# 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

To post to the sandbox, scroll to the bottom of this page 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, 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
• Comments addressing specific points mentioned in the proposal
• 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!

# Serialize and Deserialize a Binary Tree!

A coding website, leetcode.com, has a method to serialize a binary tree.

Serialize means making a binary tree linear.

For example, we have:

[1,[[2],[3,4,5]]]

1
/ \
2   3
/ \
4   5


First, we fill the missing places with 0:

      1
/ \
/   \
/     \
2       3
/ \     / \
0   0   4   5


Then read out all the lines from top to bottom:

->      1
/ \
/   \
/     \
->  2       3
/ \     / \
-> 0   0   4   5

[1,2,3,0,0,4,5]


Let's look at another example:

   1
\
2
/
3


Fill the missing places with 0:

   1
/ \
0   2
/ \
3   0


Note that 0 cannot have any child.

Therefore, this tree is serialized as [1,0,2,3,0].

Your task is to write two programs/functions, one to serialize, one to deserialize.

## Specs

• They may share code.
• The binary tree will only contain positive integers.
• A node in the binary tree is represented by [name,left_child,right_child].
• You may not pre-fill the binary tree with 0s.
• [1,0,2,3,0,0,0] is invalid.
• Unlike the website given, [1,0,2,3] is invalid.

# Notes

## String covering

Given a target string and a list of fragment strings, determine whether the target string can be formed by concatenating fragments, allowing overlaps. Each fragment can be used any number of times.

Example:

cataract, [tar, car, tar, act, rat] -> True

cataract
cat
tar
act


Is this a dupe? It's hard to search for. Is it too similar to Imposters at the Zoo?

• May 22 '16 at 1:28
• This challenge differs from zoo due to the fact that you can't "hide" mismatching parts, so I think it's fine. Not sure if there are any other potential dupes though. (also, I don't think Leaky's "related"s are that related) May 22 '16 at 4:25
• Just to double check, does "Each fragment can be used any number of times." mean that cancan, [can] -> True? May 22 '16 at 6:45
• I see a typo: "cat" isn't in the list but "tar" is twice
– user46167
May 22 '16 at 20:18

# Primary Chances

Write a program that lists all possible outcomes for a general election with any number of candidates.

Rules:

• Your answer must output how many states each candidate won in any format.
• Candidates can have any name.
• This is , so standard loopholes are forbidden, and shortest code wins.

# Sort 2D points by Sierpiński curve order

[ WORK IN PROGRESS]

### Input

A collection of distinct 2D points in the range [0,1] X [0,1].

### Output

An ordered collection of the same 2D points, meeting the criteria for Sierpiński curve order.

# Sierpiński curve order

• The points are in the order that the Sierpiński curve would pass through them.
• The order is cyclic - it does not matter which point is first.
• The order may be clockwise or anticlockwise/counterclockwise, provided it is consistent.
• The point at the centre of the range, (0.5, 0.5), may fall into any triangular quarter of the range, provided it is in the correct order among other points in that quarter. Similarly for all other points where both coordinates have finite binary expansion.

Although the curve is infinitely long and fills the unit square, it is arranged in a convenient shape that allows ordering points by calculating only a finite number of iterations. For example, if there are 4 points, one in each triangular quarter of the square, then they can be ordered based only on this information as the curve fills one triangular quarter before moving on to the next so the exact position without that quarter is not relevant.

# Sandbox questions

• Should ambiguous points be allowed to fall in any direction, or should I impose that they always fall left rather than right and up rather than down? Or just insist that the solution choose a consistent direction rule?
• Can I assume that any three points that can be described by floating point variables can be ordered in a finite number of subdivisions? I'm pretty sure but welcome a counterexample.

# Find ALL Longest Common Substrings

Unlike "Longest Common Substring" algorithm which returns just one string, or the length of it. This algorithm returns a score after taking all separate longest common substrings into account.

This program returns the score of how similar one string is to another according to the following rules:

1. isolate only the longest (non-overlaping) matching substrings.
2. score every longest substring found with this formula: (substring.length / ((string1.length + string2.length) / 2)) * substring.length
3. sum the scores and return.

