggestions at all are very welcome.

## How It's Played

There are 51 bots playing per game. At the beginning of the game, they are given a collection of letters (which is not necessarily a word), for example "a" or "jet." The bots take turns in a predetermined order. When it is a bot's turn it is passed the current word(s) and has four2 options:

1. It can change a single letter to any other letter.
2. It can add a single letter to any position in the word.
3. It can swap any two letters in the word.
4. It can split the word at any point.

If you didn't infer already, these actions are allowed with the caveat that their result is a valid word or two valid words, if the bot chooses to split. The game ends when the combined lengths of all the words in play are 3 times the length of the longest word in the dictionary used (e.g. if "onomatopoeia" is the longest word, the max length would be 36 letters since it has 12) or when only one bot remains. The bots are scored on how many turns they last*, and the winner of the game is granted a bonus3.

*The turn they lose on is not counted, so if the bot were to lose on its first turn it would have lasted 0 turns.

A word is valid if it is both in the dictionary and hasn't been played before.

Bots should take a reasonable amount of time in making their plays (no more than a few seconds).

## Available Methods

isValid(word) returns a Boolean value (whether the word is valid or not).

getDictionary() returns the entire dictionary as a single string.

getPreviousPlays() returns the words previously played as an array (one word per element).

Once any of the following methods are called, the bot's turn is over:

change(index,letter) changes the letter at that index to the letter provided. This method cannot change a space to a letter (to prevent stalling).

insert(index,letter) inserts the provided letter at the provided index.

swap(index1,index2) swaps the letters at index1 and index2.

split(index) splits the word into two by inserting a space at the specified index. Both of these words have to be valid4

If any of the calls to these methods are invalid, the bot is disqualified for that game (treated as a loss).

# Author's notes

1. Basically a random number I determined; I don't know if it's too big or small.
2. Is four too few to make this challenge interesting?
3. This bonus is undetermined as of now, but I'd say 2 points tentatively. I'm also a bit unsure as to whether that is a good scoring method. Should it just be on victories or position in victory (i.e. first, second, third, etc. place)? I'm also worried that this might encourage users to submit bots that collaborate to last as many rounds as possible.
4. Would it be more interesting if this ignored validity? e.g. if you have candies dog as the two words, splitting candies into can and dies would be valid even if either of those words had been played before.

I haven't done a KotH submission before, so I'd love feedback as to how to improve this.

## Unimplemented Portions

### Controller

This is the big unimplemented portion: I want to get feedback on the idea as a whole before diving into programming out a controller.

### Scoring

I'm still unsure as to how the games should be scored.

• I don't understand how the game starts. If I'm passed a bunch of random letters, surely the majority of the time I can't make a word and I lose immediately? Oct 24 '15 at 8:58

# Create CHIQRSX9+ Analogue Program.

Your task is to create a program in same language, that when given a CHIQRSX9+ will print a that analogue. That analogue program will do similiar thing that CHIQRSX9+ program do. There's exception though. There's may be more than 1 instruction. Then it's meant to be executed

1. C => Read until empty line and print all entered lines, including empty line.
2. H => Print "Hello, world!"
3. I => Read input until a newline then return that analogue
4. Q => Print the analogue program source code. (Not the entered one)
5. R => Read input until a newline then print that string after doing ROT-13
6. S => Read comma separated number until newline and sort that.
7. X => For this, X have undefined behavior.
8. 9 => Print 99 Bottles of beer with correct pluralization.
9. + => Increment Accumulator.

Printing instruction(C, H, I, Q, R, S, and 9) begin in a new line. After everything is printed, accumulator count is written at new line. Final newline is optional.

