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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.

To post to the Sandbox, scroll to the bottom of this page or click on the "Add Proposal" link below, and click "Answer This Question". Click "OK" when it asks if you really want to add another answer. Write your challenge just as you would when actually posting it. 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, replace the post here with a link to the challenge and delete it.

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

The Sandbox works best if you sort posts by "active".

Add Proposal

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Browse your pending proposals

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

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  • \$\begingroup\$ How are tags added to questions? \$\endgroup\$ – guest271314 Jan 9 at 7:51
  • \$\begingroup\$ @guest271314 You can use this markup to create a tag in a draft: [tag:code-golf] \$\endgroup\$ – DJMcMayhem Aug 29 at 15:19
  • \$\begingroup\$ Why no featured anymore? Can't we have it auto-added or something? \$\endgroup\$ – JL2210 Sep 26 at 15:57
  • 1
    \$\begingroup\$ @JL2210 We now have a permanent info box that links to the Sandbox, so the featured tag isn't necessary \$\endgroup\$ – caird coinheringaahing Sep 29 at 13:43

2579 Answers 2579

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Normal quine, weird quine

Note: This Sandbox entry has a fairly long history, and is basically an attempt to produce a challenge inspired by this comment, but that's immune to wilful misinterpretation (or misunderstanding) of what counts as an error in order to trivialise the question.

Background

In the world of programming languages, there are lots of different ways to produce output on the usual output streams. Most languages have a way to print a string intentionally, called print, write, or something like that. Sometimes you can even just leave a value to be printed implicitly. Most languages also have situations in which the implementation interjects with its own output, e.g. warnings produced during the compile. We'll call this weird output.

Task

For each method of output to standard output or standard error in a programming language, consider how much of that output is under the programmer's control and thus can contain arbitrary text (e.g. specified as a parameter, part of the program's filename, taken from a variable that can be assigned to, or the like), as opposed to being a single possibility (or a finite set of possibilities) hardcoded into the interpreter. We'll call this output method normal if no more than 3 bytes are outside the programmer's control; and weird if there are 4 or more hardcoded bytes that the programmer cannot control.

In this challenge, you need to write a full program that's a variant, obeying the proper quine rules. Specifically, after performing the entire process of building and running the program (i.e. if there's a separate compile step required, its output counts too):

  • All the output produced on standard output and standard error via normal output methods must be identical to the program's source code;
  • All the output produced on standard output and standard error via weird output methods must also, separately, be identical to the program's source code.

In other words, the program is a quine in two different ways. You can think of this as being a quine that's also an error quine (also known as a "Kimian quine"), except that the notion of "error" is restricted in order to avoid abuse (mechanisms which would let the program provide an arbitrary "error message" count as normal output, not weird output, on the above definition), but generalized to allow things like warnings, banners that the implementation prints as it loads, and other weird ways to produce output.

Clarifications

  • For the purpose of the proper quine definition, the fixed part of the output that's inherent in a weird output method is considered to not be encoded by the corresponding part of the program (even if that part of the program causes an error). As such, only the normal part of the quine can fail to be a proper quine.
  • PPCG doesn't normally count output that's inherent to an implementation (such as compiler progress messages and fixed banners). This challenge is about handling that sort of thing, though, so such output is definitely relevant here (in addition to everything else on the standard output and error streams).
  • Unlike in many challenges, the switches given to the compiler, and the program filename, are likely to be highly relevant in this challenge. Using an unusual build configuration may well be required to make the challenge possible, and as such is legal here; however, if you run the implementation in an unusual way, remember that PPCG rules charge a byte penalty for doing so (equal to the number of additional characters that you'd need to add on the command line over the shortest "normal" way to run a program), and thus you'll need to specify the size of the penalty in your post. (For example, if the interpreter you're using reads the program from a file, and has no particular restrictions on the filename, the shortest normal way to run the program would be from a file with a 1-character filename; thus, if you need a 100-character filename to make your program work, you'd incur a byte penalty of +99.)
  • The compiler/interpreter version you use may well be relevant, so as part of your submission, please state a specific compiler or interpreter on which your program works, and which version is required. (For example, a C submission might state "C (gcc 6.2.0)" in the header.)
  • Note that this task may not be possible in all languages. In the languages where it is, the easiest method will likely be to find an error or warning message for which it's possible to customize some subset of the text (via changing the name of something that gets quoted in the message; filenames are a common choice here, but not the only one). Obviously, if you could customize the entire thing, it wouldn't be weird output and thus wouldn't work. I'll be particularly impressed (and surprised) if someone finds a way to do this using only error and warning messages whose text is entirely fixed.

Victory condition

This is a challenge, so an entry is considered to be better if it has a smaller byte count. As such, once you've got your program working at all, you want to optimize it to bring the number of bytes down as far as possible. (However, don't be discouraged if there's already a shorter entry, especially if it's in a different language; what we're really looking for here is to shorten a particular algorithm or idea behind a program as much as possible, but seeing multiple solutions in different languages or that rely on different principles is always worthwhile.)

Sandbox questions

This was moved here from main because many answerers seemed to disagree with everyone else as to what an error message was.

I've aimed to avoid the problem in this rewrite by focusing not on what is and isn't an error message, but rather on the amount of hardcoded content in the message. Is this likely to be interpreted the same way by everyone? Is it objective?

Also, should I edit the original challenge, or should I post it as a new challenge? Out of the two non-deleted answers, one will stay valid (although the explanation will end up somewhat out of context), the other will need to be deleted (although I consider it to be invalid under the original specification too, and thus arguably no changes are being made to which answers are correct).

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Multiplivision

Hopefully a nice simple challenge that's not trivial.

Given an input list of positive integers, alternately multiply and divide them to yield a single numerical answer, according to the following rules:

  • start with the first number;
  • with the remaining numbers, alternate between dividing and multiplying, one at a time (that is, in a left-associative way), with the last operation being multiplication

For example, the input {3, 4, 2, 7} would start with 3, then successively compute 3 * 4 = 12, then 12 / 2 = 6, then 6 * 7 = 42 and output 42. (In other words, the input {3, 4, 2, 7} yields the output (((3 * 4) / 2) * 7) = 42.) The first operation had to be a multiplication, because if we'd started with a division, then the last operation would have been division as well, which isn't right.

If the answer is not an integer, then it can be output either as an exact fraction, or as a decimal equivalent, accurate to at least 6 significant figures (either truncating or rounding the end of the decimal is fine). For decimals that terminate before 6 significant figures, either the terminating decimal alone (1.5) or a version with trailing zeros (1.50000) is fine.

Other test cases (only the numerical answer needs to be output, not the intermediate parsed expression):

{3} -> 3
{3, 4} -> 3 * 4 = 12
{3, 4, 2} -> 3 / 4 * 2 = 3/2 or 1.5
{5, 4, 3, 2} -> 5 * 4 / 3 * 2 = 40/3 or 13.3333
{1, 2, 3, 4, 5, 6, 7, 8} -> 1 * 2 / 3 * 4 / 5 * 6 / 7 * 8 = 128/35 or 3.65714
{42, 42, 42, 42, 42, 42} -> 42 * 42 / 42 * 42 / 42 * 42 = 1764
{42, 42, 42, 42, 42, 42, 42} -> 42 / 42 * 42 / 42 * 42 / 42 * 42 = 42

This is , so the shortest code in bytes wins! Golfed answers in all languages are welcome.

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  • \$\begingroup\$ accurate to at least 6 significant figures (including decimals that terminate before the 6th significant figure) In the 3rd test case, shouldn't it then be 1.50000 as it has to be 6s.f.? \$\endgroup\$ – Thunda Mar 29 '17 at 3:21
  • \$\begingroup\$ thanks, clarified above \$\endgroup\$ – Greg Martin Mar 29 '17 at 3:22
  • \$\begingroup\$ In most languages that happens automatically, I really don't think it's necessary \$\endgroup\$ – Thunda Mar 29 '17 at 3:40
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King of the Hill: Risk(k)

We all know these well spend evenings where family members and friends got to temporary enemies while playing Risk the board game. The rules are not so complicated, the world is divided in territories on 6 different continents. enter image description here The different players take control over those territories and afterwards play to conquer the neighbors, form alliances and betray each other until one player reaches world domination.

But wouldn't it be cool, if you just write a bot for you to play this game? here comes your chance.

This is a King of the Hill challenge to write the best bot to play Risk(k). Like in the original game (but not entirely) the world is divided into 6 continents with a total of 41 territories. Afterwards the bots will play this game with reduced rules in a round-based setting. Your bot can be written in or . Although any other language is possible which is capable of producing a dll with cdecl-functions or to implement interfaces. The controller can be found on Github.

enter image description here

A short classis-game explanation

For all of you, who aren't familiar with this game. Every player plays on his own against all other players. The game begins with the claiming of territories (by positioning a single unit there) which is done consecutively for every player until all territories are owned by a faction. Now the players get the chance of using all units they have left to enforce their territories. Now the game begins round-wise. Every player makes a Attack-Stage and Move-Stage. In the attack-stage the players can attack other territories. This is done with dices. When thrown (the attacker and defender), the dices on each side are ordered and the highest ones are compared to each other. Whoever has the higher dice destroys a unit of the opposite side. Equal dices are considered a tie and no unit dies. You can only attack with max. 3 units at the same time, even when you have more than 3 units on your attacking territory. Also a territory with one unit cannot attack to prevent territory loss. Likewise a territory with two units can only attack with one etc. . When a territory falls to zero units, the attacking territory has to send units over (at least on and max. all except one - in the controller, all units except one are send automatically). After the attack stage, one player gets the chance to move units in the Move-Stage. One can only do so, if the territories you want to move units between are connected by territories owned by you. If your are done with this, the next players turn begins. The game ends, when one player has conquered the whole world.