STEP 1 Example:

string1 = ABCD

string2 = ZBCA


Deconstructing string1: (list of substring in order)

ABCD

ABC

AB

A (also found in string2)

BCD

BC (also found in string2)

B (also found in string2 but ignored - part of a longer substring)

CD

C (also found in string2 but ignored - part of a longer substring)

D

Matches: A, BC


STEP 2 Example: (substring.length / ((string1.length + string2.length) / 2)) * substring.length

A: (1/((4+4)/2)) * 1 = .25

BC: (2/((4+4)/2)) * 2 = 1


Step 3 Example:

.25 + 1 = 1.25, Return 1.25


Here's an example of longer strings of variable length:

string1 = Approximate This

string2 = Appropriate That Thing

Matches: Appro, i, ate Th,  Thi

Appro: (5/((16+22)/2)) * 5 = 1.3157894736842105263157894736842

ate Th: (6/((16+22)/2)) * 6 = 1.8947368421052631578947368421053

i: (1/((16+22)/2)) * 1 = 0.05263157894736842105263157894737

Thi: (4/((16+22)/2)) * 4 = 0.47368421052631578947368421052632

Return: 4.1052631578947368421052631578948


# Fizzbuzz for tensorflow

Since I was a new and naive user, I posted this question. In one day it got over 25 upvotes but was shut down for being too broad. Clearly there is community interest -- so by the suggestion of @DrGreenEggsandHamDJ I'll try it again in the sandbox. I'd really like to see some of the answers here, so I appreciate any help you can give turning this question into a proper submission.

Original text copied below:

Inspired by the job-interview with Joel Grus, the goal of this challenge is to write a tensorflow (or other deep/machine learning) program that learns Fizzbuzz and correctly prints out the answers to the positive integers less than 1000.

You can assume there are files named train.csv and test.csv and each contain a sorted list of sequential integers and the fizzbuzz answer:

 ...
100, buzz
101, 101
102, fizz
103, 103
104, 104
105, buzz
...
150000, fizzbuzz


test.csv spans 1-1000 and train.csv spans 1001-150000.

## Rules

1. You must not hard-code the rules to Fizzbuzz anywhere in your program. The output must be from a machine learned representation that is learned while running the code.
2. You must utilize train.csv in the training set and check your output against test.csv. You cannot use test.csv during training.
3. You must get all outputs correct from test.csv (but as is case with deep-learning, we'll allow your code to fail this rule no more than 5% of the time).
4. You may use any language and any external module (eg. python/tensorflow) as long they explicitly perform some kind of learning. Reference both the language and the module in the title of your post.
5. This is a popularity contest, so the submission with the most votes after one week wins.
• What are the odds this will work well without an obscene number of iterations? A week doesn't seem like much time to test more than a single method or two. May 25 '16 at 2:58
• @geobits I'm not sure, but I can train a decent random forest model on Netflix predictions or a CNN to recognize basic images in about in hour. I figured the community would enjoy the challenge of a basic programming task in an unconventional manner. Surely fizzbuzz can't be that hard... May 25 '16 at 3:05
• Well, one problem that comes to mind immediately is that you need it to output valid code at all. So you're going to need to compile/run/whatever for every slight variation in the code. So then you need to figure out what building blocks you can give it to start with. A list of keywords to try, just random ascii, somewhere in between? That part in particular seems underspecified, but could make or break the odds of it working imo. May 25 '16 at 3:08
• I foresee arguments over where exactly the line falls for "hard-cod[ing] the rules to Fizzbuzz". May 25 '16 at 11:45
• Hmmm....if you come up with arbitrary rules of fizzbuzz (like different numbers, different amounts of numbers), that might work to prevent hardcoding. May 25 '16 at 14:24

# What can I build? code-golf

## The Rules

Today I have decided to make geometric shapes out of toothpicks and gumdrops! However, I have a limited supply, so you have to figure out what I can build. I will give you an input in the format m n, where m is toothpicks (edges) and n is gumdrops (vertices.) Your output should be, in any output format of your choice, all 3D geometric shapes such that the amount of edges=m and the amount of vertices=n. The list of 3D geometric shapes you will use is this: Gist

• You may NOT access the Internet.
• No builtins relating to geometry or solids
• This is code golf, so shortest code wins.
• For no solids and invalid input, output nothing

# Examples

In: 3 2 Out: <empty>
In: CodeGolf123 Out: <empty>
In: 12 6 Out (Bonus): {regular tetrahedron,unit equilateral square pyramid,unit equilateral triangular dipyramid,unit equilateral triangular prism,unit equilateral pentagonal pyramid,regular octahedron} Out (Regular): {regular octahedron} 