## Example

If there's program X written in Haskell, then

X
CH
>main=interact$(++"\nHello, world!\n0").unlines.takeWhile(/="").lines  Which when compiled (Example as W) will do that W This is a line This is another line >This is a line >This is another line > >Hello, world! >0  Another example for Q X Q >main=putStr(s++[';','s','=']++show s);s="main=putStr(s++[';','s','=']++show s)"  Yet another example X H+ >main=printStr"Hello, world!\n1"  Here is for indication of output. DO NOT print it. ## Sandboxing Question How about scoring. I want to reward short produced program. However, shorness of producing program is also counted. I guess just 10A+5B+C. Where A is length of original source code, B is length of "QQQQ" analogue program. C is length of "CHIQRS9+". • Well, please tell me what's wrong in my question? Oct 24 '15 at 15:51 • 1. I think this is a source-source compiler, which might be a more recognisable title than "create analogue program". 2. The HQ9+ family has a very mixed reception here, so you should probably expect some downvotes. 3. Why does the scoring system include a weight for votes? Oct 25 '15 at 7:43 • 1. If it source-source compiler, Q will compiled to main=putstr"Q\n0" instead. Oct 25 '15 at 13:10 • 2. What's wrong about HQ9+ except that it can be used to cheat at golfing. Oct 25 '15 at 13:11 • 3. Just a tiny boost since "QQQQ" "CHIQRS9+" and original source code is already very big. Wait I'm writing it wrong. It must be subtraction. Else it will be penalty Oct 25 '15 at 13:12 • Is that vote annoying? Oct 26 '15 at 8:05 • Congrats on posting the 1600th answer in the Sandbox! Oct 27 '15 at 15:57 Goal The goal is to stitch several ordered lists of numbers into a single list that contains each of those lists as a contiguous sublist, with the numbers in the same order without gaps. The resulting list should be as short as possible. Input n ordered lists of numbers between -2^63 and 2^63-1 Ouput A minimum-length list so that each input list appears within that list with its elements in the same order without gaps Example Input: [1, 2, 3] [3, -38, 23424, 292] [0, 1, 2] [-38]  Output: [0, 1, 2, 3, -38, 23424, 292]  The output contains each of the input lists: [0, 1, 2, 3, -38, 23424, 292] [1, 2, 3] [3, -38, 23424, 292] [0, 1, 2] [-38]  • Many languages have built-ins both for flattening a list of lists and for removing duplicates, giving them a straightforward solution. I think that makes this too easy overall. The removing duplicates part is like this challenge, though it uses characters and requires preserving order. – xnor Oct 30 '15 at 21:26 • But it is not only about removing duplicates, but also about finding the perfect combination of lists, so you have to figure out in which order you want to put the input lists together. Also it might be necessary to have duplicates in the output to be able to have all input lists in there. Oct 31 '15 at 7:13 • Oh, my mistake, I didn't realize the lists had to appear as contiguous subsequences. Let me edit that to try to make it clearer. – xnor Oct 31 '15 at 7:18 • Out of curiosity, I found notes about this as an algorithmic problem, and it's NP-hard, so solutions are going to be exponential time. It would do good to include some test cases that a greedy algorithm would get wrong. – xnor Oct 31 '15 at 7:29 • Looks like we already have this challenge. – xnor Oct 31 '15 at 8:53 • Good catch. It's indeed the same problem. Thanks for pointing that out! Oct 31 '15 at 9:03 # Hello, World! Fitted in cases. Your task is to take a line of input and print Hello,world! multiple times fitted to length of input. The cases of that character is fitted to input in same position(except shifted from deletion). If the corresponding character is non-alphabeth, you must use default case(lowercase except for "h" that is uppercase). And for punctuations, if the corresponding character is not punctuation, it will deleted. And if the corresponding character is space, the the ouput is space but it doesn't skip the "Hello,world" writing. ## Example Hello, world! Hello, world!  About punctuation deletion and space insertion I have a dog. I name it Underdog. H ello w orld H ello wo Rldhellow  Explanation Ihaveadog.InameitUnderdog. Hello,worlD!hello,world!hellow Helloworld!hello,World!hellow HelloworldHello,wOrld!hellow HelloworldHellowoRld!hellow HelloworldHellowoRldhellow  Other examples .....&^&%&*%&(&)^$#()&#()&@#)*%)#1-
Hello,world!Hello,world!Hello,world

UPPERCASES
HELLOWORLD

lowercases
helloworld

Abdeg,fGhiJ.
Hello,wOrlD!


## Example Program

Here is ungolfed version of example program in Python. If there is error, correct me.

p=readline()
h="Hello, world"
i=0
k=""
for a in xrange(len(p)):
if p[a]==" ":
k=k+" "
continue
if isUpper(p[a]):
if isAlpha(h[i]):
k=k+upper(h[i])
i=i+1
continue
if isLower(p[a]):
if isAlpha(h[i]):
k=k+lower(h[i])
i=i+1
continue
k=k+h[i]
i=i+1


## Sandbox Question

This language is surely need to be fixed.