The game&rules:

  • All bots have to obey the rules. Cheating bots will be punished by the program or by me. Standard loopholes are forbidden.
  • Each bot must be in a dll file (name.dll) in the same directory, as the controller.
  • Each program with the c++ interface must end with name.cpp.dll
  • When the program is started each bot gets loaded into the program and is checked if everything works. The bots get instantiated only one time when the game starts.
  • All bots loaded are participating in the game.
  • The initialization stage begins:
    • Each bot gets asked through the interface about its name and color.
    • All bots get introduced to another with their names.
    • All bots get consecutively called to select one of the remaining free territories. This goes till no territory is free anymore.
    • All bots get to distribute the units left to all territories. [UnitCount = Ceil(82 / BotCount) ]
  • The game will stop for now till the user pushes the start-button.
    • The game will be round based where each bot will get consecutively called in four stages: Strategy-Stage, Enforcement-Stage, Attack-Stage, Move-Stage
    • The Strategy-Stage gives your bot the opportunity to plan a strategy for this round.
    • The Enforcement-Stage will give your bot the opportunity to distribute all new units to your territories. Units are gained to: Count of owned territories divided by 5 and floored, continent-bonus (owning a whole continent: North America: +5, South America: +2, Europe: +5, Africa: +3, Australia: +2, Asia: +7), capital-bonus (+1 for each owning of: East US, Brazil, North Europe, South Africa, East Australia, China) and +1 if you conquered a territory last round. You're guaranteed to get at least one new unit per round if your bot is still alive.
    • In the Attack-Stage you can order the program do make attacks on enemy territories which can lead to loss on your or the enemy side or you conquering a new territory. The attack will be called multiple times (max.: 100 times) as long as you make an attack every call.
    • In the Move-Stage you can move units around owned, connected territories. You can also again plan your strategy there for the next round.
    • Each round is time constricted for every bot with 200ms. Taking longer than this will lead to a punishment (suspension) for the next round.
  • The game ends when only one bot still lives or when two bots get into an infinite loop (which is surprisingly possible and not rare for the random-bots)

The controller&interface

How the interfaces work is explained in the template files and the example-bots.

For c#, .NET Programmer

Your bot has to be in a class which inherits and fully implements the IBotInterface. The class must be compiled into a class-library (dll). Afterwards you can just copy your dll into the game-directory and start the game.

EmptyBot is an empty template which implements the minimum required and adds a lot of useful helper-methods. It can be used as a template.

RandomBot is a bot which implements random behavior in all functions and stages. It acts as a full working example.

For C++, C, cdecl-function-able-languages

Your dll must implement eight functions with an external definition and cdecl-calling convention. A minimal implementation can be looked at at EmptyCPPBot.

Your dll can afterwards be copied into the game-directory which can be started normally afterwards. Your dll must have the following name structure: nameOfYourDll.cpp.dll to distinguish it from the managed dll's.

RandomCPPBot is a bot which implements random behavior in all functions and stages. It acts as a fully working example.

Contest Rules

  • Players may submit multiple bots and are free to edit them to the deadline.
  • A submission must be made as an answer on this thread. The source code can come in pieces, as full project, single file or whatever. And may be provided via download, push request or simple pasted code in the answer with code-tags. If not compile-able with Visual-Studio, i request fairly simple instructions how to compile it myself.
  • A submission must specify the name and color of the bot. Although not necessary, an explanation of the bot's strategy would be nice.
  • Bots are not allowed to use sources outside the dll/program (no files, no webrequest or similar things).
  • Bots must be compatible with the provided interface and work under windows. Custom interfaces are not explicitly forbidden as long as they don't generate a advantage or are not compatible with the main-interface/program.
  • The competition will be held in the provided controller (possible altered to automate the process) with all pairings possible to find the best 4 bots.
  • The last 4 bots are fighting each other in 10 games. The bot which has won the most, wins the tournament. In a tie situation, the bots will take a single match against each other (golden goal), until one wins.
  • Rules are can be changed when necessary which would be introduced on top of this thread.
  • The contest ends when a week long no new submissions got made or when I say, its time to end this.
  • And again, just to be sure: standard loopholes are forbidden.
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  • \$\begingroup\$ How do you organize players into games, how do you score a single game, and how do you aggregate those scores? When are you instantiating each bot (only once for the tournament, once for each game, or once for each method call?) I'd recommend describing the rules of risk in full for those poor souls that don't know them. \$\endgroup\$ – Nathan Merrill Mar 30 '17 at 21:45
  • \$\begingroup\$ I added a relative "short" description of the classical game. Also I added the answer to all your question into the thread but i'll also anwser it here: 1. All players in the game directory are participating. The tournament will provide automatic pairings if necessary. 2. You score a single game by letting your bot win it. 3. You can't. But you can restart infinitely often. 4. All bots are instantiated on the start of the program. But i could change that to the start of every game (so a reload also instantiate the bots new). \$\endgroup\$ – Julien Kluge Mar 30 '17 at 22:35
  • \$\begingroup\$ 1. What if there are lots of players (10 or even 20?). How would you automatically pair? 2. So the second to last survivor gets the same number of points as the first one to die? What happens if there's an infinite loop? 3. You have to come up with some way to combine the scores across multiple games. 4. Are you OK if submissions store data across games? How do submissions know when a new game starts? \$\endgroup\$ – Nathan Merrill Mar 30 '17 at 22:46
  • \$\begingroup\$ Risk is a famously unbalanced game in which luck is very important. To balance that out you'll need to play hundreds of games per match-up. Each game involves thousands of player decisions. I would not be surprised if it ends up taking a week to run the tournament, and part-way through that week someone might submit a new bot. \$\endgroup\$ – Peter Taylor Mar 31 '17 at 12:31
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Check for repeated repeated words

Task

Your code should either read in a stream/file containing printable ASCII text or define a function that takes a string containing printable ASCII and output any repeated words (including their repetitions). If you read from a file then it can have a name of your choice. Output can be a single linefeed-separated string, or a list of strings (one per repeated word).

A word is defined by the regex [0-9A-Za-z'-]+, i.e. it's a run of letters, digits, apostrophes and/or hyphens.

A word is considered to be repeated if it occurs twice or more in succession, separated only by one or more spaces. Repetition is case sensitive: WORD, Word and word are all different.

Test Cases

Individual test cases are separated by an empty line. For each test case, the first line is the input, subsequent lines are the output. Note that the last test case does not contain any repeated words.

Hello how how are you?
how how

Hello my my friend. Is that that your pen pen pen?
my my
that that
pen pen pen

This is not. not a case of repeated? repeated words! Neither neither is this. 

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  • \$\begingroup\$ Why do you disallow functions? \$\endgroup\$ – mbomb007 Mar 31 '17 at 16:08
  • \$\begingroup\$ @mbomb007 I don't :) \$\endgroup\$ – user9206 Mar 31 '17 at 16:13
  • \$\begingroup\$ "No other ways of getting input are allowed." Which means function arguments. \$\endgroup\$ – mbomb007 Mar 31 '17 at 16:16
  • \$\begingroup\$ @mbomb007 That text shouldn't have been there. Thanks. \$\endgroup\$ – user9206 Mar 31 '17 at 16:23
  • 3
    \$\begingroup\$ If underscores aren't a valid word character for this challenge, you'll want to add a test case that has underscores. I can see a lot of regex submissions being based on \w otherwise. \$\endgroup\$ – DLosc Mar 31 '17 at 17:17
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    \$\begingroup\$ REgex would would win \$\endgroup\$ – Christopher Mar 31 '17 at 20:28
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Island Golf #3: Random Generation

Given the dimensions of a rectangular patch of ocean and the desired number of land tiles, randomly generate a valid island of that many tiles within that rectangle.

Input

Your input will be three positive integers:

  • w, the width of the grid
  • h, the height of the grid
  • n, the number of tiles to make the island

w and h will always be 3 or greater. n will always be 1 or greater. Also, n will be small enough to fit inside the grid allowing for a border of water tiles: specifically, n <= (w-2)*(h-2).

Output

Your code must output a w by h rectangular grid consisting of two characters, representing land and water. (In the examples below, land is # and water is ., but you may substitute any two distinct characters you wish.) There must be exactly n land characters, in one contiguous block, representing an island. For example, an input of w=11, h=9, n=40 might result in the following output:

...........
...##......
..#####....
..#######..
.#########.
...#######.
...#####.#.
....####...
...........

Requirements:

  • The land tiles must all be contiguous (i.e. there's only one island).
  • Land tiles can be connected horizontally or vertically, but not diagonally.
  • The water tiles must also be contiguous (i.e. there must not be any lakes).
  • The outer border of the grid must remain as water tiles.

Some illegal outputs:

.....
.#.#.   Multiple islands
.....

....
.#..    Diagonal connection
..#.
....

......
.####.  Contains a lake
.#.##.
.##...
......

....
.###    Border contains a land tile
.##.
....

Details

Your solution may be a full program or a function. Any of the default input and output methods are acceptable. Any of these definitions of randomness are acceptable. Every valid island for a given input should occur with nonzero probability.

You may take the input numbers in whatever format and base is convenient for your language. You may take the three numbers in any order.

Your output may be a multiline string, a list of strings, or a 2D array/nested list of characters/single-character strings. Your output may (optionally) have a single trailing newline. As mentioned above, you may use any two distinct characters in place of #..

Please mention any unusual I/O methods/formats in your submission, so others will be able to test your code more easily.

Test cases

Given as width, height, size. Note that the first three test cases specify islands of maximal size for the given width and height.

3, 3, 1
9, 3, 7
5, 5, 9
5, 5, 1
10, 10, 60
80, 22, 1100

Validation program

Here is a validation program in Pip to test whether your output for a given input meets the spec. It expects the three parameters and an island in the format given in this question; for example:

5, 5, 9
.....
.###.
.###.
.###.
.....

If your code has a different output format, you'll need to convert it to this format before plugging it into the validation program.