• The first 3 rules can be deleted, as they're ppcg defaults May 22 '16 at 20:03
• Not the first...
– user46167
May 22 '16 at 20:04
• I think this would work better with 1 solid with exactly n and m edges and sides. May 22 '16 at 20:29
• How about doing that, but having this as a bonus?
– user46167
May 22 '16 at 20:37
• 1. KISS. Ditch the stuff about the external file: the overhead to load it and the overhead generated by requiring it to be UTF-8 mean that no-one would want to use it anyway. 2. "No builtins" literally bans people from using any language. Specify what built-ins are banned. 3. Make the data available in a usable format: i.e. a text file hosted on gist.github.com or pastebin. 4. The bonus is a no-brainer: a 10% saving for changing two == to <=. Either make it compulsory or remove it entirely, because as it stands it's just complication. May 22 '16 at 22:38
• @petertaylor: I am currently on a phone so I can't put a gist...
– user46167
May 23 '16 at 10:42
• There are a lot of shapes in that gist. Some of them are specified in different formats. If they're all to be supported it would be nice to have a standard format to represent them. Also some of these shapes specify different edge lengths. Will the challenge assume all edges are length 1 or will you potentially need to break toothpicks and keep track of the remaining pieces?
– Poke
May 26 '16 at 21:02
• @Poke 1. Will fix 2. Irrelevant-- you have all sorts of toothpicks, some miniscule and others huge.
– user46167
May 26 '16 at 23:43

# Challenge

Write a program that will play music based on input.

# Input

When your program is run it will be given a small song. Each note in the song will have 3 components:

[octave][pitch][duration]


where octave is the octave for the note to be played in, pitch is the key of the note (a b c d e f g), and duration is the length of the note in milliseconds. For example, 4c1000 would be middle c played for one second. Notes in a song are separated by spaces. Flats and sharps are possible, and they go after the note like this: 5gb1000 (5th octave g flat) for flats and 5g#1000 (5th octave g sharp) for sharps.

# Output

Your program must produce sound based on the input. If one of the notes in the input is 3f500, your program must play f in the third octave for a half of a second.

# Other notes

• This is code golf, so shortest program in (insert period of time) wins.

• No functions, only full programs.

• The sound can be whatever you please.

• Here are the frequencies of notes in the 4th octave in hertz:

• 4c - 261.63
• 4c#/4db - 277.18
• 4d - 293.66
• 4d#/4eb - 311.13
• 4e - 329.63
• 4f - 349.23
• 4f#/4gb - 369.99
• 4g - 392.00
• 4g#/4ab - 415.30
• 4a - 440.00
• 4a#/4bb - 466.16
• 4b - 493.88
• A list of all frequencies is here.

# Sandbox

• Is the challenge objective clear?
• This challenge may be hard for some languages, is that a problem?
• Is this already a challenge?
• Any positive feedback is welcome.
• I think this could be improved by explaining what the frequencies are for the pitches at a given octave, and then explaining how an octave relates to that. That information is necessary to answer in any language which doesn't handle that itself, so I think it warrants being in the post rather than being behind a (potentially stale) link. In addition, you probably need to have some kind of leniency about frequency and duration, machines are not perfect after all. May 27 '16 at 14:35
• @FryAmTheEggman Thank you for your feedback, updated challenge. May 27 '16 at 14:54
• Yes, this is already a challenge. (And, curiously, the second sandbox proposal which is a variant on that challenge in just a week). May 28 '16 at 10:55

# Plan a special tournament

tags: [more tags required]

I host a special tournament with any number n >= 2 of participants.

Here is a list of plans of tournaments for n = 2 to 20:

 2: 1) DE-2c-1w
3: 1) RR-3c-1w
4: 1) DE-4c-1w
5: 1) RR-5c-2w 2) DE-2c-1w
6: 1) RR-6c-3w 2) RR-3c-1w
7: 1) RR-7c-3w 2) RR-3c-1w
8: 1) DE-8c-1w
9: 1) RR-9c-4w 2) DE-4c-1w
10: 1) RR-10c-5w 2) RR-5c-2w 3) DE-2c-1w
11: 1) RR-11c-5w 2) RR-5c-2w 3) DE-2c-1w
12: 1) RR-12c-6w 2) RR-6c-3w 3) RR-3c-1w
13: 1) RR-13c-6w 2) RR-6c-3w 3) RR-3c-1w
14: 1) RR-14c-7w 2) RR-7c-3w 3) RR-3c-1w
15: 1) RR-15c-7w 2) RR-7c-3w 3) RR-3c-1w
16: 1) DE-16c-1w
17: 1) RR-17c-8w 2) DE-8c-1w
18: 1) RR-18c-9w 2) RR-9c-4w 3) DE-4c-1w
19: 1) RR-19c-9w 2) RR-9c-4w 3) DE-4c-1w
20: 1) RR-20c-10w 2) RR-10c-5w 3) RR-5c-2w 4) DE-2c-1w


## Explanation of the plan

• The entire tournament enters the first round, which has c = n participants.
• For each round:
• If c is a power of 2, then this round will be a double elimination round, with 1 winner. After this round, the tournament ends.
• Else, this round will be a round robin round, with floor(c/2) winners that continue to the next round.
• If only one winner continues, the tournament ends.
• Else, let c be the number of winners, and start again from "For each round".