# How am I doing?

My boss is a flashy sort of fellow. He likes all things animated.

He's asked me to write a progress bar to show the completeness of our super-secret project.

Now with me being me, I'm getting you to write this for me and showing the best one to my boss.

• Output a progress bar to stdout.
• Whenever a newline is sent to stdin, increase the percentage on the percentage bar by 1%
• If not already enabled and if possible in your language, set the terminal mode to non-echoing (stdin doesn't automatically get shown, think like when your typing in your password for sudo)
• You may not assume the cursor is in a certain position, it must produce a progress bar relative to where you started the program (no absolute jumps)

To help you, you may use ANSI escape codes, ANSI colour codes and any UTF-32 unicode points.

The winner is the entry with the most upvotes.

### Sandbox Notes:

• Is this too broad? - I'm sticking to ANSI only but I'm not saying anything else about what it looks like.
• Anyone care to say why this is worth a downvote?
– Blue
Nov 2 '15 at 17:12
• Popularity contests tend to attract them (even the good ones). Nov 3 '15 at 19:47
• This doesn't seem very tightly defined. Generally, the broader a popularity contest is, the more I expect it to gather downvotes. Nov 3 '15 at 19:48
• Also, a simple requirement means most of the popularity of an answer will come from optional extras rather than meeting the spec. See the line between art and programming for other's thoughts on this. Nov 3 '15 at 19:50
• Thanks for the link, I think I'll just let this question die here (I'm not sure if I should delete it or not, I'm going with not deleting it unless someone else says otherwise)
– Blue
Nov 3 '15 at 19:57
• I usually delete my challenges once I know for certain I will not post them, but for ones I (or someone else) might be able to salvage in future I leave them around. Nov 3 '15 at 19:59
• I don't think this one is ready for main, but remember that here (as on main) a lone downvote doesn't really mean anything. It could be anyone for any reason - rational or otherwise. Nov 3 '15 at 20:00

# Kaprekar Transformation

Kaprekar Transformation is an transformation a number by following that instruction:

1. Take n-digit integer.
2. Sort it anscending and descending.
3. Subtract the largest number and smallest number.

Your program have to do this:

1. Take 1 number, x.

2. Output all possible cycle and fixnums for doing repeated x-digit Kaprekar Transformation on all possible input. Rotation is considered same. So it is invalid to print:

[00],[09,81,63,27,45],[81,63,27,45,09]

The output is a list consisting of list representing the cycle. You may using any style of list and even intermix it with restriction that it should not be ambigous. For example, comma separated item with item using comma separated item with enclosing bracket is OK, but not comma separated item with item using comma separated item without enclosing bracket.

Example:

8
>[00000000],[43208766,85317642,75308643,84308652,86308632,86326632,64326654],[63317664],[64308654,83208762,86526432],[97508421]


Or

>[00000000],[[43208766,85317642,75308643,84308652,86308632,86326632,64326654],[63317664],[64308654,83208762,86526432],[97508421]]