Sandbox questions:

  • This seems like a pretty obvious random-generation challenge, but I didn't find a duplicate in a quick readthrough of previous challenges. Did I miss anything?
  • Should I add more stringent rules on what counts as random? Related reading
  • Should I allow output to be a 2D array (or nested list) of any two distinct values, not just chars and single-char strings? (E.g. integers 0 and 1, booleans false and true, etc.)
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  • \$\begingroup\$ To the downvoter, if you see this: What's your reason for downvoting? If it's something I can improve about the challenge, I'd like to know so I can improve it. \$\endgroup\$ – DLosc Apr 6 '17 at 1:28
1
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Calculate Wind Chill


The Australian Apparent Temperature (aka, wind chill) in °C AT is given by this algorithm from the Australian Bureau of Meterology (wp, source):

enter image description here

AT = Ta + (0.33 * e) - (.7 * ws) - 4.0

Where:

Ta = Dry bulb temperature (°C)

e = Water vapour pressure (hPa)

ws = Wind speed (m/s) (at an elevation of 10 meters)

The water vapour pressure in hectoPascals e is given by this algorithm:

enter image description here

e = (rh / 100) * 6.105 * exp( ( 17.27 * Ta ) / ( 237.7 + Ta ) )

Where:

Ta = Dry bulb temperature (°C)

rh = Relative humidity [%]

exp represents the exponential function

The domain of:

  • Ta is -273.15°C to 2e7°C.

  • e is the real numbers

  • ws is 0 m/s to 2e7 m/s

  • rh is 0% to 100%

For inputs outside these domains, your code can do anything, including give the right answer.


Output

Given a dry bulb temperature in °C, a wind speed in metres / second, and a relative humidity in %, your code should give the Apparent Temperature in °C, accurate to 0.1°C.

Assuming your platform or language can represent reals, for correct functions correct_func,

enter image description here

or in C, fabsl( correct_func(Ta, rH, ws) - expected ) < 0.1.

Test cases

value for Ta, rh, ws -> output

0   ->  -4.0
2   ->  -3.3529916671770903
4   ->  -2.6916697830145546
6   ->  -2.0132006039049877
8   ->  -1.3143308806029346
10  ->  -0.5913412821173161
12  ->  0.16000376605969002
14  ->  0.9445099696431676
16  ->  1.767610915646344
18  ->  2.6354298170017625
20  ->  3.5548453789325833
22  ->  4.5335619088440815
24  ->  5.580183785538598
26  ->  6.704294397098089
28  ->  7.916539649854112
30  ->  9.2287161435045

You can use a builtin function for the exponential function, ex, if you like.

This is , so the shortest code wins!

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1
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Factor Sort

This challenge involves sorting positive integers based on a lexicographical ordering of their prime factorizations.

Overview

lexicographical sorting, used in dictionaries, applies lexicographical order which extends alphabetical order to words:

a
aa
aaa
aaron
ab
abandoned
abc
aberdeen

When programming this sort, however, we typically don't extend alphabetical ordering per se, but rather we extend the order of integers used for an encoding. For example, the same sorting above through ASCII encoding is really:

97
97 97
97 97 97
97 97 114 111 110
97 98
97 98 97 119 100 111 110 101 100
97 98 99
97 98 101 114 100 101 101 110

It is this type of ordering that we're after here... lexicographical ordering by extension of numeric comparison as opposed to alphabetical order.

The Challenge

In this challenge, you will be sorting positive integers by their ordered prime factorizations (ordered in the sense that the primes are listed smallest to largest). To handle the special case number 1, we can simply say its prime factorization is an empty list, which lexicographically sorts prior to any other number's prime factorization. We'll call this type of sorting factor sorting.

For example, the numbers from 1 to 10, factor sorted, are: 1 2 4 8 6 10 3 9 5 7. To see why, here they are again with the ordered prime factorizations:

 1 []
 2 [2]
 4 [2 2]
 8 [2 2 2]
 6 [2 3]
10 [2 5]
 3 [3]
 9 [3 3]
 5 [5]
 7 [7]

Rules

Write a function or program that factor sorts a list of positive integers. Input and output can be anything reasonable, so long as the input is in the specified arbitrary order and the correct output order is apparent from the output.

Keep in mind that the output should be factor sorted numbers, not their prime factorization.

If it matters, numbers in the input will always be ≤ 7928, so:

  • The only primes in the prime factorization list are the first 1000 primes
  • Composites have factors no larger than 89 inclusive

This is code golf; shortest code in bytes wins.

Test cases

1 2 3 4 5 6 7 8 9 10
->
1 2 4 8 6 10 3 9 5 7

100 200 300 400 500 600 700 800 900
->
800 400 600 200 900 300 100 500 700

1472 4417 1425 1452 4480 200 339 2868 3835 4760
->
4480 1472 200 4760 1452 2868 1425 339 3835 4417

2 4 6 46 62 466 622 4666 6238
->
2 4 6 46 62 466 622 4666 6238

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  • \$\begingroup\$ This is extremely trivial in golfing languages (e.g. in CJam it's {{mf}$}), so may attract negative attention and may not attract answers in any language in which it's an interesting challenge (if there are any). \$\endgroup\$ – Peter Taylor Apr 3 '17 at 11:27
  • \$\begingroup\$ I think asking to compare two numbers makes for a nice challenge than sorting them. Implementing sorting based some a key function has been overdone, and many languages just have a built-in for it. Also, I suspect there are strategies for comparison that do not compute the factor vector. \$\endgroup\$ – xnor Apr 3 '17 at 22:27
  • \$\begingroup\$ @xnor "I suspect there are strategies ..." I'm confused about what you're trying to convey here. Granting your suspicion... suppose there's indeed another way to meet the specification. Why would that matter? \$\endgroup\$ – H Walters Apr 4 '17 at 3:05
  • \$\begingroup\$ @HWalters I mean that a challenge to simply compare rather than sort might allow a wider variety of solution strategies, which makes it more interesting to golf. \$\endgroup\$ – xnor Apr 6 '17 at 1:59
  • \$\begingroup\$ Is this in the OEIS? \$\endgroup\$ – dkudriavtsev Apr 19 '17 at 6:12
  • \$\begingroup\$ @Mendeleev Not sure how to answer this. Strictly no, since it's not a sequence. If we factor sort all positive integers, then we get an infinite number of infinite "chains" of numbers, each chain of which is ordered. The first such chain is A000079, powers of two, so if you stretch you could say this is A000079. Powers of 3 excluding 1 is another chain after this; 2 times powers of 3 excluding 2 (i.e., 6, 18, 54, ...) is another chain between the two; etc. There's no "second chain" (chain immediately after A000079), and no immediate predecessor chain to powers of 3 excluding 1. \$\endgroup\$ – H Walters Apr 19 '17 at 15:01
1
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Dice Roller

Since I have played a lot of tabletop role playing games, I am looking for an easy to use dice roller. But also being lazy, I would like to have the shortest possible solution, making this code-golf.

Input

You will receive as input a string, composed of 2 or 4 variables.

In the case of 2 parameters, both non-negative numbers, they represent the number of dice and the value of the dice rolled.

Examples:

"2 6" means rolling 2 6-sided die (colloquially written 2d6).
"3 8" means rolling 3 8-sided die (3d8).

In the case where 4 parameters are given, the first 2 are still numbers, as in the case of 2 parameters. The third and forth parameters represent a dice modifier, and whether the modified applies to the dice individually or the sum of all rolled values, respectively. The third parameter is a (possibly) signed number (e.g.: 2, +1, -2, ...), and the forth is a character string, either 'ind' (if the modifier applies to the individual dice) or 'all' (applies to the total sum of the dice rolled).

Examples:

"2 6 +1 ind" means rolling 2 6-sided die, and a modifier of +1 is applied to each individual die (can be written 2d(6+1)).
"3 8 -4 all" means rolling 3 8-sided die, and a modifier of -4 is applied to the sum of the roll (can be written (3d8)-4).

Dice Properties

  • Only the following dice are acceptable (second parameter): 2 3 4 6 8 10 12 20 100.

  • Regardless of modifier, a dice gives at least a value of 1 when an individual modifier is applied (so for example, "1 6 -10 ind" will return a value of 1, the minimum value allowed by this stipulation). There is no max value to an individual modifier.

  • When a modifier is applied to the sum of the dice rolled (4th parameter is "all"), the sum can be less that the number of dice rolled. For example, "2 6 -20 all" will give a sum range of -18 to -8, as the lowest value of 2d6 is 2 and highest value is 12, pre-modifier. There is no min or max value to a this modifier.

Output

The output will be the values of the individual dice rolled, and the sum of all the dice.

Valid examples:

"2 6" => "3 6 : 9"
"3 8" => "1 8 5 : 14"
"2 6 -1 ind" => "1 2 : 3"
"2 6 -10 ind" => "1 1 : 2"
"3 8 +1 ind" => "2 9 6 : 17"
"2 6 10 all" => "3 6 : 19"
"2 6 -10 all" => "3 6 : -1"

Invalid examples (incorrect results):

"2 6" => "3 7 : 10" (7 is not a valid result on a 6-sided die)
"3 8" => "1 8 : 9" (not enough dice rolled)
"3 8" => "1 8 5 4 : 18" (too many dice rolled)
"2 6 -1 ind" => "1 6 : 7" (6 is not a valid result on a 6-sided die with a -1 modifier applied)
"2 6 -1 ind" => "0 5 : 5" (the die has to have a minimum value of 1 with individually applied modifier)
\$\endgroup\$
  • \$\begingroup\$ There's this. As far as I can tell, the only difference is the exact input format and your fourth parameter. I can't say whether or not people will close it as a duplicate (although there's a good chance they will, because all it does is optionally multiply the bonus by the number of dice), but it might generally be unpopular if the community feels it doesn't add anything interesting over an existing challenge. \$\endgroup\$ – Martin Ender Apr 4 '17 at 18:51
  • \$\begingroup\$ @MartinEnder The forth parameter, limits on which dice can be rolled and the negative value modifiers. As for as I can see, the question you linked to doesn't have any consideration for XdY-Z, which I wanted to include as it introduces the minimum 1 constraint for the dice rolls. But that's why I put it in the sandbox first, to see what the community thinks :) \$\endgroup\$ – AntonH Apr 4 '17 at 18:55
  • \$\begingroup\$ @MartinEnder Would it maybe work if I posted a link to that question, but also specified the differences between the questions? \$\endgroup\$ – AntonH Apr 4 '17 at 18:57
  • 1
    \$\begingroup\$ I personally don't think that the max(1, roll) makes a sufficient difference. I know it's frustrating when you put a lot of effort into a challenge spec and it turns out to have already been done (the same or similarly), but if it's almost the same as an existing challenge, it's usually better to try something else. It's ultimately up to you, of course. \$\endgroup\$ – Martin Ender Apr 4 '17 at 19:06
  • \$\begingroup\$ @MartinEnder It got stuck in my head and wouldn't leave, so I had to get it down :P I'll wait a bit to see if anyone else has anything else to add, but if it doesn't go anywhere, it's fine. \$\endgroup\$ – AntonH Apr 4 '17 at 19:13
  • \$\begingroup\$ @MartinEnder I wouldn't close it as a dupe. They're similar, to be sure, but a big chunk of the linked challenge is input parsing and validation, which isn't present here. I also think that the fourth parameter (ind vs all, though I would suggest to let people use two distinct values rather than string-matching) coupled with the possibility of negative modifiers all combine to make this challenge distinct. \$\endgroup\$ – AdmBorkBork Apr 4 '17 at 19:28
  • \$\begingroup\$ @AdmBorkBork Instead of "ind"/"all", would you suggest numerical (0/1) or letter ('i'/'a'), or something else? \$\endgroup\$ – AntonH Apr 4 '17 at 19:33
  • 1
    \$\begingroup\$ Any of the above. If input parsing isn't the primary goal of your challenge (and it doesn't seem to be), don't limit folks on what inputs they and their chosen language can use best. \$\endgroup\$ – AdmBorkBork Apr 4 '17 at 19:41
1
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Find the Translation Table