• I'm afraid this is a duplicate: codegolf.stackexchange.com/q/2762/8478 ... also, for future reference, requiring one specific list format is bound to put an arbitrary set of languages at a massive advantage (those which can just use their native string format), while all others may have to do some non-trivial string processing which distracts from the (interesting) core of the challenge. Nov 2 '15 at 12:56
• @MartinBüttner No, it is the generalization. You have to handle arbitrary digit this time. And you have to detect cycle and find all cycle given a digit. Btw, there is typo. 2 39 is different example. Nov 2 '15 at 13:04
• Task one seems to be identical. The fact that the other challenge only has to work with 4-digit numbers doesn't seem substantial. I'm pretty sure almost any answer there can be adapted to a variable number of digits in a couple of bytes. As for Task 2, I did overlook that. You could simply reduce the challenge to just task 2 (I'm not even sure why you'd combine two independent tasks into a single challenge?). Even task 2 can be solved by simply looping the solution to task 1 over all possible X-digit numbers, but there might be other ways to golf this one. Nov 2 '15 at 13:07
• @MartinBüttner Then, why it isn't duplicate of codegolf.stackexchange.com/questions/1255/hitting-495-kaprekar ? Nov 2 '15 at 13:14
• Because it has been overlooked, I suppose. Fixed. Nov 2 '15 at 13:15
• @MartinBüttner Maybe add time limit make this different enough. Nov 2 '15 at 13:15
• I don't know. Since you have to output the entire list anyway, there is not much you can optimise beyond actually applying the transform until you hit a cycle. If you limited the challenge to the second task, a time limit might make more sense, but then again the second task might be different enough not to be a duplicate in the first place. Nov 2 '15 at 13:17
• @MartinBüttner Then remove task 1 and it won't be duplicate? And add speed limit. Nov 2 '15 at 13:29
• I don't even think a time limit is necessary for part 2. Nov 2 '15 at 13:30
• @MartinBüttner Is Task 1 still have to deleted. And please, don't discuss in the Chat, because I can't access that. Better use my email: christianirwanhw@gmail.com Nov 2 '15 at 13:57
• As I said above, I don't see why you would want to squeeze both tasks into a single challenge in the first place. (How would you score answers? Sum of the two solutions?) And if you split them up, then the first answer is certainly a duplicate, but the second is fine (and if you didn't split them up, I don't see why you'd redo the same challenge as part of another challenge either). Nov 2 '15 at 13:59
• The cycle identification is borderline duplicate of codegolf.stackexchange.com/q/26578/194 Nov 2 '15 at 14:32

# Stupid leaks

Considering how immensely successful my last two challenges have been, I'll do a different style this time.

Drip, drip, drip, drip...

It's the year 3000. Due to clean air shortages, a system was created that turns water into air. However, that caused a water shortage (don't you love progress?). Therefore, a new (expensive!) system was created to convert the air back into water.

All that to say that water prices have skyrocketed.

And yet, here you are, stuck with a leaky faucet. Plumbers are expensive, but if you do it yourself, you have to order the parts online and wait for them to get here. You need a way to determine what is cheaper: calling a plumber and getting it fixed in a day, or buying the parts online but having water leak until they get here.

## The input

You need to take seven positive numbers as input:

• The price of water per gallon g.
• The number of drops leaking per hour d.
• The number of gallons wasted per drop z. This will always be a floating-point number less than 1.
• The price of calling a plumber to fix it p.
• The price of ordering the parts online o.
• The number of hours it takes for the plumber to fix the leak l.
• The number of hours it takes for the parts to get here s.

Only g, z, p, and o can be floats; all the rest will be counting numbers (integers greater than 0).

The gallons of water wasted per hour from the leak is d*z*g. For the sake of brevity, let's call that rate R. If R*l+p is less than R*s+o, then you should print/return DIY!. If greater than, print/return Call the plumber!. If equal, print/return Whatever....

## Precision

Floating-point precision through calculations is very...weird. Basically, your program can use whatever your language's default is. If you're using a language where the default floating-point type has infinite precision. If your language's default floating-point type can lose precision throughout calculations (like in Python, where .1+.1+.1+.1+.1+.1+.1+.1 != .8), then that works, too.

Short version: floating-point semantics and precision are however your language is by default.

## Scoring

Code-golf. Shortest wins. Standard loopholes banned.

• What is a "counting number"? Does it include 0? You also might want to specify at what precision the equality will be checked (presumably hundredths?), and how rounding should be handled for the "Whatever..." case. Nov 2 '15 at 18:24
• @FryAmTheEggman Is this better? Nov 2 '15 at 21:03
• My language doesn't support floating point at all, so can I always just output Whatever...? More seriously, I'm failing to see the point of this question. Do some trivial arithmetic and then output one of three strings which between them take up 90% of the code? Nov 2 '15 at 21:15
• I think it is better, but I think you do have to spend a bit addressing Peter's comment about languages that don't support floats. Nov 2 '15 at 23:55

# Show How a Regex Is Matched

What your program or function should do:

1. Accept input of two strings; let's call them r and s.
2. Determine whether r is a valid regular expression (you can use any common definition of regex for this purpose, or any common definition of regexes but with lookahead and lookbehind removed; indicate which you're using). Otherwise, don't output.
3. If so, determine whether s matches r as a regex. Otherwise, don't output.
4. If so, output/print, in order, the part of r matched by each character of s, and also the part of s that matches it.

Note: You may use your language's regex-matching library for this.

Example:

Using PCRE; my inputs and outputs are r first and then s.