Given two strings, find the translation table between the two, if the translation is not possible, output false. Probably most easily defined through examples:

Valid Cases

bat,sap = ["bt","sp"]

sense,12312 = ["se","12"]

rabid,snail = ["rabd","snal"]

Falsy Cases

banana,angular = false (not the same length, impossible).

animal,snails = false (different character patterns, not a translation).

Rules

  • Input may be as a 2 element array or as 2 separate inputs.
  • Output can be as an array, on separate lines or space delimited, but must be similar to how I have it shown.
  • False output may be 0, -1 or false. If your language uses something different, ask.

Sandbox Questions

Should I allow inputs of different length to be part of the translation? This will increase the complexity of the question by 100%. I'd suggest using - as the marker for a removal of a character in the translation to make it work. While it makes it more complicated, if this already exists I planned to use that to avoid a duplicate. Let me know what you think. I really like the extension idea though.

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  • \$\begingroup\$ Would empty string "" be an acceptable falsy output? Or empty list []? \$\endgroup\$ – mbomb007 Apr 6 '17 at 21:50
  • 1
    \$\begingroup\$ Shouldn't the second valid test case be ["sen","123"]? \$\endgroup\$ – Laikoni Apr 6 '17 at 22:46
  • 1
    \$\begingroup\$ 1. The examples suggest, but the spec does not state, that trivial translations should be excluded. Or would ["rabid","snail"] also be an acceptable output for rabid,snail? What about ["rabidz","snailz"]? 2. The comment "(different character patterns, not a translation)" seems misleading to me. E.g. given input abc,ddd I would expect that despite having different character patterns the output should be truthy: to wit ["abc","ddd"]. 3. Does the order of the elements in the translation tables matter? I.e. would ["tb","ps"] be acceptable output for the first example? \$\endgroup\$ – Peter Taylor Apr 7 '17 at 10:03
1
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QR Code Editing: Minimum Change

? This is pretty non-trivial, and finding optimal solutions is probably computationally difficult.

QR codes are a way to represent URLs and other strings of text using a 2D image. What you might not know, however, is that a significant portion of a QR code is error-correction or unused space.

In this challenge, your program will be given a square of 1s and 0s representing a QR code. This QR code may not be functional, or it may be valid or point to some destination. Your program will also receive a string, representing the data that the new QR code should be encoded with. The goal of the program is edit the original QR code to contain the new content, but also to do it with as few pixel-flips as possible.

Here's an image describing some parts of the QR format:

enter image description here

QR code art generator, demonstrating how much of a QR code's space can be modified without changing the content: https://www.qrpixel.com/

Spec is only partially completed, I'll probably have to find some decent resources on QR code formats and error correction.

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  • \$\begingroup\$ sound like it will make an interesting challenge once the spec is fleshed out. I assume you're going to include all the qr code info that we need? \$\endgroup\$ – Liam Apr 9 '17 at 22:36
1
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Pratt certificates

(bumping this proposal to see if there's any interest or comments. If so, speak now; if not, I'll delete)

Your task: write code that generates a Pratt certificate for a prime number, and write code that verifies an existing Pratt certificate.

What's a Pratt certificate?

A Pratt certificate for a prime number p is a proof, of a particular type, that p is indeed prime. Historically, it was used in situations where proving the primality of p required a computation that was slow due to factoring p-1, but verifying the certificate (once the initial computation generated it) was quite fast.

A Pratt certificate for p is a recursive structure consisting of three parts: the prime p itself; a "witness" integer g (which is actually a primitive root modulo p; see the next section for its properties); and Pratt certificates for all primes dividing p-1. The prime p=2 is special: a Pratt certificate for 2 is just 2 itself.

For example, here is a Pratt certificate for p=3911:

{3911, 13, {2, {5, 2, {2}}, {17, 3, {2}}, {23, 5, {2, {11, 2, {2, {5, 2, {2}}}}}}}}

The witness is 13, and the prime factors of 3911-1 are 2, 5, 17, and 23; each of those new primes itself has a Pratt certificate, which are respectively 2, {5, 2, {2}}, {17, 3, {2}} and {23, 5, {2, {11, 2, {2, {5, 2, {2}}}}}. In this last Pratt certificate, the prime factors of 23 are 2 and 11, so a Pratt certificate for 11 must be included, and so on.

How do we generate a Pratt certificate?

Given a prime p, a Pratt certificate can be generated by finding a primitive root g modulo p; factoring p-1 into primes (keeping only one copy of each prime factor); and recursively generating Pratt certificates for every prime factor of p-1.

How do we verify a Pratt certificate?

Given a prime p, a witness g, and the prime factors q1, q2, ... of p-1, a Pratt certificate is verified by checking:

  • that p-1 has no prime factors other than q1, q2, ...;
  • that the power g^(p-1) is congruent to 1 modulo p;
  • that none of the smaller powers g^((p-1)/q1), g^((p-1)/q2), ... are congruent to 1 modulo p; and
  • that each of the Pratt certificates of q1, q2, ... are themselves valid.

Scoring and technicalities

You must write two programs or functions (or one of each): one that takes a prime number as input and returns its Pratt certificate; and one that takes an input formatted like a Pratt certificate and returns a truthy or falsy value depending on whether it is an actual Pratt certificate.

  • You may choose any reasonable format for the Pratt certificate: nested lists (like the examples in this question), indented multiline strings (like the example on the Wikipedia page), or something similar that a human being could be trivially trained into parsing by eye. You may use any reasonable convention for the trivial Pratt certificate for 2.
  • However: whatever format you choose for the Pratt certificate, your certificate-generating code must output the same format that you take as input to your certificate-verifying code. Note that your certificate-verifying code must be capable of verifying any possible Pratt certificate (in your format) for p, not just the one your other program generates for p.
  • If you want, you may write a single program or function that accomplishes both tasks; in that case, your code can either determine which task is being asked of it implicitly from the input, or it can allow the user to instruct it which task to perform in some reasonable way.
  • Regardless of whether you use one or two programs, no calculation can be shared or saved between different runs of the code. The programs must work correctly, on any individual prime input and on any individual certificate-shaped input, if it is the first time that code is ever being run on that system.
  • You don't have to handle bogus input. You may always assume that the input to your first program is an actual prime number, and that your input to the second program syntactically matches your Pratt certificate format.
  • Built-ins that generate or verify Pratt certificates are not allowed. Other types of built-ins (for example, those that factor integers, raise integers to powers in modular arithmetic, find primitive roots) are acceptable.
  • This is , so shorter code (in bytes) is better. If two programs are used, the total number of bytes in both programs is the score; if one program is used, its number of bytes is the score.

Example Pratt certificates given prime inputs

(Note that there are many possible witnesses for any given prime, but the rest of the certificate is unique up to reordering.)

31 -> {31, 3, {2, {3, 2, {2}}, {5, 2, {2}}}}
127 -> {127, 3, {2, {3, 2, {2}}, {7, 3, {2, {3, 2, {2}}}}}}
229 -> {229, 6, {2, {3, 2, {2}}, {19, 2, {2, {3, 2, {2}}}}}}
1093 -> {1093, 5, {2, {3, 2, {2}}, {7, 3, {2, {3, 2, {2}}}}, {13, 2, {2, {3, 2, {2}}}}}}
65537 -> {65537, 3, {2}}

(All the above outputs are examples of truthy inputs for the Pratt-certificate checking code.)

Example falsy inputs for Pratt-certificate checking

{31, 2, {2, {3, 2, {2}}, {5, 2, {2}}}}
{31, 3, {2, {3, 2, {2}}}
{31, 3, {2, {3, 2, {2}}, {5, 2, {2, {3, 2, {2}}}}}}
{127, 2, {2, {3, 2, {2}}, {5, 2, {2}}}}
{85, 4, {6, 5, {5, 2, {2}}}, {14, 3, {13, 2, {2, {3, 2, {2}}}}}}
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1
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Median fractals

I define 'Median fractal' as this.

Median fractal L1 is a equilateral triangle.

for median fractal Ln, Draw Ln-1, then for each triangle, draw all 3 medians in the triangle.

You will be given an integer n, draw Ln.


Sandbox

Any suggestions, guys?

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  • \$\begingroup\$ Would benefit from 1. A definition of the median of a vertex; 2. Diagrams of L_2 and L_3; 3. A better name. It's a variant on triangle centre fractals, but perhaps would be best called the vertex-median fractal. \$\endgroup\$ – Peter Taylor Apr 15 '17 at 12:12
  • \$\begingroup\$ I'm not sure what exactly "draw all 3 medians in the triangle" means. I think providing images of the first few fractals would help a lot to make the construction better understandable. \$\endgroup\$ – Laikoni Apr 17 '17 at 7:42
  • \$\begingroup\$ Should add: graphical output questions should at the very least specify minimum sizes to avoid trivial answers which give a 1x1 pixel bitmap output - although I suspect answers will favour vector graphics formats. \$\endgroup\$ – Peter Taylor Apr 18 '17 at 16:24
1
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These would be separate questions, and each would link to the other.

Cops: Make a bad password policy

Over the years, people have come up with some pretty bad password policies. Your challenge is to make such a policy, and to make a program that takes advantage of the weakness of this policy to brute force passwords written in it (a "crack"). For details on what constitutes a "crack", see the robber thread [link]. It should restrict the user to as small a selection of passwords as possible. Robbers will attempt to find cracks for your policy. If your answer is uncracked after 7 days, you make mark it safe by posting your crack. The "worst" uncracked policy (that is, the one that allows the fewest passwords) wins.

A "policy" is defined as a list of well-defined restrictions ("rules") on valid passwords. Here is an example:

  • Passwords must contain only digits, letters, and the characters '*&^'.
  • Passwords must be at most 8 characters long.
  • Passwords must not contain dictionary words (if you use this one, you must use a freely and programmatically accessible dictionary and tell us where to find it).

Policies:

  • must contain no more than 10 rules,
  • may not involve encryption of any kind, and
  • must be clear and unambiguous

For example, these would be a bad rules:

  • The MD5 hash or zipfile of the password must not contain the letter "a". (Uses encryption of a sort)
  • Passwords may not contain special characters. (It's unclear what counts as a special character)

Your answer must contain both the policy and the number of passwords it allows.

Robbers: Crack the bad password policy

Over the years, people have come up with some pretty bad password policies. Your challenge is to crack such a policy. These can be found in the cops thread [link]. To crack a policy, write a program to brute force passwords that adhere to that policy. Your program must run in linear time on the number of possible passwords allowed by the policy. You may do this by enumerating or iterating over all possible passwords in some way, such as by calling a function (called, for example, guessPassword) for each possible password. One option is to simply hardcode the possible passwords, if there are only a few. Here is an example (JavaScript):

function* getPasswords() {
    yield* ['a', 'b', 'c'];
}

Or, using the second approach:

function bruteForce() {
    for (let pw of ['a', 'b', 'c']) {
        if (guessPassword(pw)) {
            return pw;
        }
    }
}

Whoever cracks the most policies wins.


Sandbox

  • Is the linear time approach good? My original thought was just "your program must halt in a reasonable time", but that seems too vague, and this allows a person to crack even policies with a lot of possible passwords (though those hopefully wouldn't win anyway).
  • I could also just say, "pick a password in your policy and robbers will try to crack it", maybe having the cops supply a hash of the password.
\$\endgroup\$
  • 1
    \$\begingroup\$ I'm worried that this sort of challenge needs far too many arbitrary-seeming restrictions on the policy to make it work. The restriction against prime numbers is already fairly arbitrary, for example. Additionally, "linear time" doesn't make sense here; there's a finite number of possible passwords (according to the victory condition), meaning that any program that enumerates them runs in O(1) (thus faster than linear) by definition. Also, I think it's fairly easy to encode an NP-complete problem into the challenge in an understandable way; many are pretty intuitive. \$\endgroup\$ – user62131 Apr 17 '17 at 9:30
  • \$\begingroup\$ @ais523 Okay, if I require cops to have valid cracks, a few of those restrictions go away, since we don't have to worry about people making policies that are impossible to crack. Also, I know the programs would technically all be constant time, but I'm not sure how else to specify what constitutes a "fast" crack. I could just say, "must run in a few minutes on my machine" or something. \$\endgroup\$ – Brian McCutchon Apr 17 '17 at 16:12
  • \$\begingroup\$ "I'm not sure how else to specify what constitutes a "fast" crack" is IMO evidence that this idea is not workable. \$\endgroup\$ – Peter Taylor Apr 17 '17 at 17:57
1
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shortest angular path

Let's say you have a robot and you measure the orientation of a wheel (e.g. for tracking the exact distance), but the sensor just returns an angle between -180° and 180°. Then you have the problem that even if the wheel just moved three degrees from 179° to 182° the sensor will tell you that the wheel made a jump from 179° to -178°. This makes analyzing and interpreting the data a little bit cumbersome. Given a list of subsequent measurements your goal is now "smoothing" them out, such that from each entry A to the next B, in the list ([...,A,B,...]) there is at most a 180° jump.

Details

  • You can also assume other (single number) representations of angles, e.g. radians (0 to 2*pi) or gradian (0 to 400) or number of turns (0 to 1).
  • If it is more convenient, you can assume that the sensor will return data in [0°,360°] instead of [-180°,180°].
  • Which way you go if the jump is exactly 180° (or -180° or 540° etc.) is up to you.

Examples

[0 10 90 80 180 -130 -90 -120 -143 170 0] (Input)
[0 10 90 80 180 230 270 240 217 170 0]    (Output)
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1
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Smooth an array

A typical signal processing operation consists in smoothing a signal to reduce noise.

A very basic way to perform such smoothing, on an array of integers, is using the following formula:

enter image description here

where y'_t is the smoothed value at index t, y_t is the original value at index t, and where β is a smoothing parameter (in [0,1]). Note that y' = floor(y + 0.5) is the classic round half up operation.

For t = 0, there is no y'_(t-1), thus we set that y'_0 = y_0.

Applying that operation on a sequence of integers pictured below on the left, produces the sequence of integers pictured below on the right:

enter image description here

Challenge

Given a list of integers and β, output that list of integers smoothed in that way.

All integers of the list will be guaranteed to be in the interval [1, sup) where sup is the maximum integer representable in the integer type you use in your language. All integers of the input must be taken, and all integers of the output must be printed, in the decimal base (unless your language does not support decimal numbers, in which case you may use the standard base your language uses).

The input list is guaranteed to have at least 2 elements. You may take that input list in any way or format that is sensible in your language.

β is guaranteed to be in [0,1].

Test cases

TODO add more

List                               β     Output
[1,2,7,3,11,13,26,5,18,4,3,2,1]    0.5   [1,2,5,4,8,11,19,12,15,10,7,5,3]

Scoring

This is , so the shortest answer in bytes wins.

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1
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Output the Name of a Number

Idea from a recent question on math SE.


Write a program or a function that takes an integer from range 0 to 255 (inclusive) and outputs the name of its unsigned 8-bit binary representation. Input can be in any integer format you like, but the outputted name must match the number's unsigned 8-bit representation.

The name of the number is determined by the positions of its binary digits that are 1:

1 − John
10 − Watson
11 − Watson John
100 − Kevin
101 − Kevin John
110 − Kevin Watson
111 − Kevin Watson John

Let the names for the eight bits be Laura, William, James, Mary, Alice, Kevin, Watson, and John.

So now the name of 255 (11111111 in binary) is:

Laura William James Mary Alice Kevin Watson John

Zero doesn't have a name under this system so you may output an empty string or nothing at all. Trailing whitespace is allowed for all outputs.

Test cases:

<input (as decimal)>
<8-bit binary>
<output>

10
00001010
Alice Watson

42
00101010
James Alice Watson

128
10000000
Laura

189
10111101
Laura James Mary Alice Kevin John

55
00110111
James Mary Kevin Watson John

96
01100000
William James

37
00100101
James Kevin John

0
00000000


255
11111111
Laura William James Mary Alice Kevin Watson John

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

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1
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Optimize for the Test Cases

Given a set of test cases (pairs of input and output strings) as input, output a program in a programming language of your choice that consistently and deterministically produces the correct output for each input.

Rules

  • You may choose any programming language for the output programs, so long as it is a programming language by our definition, it existed prior to the creation of this challenge, and it is capable of taking arbitrary ASCII strings as input and producing arbitrary ASCII strings as output.
  • Your solution must use the same programming language for all inputs. The output programs do not need to be in the same language as the solution.
  • The output program must consistently and deterministically produce the correct output for each input. That means that, no matter how many times the program is run, it will always produce the correct output (barring any uncontrollable accidents like cosmic rays twiddling bits). PRNGs are allowed so long as a constant seed is provided (making the output consistent and deterministic).
  • The test cases' inputs are provided without quotes, but you may require that the input be quoted if it is necessary or convenient (as per our usual policy on quoted input). However, you must either always or never have quotes on the input - you can't have some with quotes and some without.
  • It does not matter what the output program does for inputs that are not part of the specific test case the program was created for.
  • You may optionally take the number of test cases as input, if that is convenient or necessary.
  • Every input in a set of test cases will be mapped to a unique output. Input values will not be repeated within a set of test cases (so [(3, 5), (3, 6)] wouldn't be a valid test case).

Scoring

Your score will be equal to the sum of the byte counts of all generated programs for the set of scoring cases. Lowest score wins. This is a competition within output languages, not a competition between output languages, so don't be afraid to choose a language that is more verbose than others. I reserve the right to change the scoring cases should it be necessary.

Examples

A C++ program that outputs (poorly-golfed) Python functions:

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

const string function_skeleton_start = "lambda s:{";
const string function_skeleton_end = "}[s]";

int main() {
    int N = 0;
    string in, out;
    stringstream program;
    program << function_skeleton_start;
    cin >> N;
    cin.ignore();
    for(int i = 0; i < N; ++i) {
        getline(cin, in);
        getline(cin, out);
        program << "'" << in << "':'" << out << "',";
    }
    program << function_skeleton_end;
    cout << program.str() << endl;
    return 0;
}

An example input:

2
foo
bar
bar
foo

The corresponding output:

lambda s:{'foo':'bar','bar':'foo',}[s]

Test Cases

(TBD)

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  • \$\begingroup\$ I'd be very interested to see some of the answers this challenge would get +1 \$\endgroup\$ – MD XF May 10 '17 at 1:21
1
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Output "Hello, World!"... Even before it runs?

Please note that this challenge only applies to languages that have a build stage and a build log.

Output "Hello, World!" to the build log. The program may or may not be compiled successfully, the job is to just output "Hello, World!" somewhere in the build log.

Example (C/C++)

#pragma message("Hello, World!")
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  • 1
    \$\begingroup\$ could it be more interesting as a rosetta-stone challenge? \$\endgroup\$ – John Dvorak May 13 '17 at 9:32
1
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Output the Balmer Series

Challenge

Write a program which outputs the following image (note, it is an svg):

It is the emission spectrum of hydrogen, caused by the Balmer series: https://en.wikipedia.org/wiki/Hydrogen_spectral_series#5

Your program must not read the image from the internet or a local file.