^.el*(o.*)*d\b and Hello, world!
^.ello......d\b and Hello, world

.\1\W and 800-555-1212
..\W and 00-

\b and a
\b and empty string

\d and a
no output (it doesn't match)

First floated in chat.
Not a dupe of Compile Regexes (which asks you to match regexes whereas this allows you to use the resources of your language to do so).

• 1. It sure looks like a dupe to me: what's your argument for it not being a trivial transformation of the previous question? 2. In your examples, you seem to try to draw a distinction between outputting the empty string and not outputting anything. How does that work? 3. What exactly is the output format? E.g. the first example and the second example don't seem to be consistent in their treatment of metacharacters. Nov 5 '15 at 22:49
• @PeterTaylor 1. It's not a dupe at all: the older question asks you to match regexes whereas this allows you to use the resources of your language to do so; also, the older question outputs a means of determining matching, without regard to how it's matched, whereas this requires an output of the latter. 2. This question is OBE because of the edit I'm doing to fix #3. 3. Yeah, I messed up an example: I'll fix that immediately. Nov 5 '15 at 23:05
• 1. With respect to the second half, see "simple transformation". But the first half is relevant, and worth editing in to the "Not a dupe" sentence. 3. I still can't figure out the output format from the examples. Obviously you want to ensure that it's not as trivial as asking the regex engine for group 0, but I think you need to first write a clear spec for the output and then write the examples (or, better, write a reference implementation to generate the examples). Nov 6 '15 at 7:27
• @PeterTaylor, yeah, I'll have to work on it some more. If anyone else has ideas, please chime in! Nov 6 '15 at 9:24

# Python assembler

Python is a hybrid interpreted language. It first gets compiled into byte-code and then gets interpreted.

What does this byte-code look like you may ask? The dis module disassembles python code. Source code for dis module here

print "Hello, World!"


Gets disassembled into the following assembly.

  1           0 LOAD_CONST               0 ('Hello, World!')
3 PRINT_ITEM
4 PRINT_NEWLINE
8 RETURN_VALUE


The output is divided in the following columns:

1. the line number, for the first instruction of each line

2. a labelled instruction, indicated with >>,

3. the address of the instruction,

4. the operation code name,

5. operation parameters, and

6. interpretation of the parameters in parentheses.

The disassembly of a basic for loop

for i in range(10):
print i


gives

  1           0 SETUP_LOOP              25 (to 28)
9 CALL_FUNCTION            1
12 GET_ITER
>>   13 FOR_ITER                11 (to 27)
16 STORE_NAME               1 (i)

22 PRINT_ITEM
23 PRINT_NEWLINE
24 JUMP_ABSOLUTE           13
>>   27 POP_BLOCK
31 RETURN_VALUE


Given some python code that has been disassembled, recreate the original code object as close as you can. You can take the disassembled code through any method you chose.

Your program will output all the arguments to recreate a python code object

That is to say your program will output the following

0,
0,
nlocals,
stacksize,
0,
codestring,
consts,
names,
varnames,
"a string here",
"another string here",
0,
lnotab,
(),
()


You can work out the variables listed above but you have to output it all, even the constants.

• nlocals - The number of local variables
• stacksize - The maximum number of values held on the stack at once
• codestring - A binary containing all the opcodes and their arguments
• consts - A tuple of constants
• names - A tuple of global variables
• varnames - A tuple of local names (length of nlocals)
• lnotab - A tuple containing a map of bytecode positions to line numbers

You may use the following code to disassemble a .pyc file:

import sys, dis, marshal

with open(sys.argv[1], "rb") as code_f:
code_f.read(8) # Magic number and modification time
dis.dis(code)


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

## Sandbox notes

Wow that was a long one. Perhaps too long?

Is the spec completely tight?

Should I explain anything further?

Am I making it too hard for non-python entries to take part?

Should I only make it a requirement to reassemble code without any functions/classes? I'm pretty sure dis doesn't show all that.

• For one thing, yes this looks very hard for non-Python entries to me. For another, I think there's too much going on at once (there's a lot to output), and you don't explain much about how to output each specific component (ideally the post should be self-contained enough to work out what to do without knowing too much about Python/dis) Nov 9 '15 at 15:41

# Print a sourcecode

Given 2 inputs(First input is truthy/falsy, second input is program in same language as submission):

1. If the first input is truthy then transform the second input into same program but printing the source code(After modification) first.
2. If the first input is falsy then transform the second input into same program but after the program finished it prints the source code(After modification). If the program doesn't halt, you may or may not modify the program.