The image may be to an image file or a graphics window. If not a vector, the image sides must be greater than 400 pixels.

Your image must have the same colours and same ratios of spacing between each line.

Winning

Shortest code wins.

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  • \$\begingroup\$ What does it mean to output the image "exactly"? It's obviously not pixel-for-pixel for two reasons: firstly, because the image isn't raster, and secondly, because the spec allows for variation in image size. \$\endgroup\$ – Peter Taylor May 12 '17 at 22:22
1
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Extension of MIME-Type

Your task, given this list of extension and MIME-types, is to choose exactly 20 of them and create a program that takes in either e, the extension, or m, the MIME-Type, and outputs its counterpart.


Example (if my set was [.pdf, .doc]):

Cases to handle:

f('.pdf') = application/pdf
f('application/pdf') = .pdf
f('application/msword') = .doc
f('.doc') = application/msword

Cases you don't have to touch:

f('Nonsense') = [Error, null, false, whatever]

I & O

  • Input will be a single string, so will output.
  • You must handle 20 mime-type combinations and mention which ones you are handling.
  • Trailing spaces and newlines are fine.
  • Extensions always include the preceding period.
  • When choosing a long extension like .cryptocode, if you return the MIME-type of .cryptocode for an input of .cry it will be considered an invalid submission, remember this.

Winning

\$\endgroup\$
  • 3
    \$\begingroup\$ kolmogorolofvlfoao-complexity??? \$\endgroup\$ – programmer5000 May 17 '17 at 0:06
  • \$\begingroup\$ Could you add a pastebin with the list in this format: .123<tab>application/vnd.lotus-1-2-3<newline>.3dml<tab>text/vnd.in3d.3dml to make reading easier? \$\endgroup\$ – programmer5000 May 17 '17 at 0:09
  • \$\begingroup\$ Be sure to include the list in the question itself when you post this on main. We want questions to be self-contained. \$\endgroup\$ – John Dvorak May 17 '17 at 3:53
  • 2
    \$\begingroup\$ "When choosing a long extension like .cryptocode, if you return the MIME-type of .cryptocode for an input of .cry it will be considered an invalid submission, remember this." - why? Do I have to detect if the input is one of my set? This will reduce my compression ratio significantly. \$\endgroup\$ – John Dvorak May 17 '17 at 3:56
  • \$\begingroup\$ @JanDvorak it's too big for posting here, and if pastebin goes does a lot of the internet would lose a lot of data. \$\endgroup\$ – Magic Octopus Urn May 25 '17 at 17:04
  • \$\begingroup\$ @programmer5000 you can post it if you want. \$\endgroup\$ – Magic Octopus Urn Aug 27 '17 at 2:59
  • \$\begingroup\$ Concerning the "exactly 20" requirement: Are we allowed to output anything we want if fed something not in that 20 or does it need to output a falsey value? The addition of the word "whatever" added confusion for me. \$\endgroup\$ – Engineer Toast Mar 13 '18 at 14:22
  • \$\begingroup\$ @programmer5000 Tab-separated version for OP's benefit. \$\endgroup\$ – Engineer Toast Mar 13 '18 at 14:31
1
\$\begingroup\$

Is it a number?


Given an input, output truthy if it is a valid floating point number, and falsy if it is not. The format that is used in this challenge is [-][<integer>][.][<integer>][e[-]<integer>], where square brackets specify optional values. At least one group in the first section ("mantissa") needs to exist.

Here are some examples of inputs:

Valid

100
-100
10.245
-12.44
.5
-.2
0.3
-0.776
3365883.0000112
5e3         # equal to 5000
-.5245e3    # equal to -524.5
155.0e-3    # equal to 0.155
-5e-1       # equal to -0.5
.           # equal to 0.0

Invalid

feed me numbers
-5-3
5..2
4160e
e4
543tomatoes234
123 456
-3e0.15
4q2

Rules

  • Standard loopholes apply
  • This is a , shortest answer wins. However, it will not be accepted.

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  • \$\begingroup\$ For reference, -?\d*(\d+|\.\d*)(e-?\d+)? will match it if it's a number; it will match parts though so beware of that. \$\endgroup\$ – user42649 May 17 '17 at 4:15
  • \$\begingroup\$ How to handle empty input, and is -0 valid? \$\endgroup\$ – Pavel May 17 '17 at 4:19
  • \$\begingroup\$ @Phoenix Empty input is invalid. -0 is valid for this challenge. \$\endgroup\$ – dkudriavtsev May 17 '17 at 4:19
  • \$\begingroup\$ Please add those as test cases. \$\endgroup\$ – Pavel May 17 '17 at 4:57
  • 1
    \$\begingroup\$ Also, -, e, .e4, -e4, -. \$\endgroup\$ – Pavel May 17 '17 at 4:58
  • 1
    \$\begingroup\$ This has definitely been done before here \$\endgroup\$ – caird coinheringaahing May 17 '17 at 6:55
  • 1
    \$\begingroup\$ How is . equal to 0.0? Will the valid inputs be as integers, strings or either? \$\endgroup\$ – Shaggy May 17 '17 at 12:33
  • \$\begingroup\$ @Shaggy This is meant to represent floating point literals. Valid inputs are strings. \$\endgroup\$ – dkudriavtsev May 17 '17 at 21:12
1
\$\begingroup\$

Don't break the bridges!

Introduction:

You are a worker, who is in charge of managing a set of bridges, connecting a square grid of "nodes":

N - N - N
|   |   |
N - N - N
|   |   |
N - N - N

(the grid here is 3 by 3, but they can be larger).

Each of the bridges has a set capacity from 1 to 10, and each of the bridges has a number of cars over them, also from 1 to 10.

  • If a bridge has a higher capacity than the number of cars on that bridge, then it is considered "safe", and you can cross over it.
  • If a bridge's capacity and number of cars going over it are equal, then it is considered "stable". It won't collapse, but you can't cross over it.
  • If a bridge has a lower capacity than the number of cars on that bridge, then it is considered "collapsing", and you only have a limited amount of time to fix it.

When a bridge has n capacity and m cars, with n smaller than m, the time it takes to collapse is:

      m + n
ceil( ----- )
      m - n

You must take materials (and therefore reduce the bridge's capacity) from other bridges and arrive to those bridges on time to fix them! To get materials from a bridge, you must cross over it. For example, take this small arrangement:

A - B

The bridge between A and B (which we'll call AB) has 3 capacity, and let's say you're on A, and want to take 1 material. To take the material, simply cross from A to B.

Now, AB has 2 capacity, and you have 1 material on you. You may only cross over bridges that are "safe", though (or if you're fixing a bridge, which is explained in the next paragraph).

To fix a bridge, you must go over it, thereby depositing all materials needed to fix the bridge. For example, in the example above, if AB had 1 capacity and 2 cars currently on it, and you had 2 material on you, once you cross the bridge you will have 1 material, because that is all that's required to fix the bridge.

You must fully cross a broken bridge before the bridge collapses, otherwise it will break. Each crossing of a bridge takes 1 hour, and the time it takes for the bridge to collapse is shown in the formula above. For example:

A
|
B
|
C - D

In this example, if your starting node was A, and CD only had a "lifespan" of 2 hours, the bridge would collapse before you can get to it (crossing AB takes 1 hour, crossing BC takes another hour).

Task:

Your task is to make a program that calculates, given a list of bridges, which are represented themselves as lists of two elements (first element is capacity, second element is cars on the bridge), whether or not it's possible to fix all of the bridges. The bridges work from top-to-bottom, left-to-right - so an input of

[[3 2] [3 2] [2 5] [5 1]]

means that the actual grid looks like this:

    3
 A --- B
 |  2  |
3|2   2|5
 |  5  |
 C --- D
    1

So AB has a capacity of 3 and 2 cars, AC has a capacity of 3 and 2 cars, BD has a capacity of 2 and 5 cars, and CD has a capacity of 5 and 1 car.

Rules / Specs:

  • Your program must work for, at least, 10 * 10 grids.
  • Your program may accept the input as either a string with any delimiter, or a list of lists (see example I/O).
  • Your program must output the same value for true for all true values, and it must output the same value for false for all false values.
  • You can either submit a full program or a function.

Example I/O:

[[5 5] [5 5] [1 1] [3 3]] => true
[[2 5] [2 2] [3 3] [1 2]] => false
[[3 2] [3 2] [2 5] [5 1]] => true

NOTE, you can take the input like this as well:
[[3, 2], [3, 2], [2, 5], [5, 1]] (Python arrays)
3,2,3,2,2,5,5,1                  (Comma-separated string)
3 2 3 2 2 5 5 1                  (Space-separated string)
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  • \$\begingroup\$ "You may only cross over bridges that are "safe", though. To fix a bridge, you must go over it". Huh? \$\endgroup\$ – Peter Taylor May 20 '17 at 10:53
  • \$\begingroup\$ @PeterTaylor Fixed. \$\endgroup\$ – clismique May 20 '17 at 11:02
  • \$\begingroup\$ Will the input always have a square number of elements? \$\endgroup\$ – ETHproductions May 20 '17 at 11:38
  • \$\begingroup\$ @ETHproductions The nodes are square, but the input won't always have a square number of elements, because the number of paths diverges from the number of nodes (4 for 2 * 2, 12 for 3 * 3, etc.). I'm all ears to better input formats, I understand this one would be hard to process. \$\endgroup\$ – clismique May 20 '17 at 11:40
  • \$\begingroup\$ Ah, so it'll always be a number of the form 2*n*(n-1), or 4 times a triangular number. Not sure if there is any better input format... \$\endgroup\$ – ETHproductions May 20 '17 at 12:33
1
\$\begingroup\$

How many times?

Inspired by Rotational symmetry of string.

Given a string, return its shortest substring that, when repeated a number of times, will produce the original string, as well as the number itself.

Test cases:

"ABCDABCDABCDABCD" => "ABCD", 4
"AAAAAAAAAA" => "A", 10
"ABCDEFGHIJKLMNOPQRSTUVWXYZ" => "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 1
"" => "", 0
"Don't repeat yourself. Don't repeat yourself. " => "Don't repeat yourself. ", 2

Rules:

  • You may return the substring and the number in any format you'd like, as long as it's consistent and clear i.e. you can always separate the number correctly from the substring e.g. abc12 isn't allowed since you can't determine whether abc is to be repeated 12 times or abc1 is to be repeated 2 times. The substring must be returned verbatim, while the number can be returned in any generally allowed format per meta consensus.
  • The substring must be the shortest possible.
  • For the empty string, you must return "" and 0.

Sandbox

  • Is the challenge description golfed enough? :P
  • May I improve the return/output format?
\$\endgroup\$
  • \$\begingroup\$ Pleas can you change the abc2 should be repeated 1 time to abc1 should be repeated 2 times? It makes more sense. \$\endgroup\$ – caird coinheringaahing May 20 '17 at 21:16
  • \$\begingroup\$ @RandomUser Typo; should be fixed. \$\endgroup\$ – Erik the Outgolfer May 20 '17 at 21:17
  • \$\begingroup\$ Related, supertask \$\endgroup\$ – Peter Taylor May 21 '17 at 7:02
  • \$\begingroup\$ What range of characters are possible within the string? Can newlines occur? \$\endgroup\$ – Steve Bennett May 21 '17 at 8:58
  • \$\begingroup\$ Also, why not just specify that the output format is "12\nabc"? Otherwise there may be arguments on everyone's answers about whether or not they meet the requirements. \$\endgroup\$ – Steve Bennett May 21 '17 at 8:59
  • \$\begingroup\$ @SteveBennett And that's what the second question in the "Sandbox" section is for. Please note that I do not intend to restrict the output format like this. \$\endgroup\$ – Erik the Outgolfer May 21 '17 at 11:47
1
\$\begingroup\$

Add a language to a quine


Add a language to a quine program. Your program must output itself in all languages used so far.

Second to last answer wins after no answers have been posted for two weeks.


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  • \$\begingroup\$ this is hard mode of existing challenge? \$\endgroup\$ – Destructible Lemon May 24 '17 at 3:58
  • \$\begingroup\$ @DestructibleLemon Basically. \$\endgroup\$ – dkudriavtsev May 24 '17 at 3:58
  • \$\begingroup\$ @Okx So that you can't win by posting an answer which is impossible to add onto. \$\endgroup\$ – ETHproductions May 25 '17 at 15:12
1
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Build a simple 2D game engine

Write a program that take input specifying specs of a simple 2D game regarding the following:

  • GUI: a space where you can print text
  • Scene: a 2D stage where player\enemy move
  • Input Scheme: a way to check for input
  • Player: one object
  • Enemy: one or more objects
  • Coin: one object
  • Engine: manage running scenes

The program should offer the following instructions:

  • generate: create an object & place it in the scene
  • destroy: destroy an object or hide it from the scene
  • move: move an object to a different location, or apply motion
  • collision: check if two objects are colliding or interlacing
  • write: write to GUI
  • param: create, modify, or read an integer
  • terminate: stop running update, and run end
  • a way to do an if-else

A Scene should at least have the following functions:

  • start: sequence of instructions, applied once when the scene is fired
  • update: sequence of instructions, applied N-times per second
  • end: sequence of instructions, applied once when the scene is terminated

Example

Input the game spec

GUI:1,10

SCENE:5,10

START: GEN(p1,PLAYER,5,1); GEN(e1,ENEMY,4,4); GEN(c1,COIN,3,6); PARAM(r1,0)

UPDATE:  IF(COLLISION(p1,c1), DESTROY(c1);PARAM(r1,PARAM(r1)+1));
         IF(COLLISION(p1,e1), DESTROY(p1);TERMINATE);
          IF(INPUT(ARROW-UP), MOVE(p1,-1,0));
        IF(INPUT(ARROW-DOWN), MOVE(p1,+1,0));
        IF(INPUT(ARROW-LEFT), MOVE(p1,0,-1));
       IF(INPUT(ARROW-RIGHT), MOVE(p1,0,+1));
       WRITE(g1,r1)

END: IF(PARAM(r1)=1, WRITE(g1,"YOU WON"), WRITE(g1,"GAME OVER"))

Output an interactive game

[ 0        ] <----- G:GUI (1 x 10)
+----------+
|          | <--- S:Scene (5 x 10)
|          |
|      C <-|----- C:Coin
|   E <----|----- E:Enemy
|P <-------|----- P:Player
+----------+
  • game starts with player, one enemy, one coin
  • you can control the player with arrow keys
  • if player come in contact with enemy, player disappear then it ends
  • if player come in contact with coin, coin disappear then it's counted
  • when game ends, if coin count is 1 you win, otherwise you lose

Meta

  • What tags to use?
  • How can I simplify the requirements so that it's possible to solve it with languages of simple means?
  • I haven't seen many challenges like this, to write a program which parse instructions to create an interactive program within it, what do you think?
\$\endgroup\$
1
\$\begingroup\$

Distinct strict partition counts


Related

The Task

Write a function or program that, given a positive integer n, returns or prints an array (or list, set, etc.) of length l such that each index i contains the count of distinct partitions of size i of n (one-indexed) and l is the maximum size of partitions for n.

Definition

Let f(n) implement the task described.

Consider f(10)

10 may be broken into the following distinct partitions:

10         // Size 1
9,1        // Size 2
8,2
7,3
6,4
7,2,1      // Size 3
6,3,1
5,4,1
5,3,2
4,3,2,1    // Size 4

There are:

  • 1 distinct partitions of size 1.
  • 4 distinct partitions of size 2.
  • 4 distinct partitions of size 3.
  • 1 distinct partitions of size 4.

Therefore, f(10) returns [1, 4, 4, 1].

Test Cases

TODO

\$\endgroup\$
  • \$\begingroup\$ A008289. \$\endgroup\$ – Peter Taylor May 24 '17 at 21:25
  • \$\begingroup\$ @PeterTaylor Thank you. I was dreading the larger test cases. \$\endgroup\$ – Addison Crump May 24 '17 at 21:35
  • \$\begingroup\$ in my opinion this suggestion is quite clearly defined and simple, I like it - but it didn't attract votes nor critique .. do people find it too mathematical? I was going to propose something similar related to enumerating Standard Young Tableaux given a partition shape \$\endgroup\$ – jayprich Aug 22 '18 at 10:14
1
\$\begingroup\$

Show key code

Inspired by the showkey command.

Task

You have to output the key and if is a key-up or a key-down event. I exemplify:

enter image description here

The output I want:

Key X Down
Key X Up

for both the instants you press or release a key.

You can output it on a console or on a GUI.

It is , so shorter code wins.

\$\endgroup\$
  • 1
    \$\begingroup\$ I don't think this is currently clear. What keys correspond to what key codes? You should include either a list, or some source where one can determine which keys correspond to which codes. \$\endgroup\$ – Wheat Wizard May 27 '17 at 0:18
  • \$\begingroup\$ @WheatWizard i think, there is standard. Also, if not, there will be keyboard/language-related key code table \$\endgroup\$ – Евгений Новиков Jul 31 '17 at 11:48
1
\$\begingroup\$

Set The Shapes

Updated on 23/05/17 with new shapes & questions

Challenge

Let s be the sequence of polygonal numbers with S sides and t be the sequence of polygonal numbers with T sides. Take the set union of the first n elements of s and the first n elements of t.

Input

3 integers, n, s & t where:

  • n>0, 2<(s,t)<13 and s!=t
  • The values of s & t each represent a different polygonal number type:
  3 = Triangle
  4 = Square
  5 = Pentagon
  6 = Hexagon
  7 = Heptagon
  8 = Octagon
  9 = Nonagon
 10 = Decagon
 11 = Hendecagon
 12 = Dodecagon

Output

An array of the set union of the first n numbers of shapes s and t in ascending order.

Example

(assuming 0-based indexing)

  • Input: n=5, s=3, t=4
  • The first 5 triangular numbers are 0, 1, 3, 6, 10
  • The first 5 square numbers are 0, 1, 4, 9, 16
  • Output: [0, 1, 3, 4, 6, 9, 10, 16]

Rules

  • Input must be 3 separate integers
  • Output must be an array (or equivalent in your chosen language)
  • If your chosen language isn't capable of handling either or both of the above then standard I/O methods apply
  • s & t are guaranteed to be different but you must be able to handle them being input in either order - smallest first or largest first
  • This is so lowest byte count wins

Test Cases

Input: 5, 3, 4
0-Based Output: [0, 1, 3, 4, 6, 9, 10, 16, 20]
1-Based Output: [1, 3, 4, 6, 9, 10, 15, 16, 25]

Input: 10, 9, 8
0-Based Output: [0, 1, 8, 9, 21, 24, 40, 46, 65, 75, 96, 111, 133, 154, 176, 204, 225, 261]
1-Based Output: [1, 8, 9, 21, 24, 40, 46, 65, 75, 96, 111, 133, 154, 176, 204, 225, 261, 280, 325]

Input: 1, 7, 6
0-Based Output: [0]
1-Based Output: [1]

Input: 8, 3, 3
Invalid input as both shapes are the same

Input: 0, 2, 17
Invalid input as n<1, s<3 and t>12

Bonus Idea 1

Brownie points if you want to increase the range for s & t and include some other polygons (e.g., star, dodecagon).

Bonus Idea 2

Alter the challenge to only require that solutions be able to handle 5(?) different shapes with a score reduction for each additional shape, up to a maximum of 10(?).


Questions

This is my first challenge (inspired, in part, by this) so all feedback very much welcome.