It's code-golf, so the shorter answer is the winner.

For example in CJam, I don't write the program to do this. (> means output)

0 q
>{"_~"q}_~
0 0 1{_@+}11*;
>{"_~"0 0 1{_@+}11*;}_~
1 q
> {q](\o"_~"}_~

• Sorry, I'm not quite sure what this question is asking. Would it be okay if you posted examples? Nov 5 '15 at 14:29
• @Sp3000 Please undo your downvote. The example is fixed. Nov 7 '15 at 7:39
• I didn't downvote though... Nov 7 '15 at 8:13

# Vigenère Cipher

Write a program that is capable of breaking a text encyripted using Vigenère cipher encyription.

### Goals:

• Take encripted text from STDIN and write plaintext to STDOUT.

### Limits

• Keyword will always be 3 letters in length.
• Plaintext will always be in between 5-10 letters in length (inclusive).
• All Plaintexts, Keywords and Encyripted Texts will be in English.

### Scoring:

This is a . Shortest code in bytes wins.

I'm not sure if this is a valid and solvable question, so any suggestions are welcomed.

• Dupe
– user45941
Nov 10 '15 at 18:19
• I'm not sure this can actually be done without having a big dictionary for such a short piece of text. (Also, what does "encrypted texts will be English" mean?) Nov 15 '15 at 15:01
• @PaŭloEbermann It means they will only contain english characters, no special letters from other languages. Nov 15 '15 at 15:12
• Then write "consist of the letters A-Z" instead (or similar if you allow spaces and punctuation – though that needs more specification). Nov 15 '15 at 15:14
• For Vigenere, in general you can either try a "plaintext dictionary attack" (which means you'll have a list of valid plaintext words, like in the question linked by Mego – that would be a plain duplicate), or you try analysis of character frequencies or repetitions, which need a lot longer ciphertext in order to analyze anything useful. (Or you just output all possible plaintexts, and let the task of recognizing the correct one to some human.) Nov 15 '15 at 15:19

# List Style Converter

[code:golf]

Given a list, format it into list of the choice of the input. The list will be list of item defined below, but it can be multidimensional.

## List Styles

There is 2 list separators:

1. Space
2. Comma

For one dimensional list, only one separator is accepted. Space and only space between item is considered as separator. It is impossible to have more than 2 dimension without enclosing list of second dimension or third dimension. when parsing list, comma takes lower precedence and it is parsed with least dimension as possible. Space is optional between ] with [; } with {; and ) with (

There is 3 list enclosure:

3. [...]

4. (...)
5. {...}

Closing bracket must be present.

## Item

There is 2 types of item, another list or those following regex [0-9a-zA-Z]* or everything enclosed with single quote or double quote. If enclosed with single quote, it can contains double quote and vice versa. There is no zero-length item

Here is valid non-list item

98Az
Helloworld
"Hello, world!"
"It's house."


Here is the list

Hello, World!
Space then it is list
()


Here is invalid item.

!$%#%^$*%%^&%^&\$%#:;,./<>?
Helloworld!


## Input

The input consist of string of number then space then list as defined above. The number indicates the output format.

There are n digit of number where n is dimension of the input array. each number correspond with this one. (Table formatting needed). The dimension is counted from outer into inner. You may assume that there is no two 0 or 1 without being separated by 2 - 7.

1. 0 = unenclosed comma list
2. 1 = unenclosed space list
3. 2 = parantheses enclosed comma list
4. 3 = parantheses enclosed space list
5. 4 = square bracket enclosed comma list
6. 5 = square bracket enclosed space list
7. 6 = curly bracket enclosed space list
8. 7 = curly bracket enclosed space list

## Output

A identical list but with formatting changed according to input (i.e. each item it list is identical). Space not between list is allowed