  • Should I add or remove any tags?
  • Is the above sufficiently different from this and this?
    (Votes: 2 for this not being a dupe, 2 for it being a dupe of the second linked challenge)
  • Does everything read OK & make sense?
  • Should I include the formula for each shape in the question?
    I'm leaning towards "yes" as:
    1. For those that know them, figuring them out won't be a challenge
    2. For those that don't, figuring them out wouldn't add to the challenge
    3. As soon as one person posts a solution containing the formulas, that makes them available to everyone else anyway.
  • Should there be more (e.g., star, tridecagon+) or less possible shapes?
  • Would it improve the challenge if I allowed solutions to pick a smaller subset of 5(?) shapes to work with? How about if that subset had to be sequential (e.g., 3-7 or 5-9 but not 3,5-8)?
  • What test cases should I add?
  • Do the bonus ideas add to or detract from the challenge?
    Answered: Bonuses are generally bad.
  • Is there a better name I can give this challenge?
  • Should I be asking any other questions?!
\$\endgroup\$
  • \$\begingroup\$ Yeah if you want to make it bigger just add the polygons and require them. But right now it looks to be a big enough handful. \$\endgroup\$ – Christopher May 17 '17 at 10:14
  • 1
    \$\begingroup\$ The two linked challenges don't seem similar enough to make this a duplicate (to me). \$\endgroup\$ – trichoplax May 17 '17 at 10:18
  • 2
    \$\begingroup\$ 1. I don't find "the first n numbers of both shapes" very clear. In fact, I can't find a single English phrase which cleanly expresses the meaning I reverse engineered from the example. I think it takes a few sentences or a mathematical expression. 2. The example looks wrong: what happened to 15? 3. I disagree with trichoplax: IMO this is a duplicate of the second linked question. \$\endgroup\$ – Peter Taylor May 17 '17 at 10:51
  • \$\begingroup\$ Thanks for your comments, @PeterTaylor. 1. Could you suggest some wording for the intro to make it clearer? 2. Yep, I messed that up in an edit - it's fixed now. 3. Fair enough, that's one vote for it being a dupe and one vote against - I'll update to reflect that. \$\endgroup\$ – Shaggy May 17 '17 at 10:55
  • 2
    \$\begingroup\$ Let S be the sequence of polygonal numbers with s sides and T be the sequence of polygonal numbers with t sides. Take the set union of the first n elements of S and the first n elements of T. \$\endgroup\$ – Peter Taylor May 17 '17 at 11:16
  • \$\begingroup\$ Many thanks, @PeterTaylor; I've edited that in. \$\endgroup\$ – Shaggy May 17 '17 at 11:21
  • \$\begingroup\$ I agree with Peter - this is too close to the second linked challenge. \$\endgroup\$ – Mego May 29 '17 at 10:23
  • \$\begingroup\$ Thanks for the feedback, @Mego. That ties the vote; guess this stays in the sandbox a little longer, so. \$\endgroup\$ – Shaggy May 29 '17 at 10:28
1
\$\begingroup\$

Dodge your death!

Introduction

"Muhuhuhahahah!" The mad scientist laughs. "You're trapped in my own little game!"

In front of you is a deadly pit of snakes, while behind you is a bottomless chasm. There's no way out, you're stuck!

"Two steps in front of you is the snake pit, and two steps behind you is the chasm. But! Before you move, you MUST write down a sequence of steps, forwards and backwards, and give them to me. But! because I'm feeling a bit evil today, I can make you take, instead of every step, every nth step, where n is less than your sequence length!

Choose wisely, now."

What's the maximum number of steps you can take before your imminent death?

Task

The intro above is a twist on the Erdős discrepancy conjecture, which was recently proven true (if you want to understand more about this, go to this video, by James Grime - I "stole" the twist question off of him).

The answer to the intro is 11 steps, but I won't go too in-depth with a proof. The answer, if the distance between you and the two "dangers" were 3 steps, is 1160 steps, although that isn't validated properly yet.

Your task is to make a program that generates the longest sequence of steps you can for a larger x, where x is the number of steps between you and the two dangers. For the purposes of this challenge, + represents a step forward, and - represents a step back.

So, an output for an input 2 is:

+--+-++--++

Which works, no matter what n the mad scientist chooses. For our challenge, x = 5.

Rules:

  • Your entire program should fit into your answer. However, if it doesn't fit, please provide an additional Github repository, or something similar.
  • You may update both your answer and program, if you can get a better score via optimisation.
  • In your answer, you must have:
    • Your program, in its entirety
    • The amount of steps generated - this will be your final score.
      • You must also provide an online version of the sequence in a Pastebin, or something similar. This is so we can check your answer.
    • The time your final score was last updated, so I don't have to check your history
  • You may NOT hardcode sequences beforehand
  • Your program must work for all x (where x is the number of steps between you and the pit & chasm), but you only need to provide the score for x = 5.

The answer with the largest score wins!

Meta:

  • What tags should I put in?
  • What things should I fix / elaborate?
  • For the "link to text file containing sequence" thing, I'm worried that the files might eventually get really big, as answers are more and more sophisticated. Is there any way to counteract that?
\$\endgroup\$
  • 1
    \$\begingroup\$ 1. "Your task is to make a program that generates the longest sequence of steps possible for a larger x" doesn't actually seem to be true: later text implies that you want something that terminates in a reasonable time rather than something which finds the actual optimum. 2. "The accepted answer will be the answer with the highest score, a week after the challenge is posted" is something which we've been discouraging for about the past five years. 3. For n=3 isn't the maximum possible actually 1160? \$\endgroup\$ – Peter Taylor May 31 '17 at 11:52
  • \$\begingroup\$ @PeterTaylor I got confused with what you meant by 2 for a while... you mean that the answer shouldn't be determined in time at all, right? \$\endgroup\$ – clismique May 31 '17 at 12:04
  • \$\begingroup\$ Yes, exactly. Accept the best answer after a week if you want, but don't imply that there's a deadline to submit answers. \$\endgroup\$ – Peter Taylor May 31 '17 at 13:34
  • \$\begingroup\$ Very closely related. The rules aren't quite the same, but this may nonetheless be similar enough to be a duplicate. Also, "your program must fit into your answer" is a meaningless length restriction; these sequences are highly compressible, so there's no reason not to calculate the best possible answer for n=5, hardcode it, and still have length left for a feeble attempt at other lengths. \$\endgroup\$ – user62131 May 31 '17 at 21:47
  • \$\begingroup\$ @ais523 The maximum length for n = 5 is extremely high, though, if I'm not mistaken. That would certainly make it extremely difficult to compress, and even if it was compressed, there's a very high chance of being beaten by some other answer. Also, that challenge's primary goal is code-golf, whereas mine doesn't focus on code golf at all, rather, generating the longest sequence possible. I can make n higher if you want. \$\endgroup\$ – clismique Jun 1 '17 at 8:00
  • \$\begingroup\$ @ais523 I got rid of the "program must fit into your answer" thing. \$\endgroup\$ – clismique Jun 1 '17 at 8:20
  • \$\begingroup\$ You go back and forth between x being the input and n being the input (the number of steps). It'd be better to be consistent. Also, instead of saying your program generates the longest sequence of steps possible, which can't be done because we don't know how long that sequence is, you should instead say that it generates as long a sequence as you can, or something like that. \$\endgroup\$ – isaacg Jun 1 '17 at 9:40
  • \$\begingroup\$ @isaacg Fixed both issues! \$\endgroup\$ – clismique Jun 1 '17 at 11:24
1
\$\begingroup\$

Data Categorization with a Si(g)n

Background:

Machine learning is a very powerful tool for categorizing data. It can help find a function that splits some already known data so that unknown values can be predicted. Typically, this function should be simple so that it does not "overfit" the data. As it turns out, previous studies have found out that the simple function f(x) = sgn(sin(ax)) can split most data into two categories with only a single coefficient to adjust! This will definitely (not) prevent overfitting, and should (not) be used for every application of machine learning.

sgn(x) is the sign function of x. As Wikipedia says,

         / -1 if x<0,
sgn(x) = |  0 if x=0,
         \  1 if x>0.

Data overfitting demonstration

Input:

Two ordered sets/arrays/lists of integers {m1, m2, m3, ...} and {n1, n2, n3, ...}.

You can take input as 2 lines of input, an array with the two arrays m and n as its elements, or any other reasonable method of input.

Output:

A value of a such that sgn(sin(ax)) equals 1 when x = m1, m2, m3, ..., and -1 when x = n1, n2, n3, ...

If no such value of a exists, you can output any non-numerical value.

Test cases:

Example inputs will be in the form [[m1, m2, m3, ...], [n1, n2, n3, ...]]
Input                  | Output
[[1, 5],    [2, 3]]    | 1.75
[[2, 3, 6], [5]        | 4.5
[[1, 3, 5], [2, 4, 6]] | 3.1415925
[[1, 6],    [2, 3]]    | Random junk
[[2, 3, 4], [1]]       | <Anything non-numerical>
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  • 1
    \$\begingroup\$ Is there a way to determine whether it is possible to find such a value? If yes, could you please add that to the challenge, if no, then I think this challenge is impossible to solve. Other than that you should probably define what happens for sign if the argument is zero. Is it enough if it we get a solution for a finite precision implementation of sin (but there would actually be no solution)? \$\endgroup\$ – flawr May 30 '17 at 18:27
  • \$\begingroup\$ I guess with a fast enough oscillation, there should be a solution for any data set in which there are not two points of opposite categories with the same x value. \$\endgroup\$ – feersum May 31 '17 at 16:29
  • \$\begingroup\$ @flawr When I designed the challenge, I didn't know if there was a solution. But, that's what made it interesting. While actually making the test cases and verifying them, I found a good method of finding possible values, and also test it they exist. However, I thought that it was the analysis of the function that made the challenge interesting, and so I wanted people to find their own methods of finding an answer. I'll maybe add some bounds to where you need to check, but I don't want to just straight up give away a possible answer that everyone will copy. \$\endgroup\$ – K Zhang May 31 '17 at 21:07
  • \$\begingroup\$ @feersum I had previously thought that that was the case, but it turns out that some data sets do not have a solution. I put 2 of them in the test cases section. \$\endgroup\$ – K Zhang May 31 '17 at 21:20
  • \$\begingroup\$ "Two sets/arrays/lists of numbers": define numbers. All of the test cases use integers, but restricting it to integers vs permitting doubles makes a big difference. \$\endgroup\$ – Peter Taylor Jun 1 '17 at 11:20
  • \$\begingroup\$ @PeterTaylor I've restricted the inputs to be integers only \$\endgroup\$ – K Zhang Jun 1 '17 at 11:54
  • \$\begingroup\$ @feersum It is relatively easy to see that the last test case does not have a solution. \$\endgroup\$ – flawr Jun 1 '17 at 12:30

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