## Test cases

> denotes output # denotes comment

6 Hello, world
> {Hello world}
5 (1, 1, 2, 3, 5, 8, 13, 21)
> [1, 1, 2, 3, 5, 8, 13, 21]
#Alternatively
> [1,1,2,3,5,8,13,21]
#Or
> [ 1,1, 2,3, 5,8, 13,21 ]
#But it is invalid
> [1,1, 2,3, 5,8, 1 3,2 1]
#Also
> [1,1,2,3,5,8,13,21,]
10 Hello, I am doctor
#Parsing rules that space separator bound tighter
> Hello I,am,doctor
01 Hello, I am doctor
> Hello, I am doctor
0 "Not to be confused be space or comma in a quoted item"
> "Not to be confused be space or comma in a quoted item"
51 [1,2] [3,4]
> [1 2,3 4]
51 [1,2][3,4]
> [1 2,3 4]


## Sandbox Question.

The format needs helps. Needs pointing when there is ambiguity.

• I'm not sure that I fully understand this. To take a couple of your examples, Hello, World! appears to have two separators (a comma and a space): is it a one-dimensional three-element list, or a two-dimensional list? Is () a one-dimensional list or a two-dimensional list? And in the input, which order are the dimensions listed in, and what constraints are there on which formats can be used at which levels? (E.g. 00 is clearly not going to work, but I'm not sure whether 010 is permitted). Nov 16 '15 at 23:20
• @PeterTaylor That's why I post the challenge here, because this challenge is nontrivial to writing. It is one dimensional comma separated list. Only space between item is list separator. Comma (except inside quote) isn't valid part of item. The input order is from outer into inner. You can assume that 00 and 010 isn't never entered. Nov 17 '15 at 8:35
• () is one-dimensional list since you have to it is parsed with least dimension as possible Nov 17 '15 at 8:43
• I'm afraid that I'm even more confused than before about spaces and commas. You seem to be saying that in the example 6 Hello, world a (comma plus space) makes a single separator in a one-dimensional list, whereas in 10 Hello, I am doctor a (comma plus space) is two distinct separators in a two-dimensional list. Do you have a reference implementation which we might be able to use to reverse-engineer the spec while the question is still in the sandbox? Nov 17 '15 at 16:55
• In "Hello, world", "Hello" and "World" can be 1-item space separated list, however, lowest dimension takes precedence. In "Hello, I am a doctor" It is list containing 2 item. One is 1-item list, other is 4-item list. Nov 18 '15 at 9:56

# Triangularity

This is a challenge where you have to work out the length of a given w and h.

To qualify as a correct solution:

1. The program uses STDIN to get the values of w and h.
2. The program uses STDOUT to output the value of a in the above diagram.

The shortest code in bytes wins.

Tags: code-golf, maths

• What's the formula? Unless it's very complicated, I expect it will be totally straightforward to golf.
– xnor
Nov 18 '15 at 11:45
• @xnor, a = w/2 * sin(atan(h/w)). The diagram throws in some irrelevancies and omits a relevant line, but it's not an interesting problem. Nov 18 '15 at 13:02
• @Peter Should I post this or do you think it's too easy? Nov 18 '15 at 21:31
• @Tobsta I think it's too straightforward. Languages with trig will use the formula Peter gave, and the rest will do something like h*w/sqrt(h*h+w*w)/2.
– xnor
Nov 18 '15 at 21:58
• @xnor Ok, got it Nov 18 '15 at 22:54

# Introduction

I've read this problem long time ago somewhere but I still don't know what's the best solution, so I'm posting it here. I don't remember the original author or wording so here is all in my own words.

This is different from regex golf because only two wildcards, * (equivalent to the regex .*) and ? (equivalent to the regex .), are allowed.

# Challenge

You are given two lists of strings. You need to generate the shortest wildcard that matches all strings in the first list (the wanted-list) and none in the second list (the unwanted-list). In the wildcard, you can use * to match 0 or more chars and use ? to match any one char.

For simplicity we can assume that inputs only have lowercase English characters and each string won't be longer than 100 characters. But the list can be very long (like several thousand), so speed of your program is important.

The correct answer that has the lowest average-case theoretic time complexity wins. In a tie, an easier-to-read answer wins.

# Example Input and Output

Input:

One possible output: a?a*
• Ah, I thought you were using wildcard as a synonym of regex. I take the point that removing alternation does make quite a different problem. Although it has the downside that there are insoluble cases (e.g. I don't think your wildcards can separate a wanted list of a and abba from an unwanted list of aba), so you'd need to specify how those cases should be handled. Nov 17 '15 at 22:16