## The Challenge

Given n, return a plan of the special tournament with n participants.

This is a , so shortest code wins.

TODO: Reword the explanation clearly, write more content.

• How does a round robin with five people work, where you have two winners? Most round robins would have a bye, so you'd end up with three winners continuing on. (same for any odd number) Jun 4 '16 at 19:02

# Golf a 2d maze (Yes, a whole game)

Nowadays, I am interested in making games. especially mazes. In this golf round of code, You should make a maze game. You can do it with just preset mazes, but, if you make it randomly generate, I will be a-maze-d and will give you bonus points.(Huh. is that a pun?) So, Go on, Why don't you try right now?

DETAILS:

• Input W(Up), A(Left), S(Down), D(Right) until the player gets to the finish.
• Display the maze and the player each input.
• Move the player Up if the input is 'W', Down if 'S', Left if 'A', and Right if 'D'.
• The Character for the wall and the player is undefined. you choose.
• The Character for the wall, the player and the end square should be all different.

MAZE GENERATING:

• You should get the Width and height in the input.
• Not Necessary, but you can use Prim or Kruskal.
• Also you can use the method mentioned in here.
• The spec as is probably has too many ambiguities, e.g. 1) What counts as a "maze"? 2) If I was to golf this question right now, I'd put the exit next to the player and make it so that the only valid move is into the exit. That would save a ton of bytes since I only have to check one input. 3) If random generation is optional, it's almost certain that it won't be done (but if you do make it mandatory, then you would need to specify what random generation means) 4) Do we have to handle invalid input from the user? Jun 5 '16 at 6:50
• In order for this to fit as a challenge on this site, it needs to have a winning criterion. For example, code-golf (shortest code wins), or fastest-code. You can also use code-challenge if you define a score based on something else, but there must be some way of assigning a score to each solution so they can be put in order and encourage competition. Jun 6 '16 at 13:52
• I think this could be an interesting challenge, but it needs to be well defined before it will be ready. Jun 6 '16 at 13:57
• It is code-golf.
– user54200
Jun 6 '16 at 14:01

# Light black box: generate mirror processors

[ WORK IN PROGRESS - LOTS OF OUTSTANDING QUESTIONS ]

# Input

The list of black box output values for all black box input values from 0 to 255 (inclusive), in any reasonable format. Each value is also in the range 0 to 255.

# Output

A text representation of a rectangular grid showing the locations and orientations of mirrors that will generate the appropriate black box output for each black box input.

# Specification

• The input bits arrive from the left of the grid, in the top 8 squares, initially travelling right.
• The output bits depart from the right of the grid, in the top 8 squares, travelling right.
• For both black box input and black box output, the most significant bit is at the top.
• Bits move through the grid horizontally or vertically until they encounter a mirror or the edge of the grid.
• Bits that leave the edge of the grid are lost.
• A bit that would move onto a mirror at the next step instead changes direction by 90 degrees clockwise or anticlockwise according to the mirror type, and takes a step in that direction (a bit never stays on the same square).
• If two or more bits arrive on the same square at the same timestep, all of them annihilate. Two bits can still pass through each other if this does not involve sharing a square (traveling in opposite directions, being adjacent facing towards each other on one step, and adjacent facing away from each other on the next).

Note that because a bit changes direction just before reaching a mirror, there cannot generally be a mirror in an input or output square, as this would prevent the bit entering/leaving by that square. However, a grid taking advantage of input/output that has no requirement for a given bit by placing a mirror that blocks a given input or output square is still valid provided it gives the correct behaviour.

[ PENDING ]

# Scoring

The score for each input is the area of the resulting grid. The total score will be the sum of the scores for each of the test inputs.

# Sandbox questions

• Is this too similar to domino circuits? The photons leave no trail so they can cross over their own and each other's paths arbitrarily many times. Also a given mirror can affect arbitrarily many photons, and each an arbitrary number of times.
• Is this a duplicate of anything else?
• Should the score be just the area of the grid, or also include the time between input and output? The time will have to be the worst case over all inputs, as reading the input before then would give a false result in some cases.
• Should output bits have to arrive at the same time?
• Should the time from input to output be required to be constant over all inputs?
• There cannot be more output bits than input bits. Should test cases reflect this, or should a mechanism be introduced to make all patterns of output possible?
• Should the particles be referred to as "bits", "photons", or something else?
• Currently tie break is first posted. Should the number of mirrors be taken into account as a tie break first?
• Should the grid wrap? I initially thought not, but then I realised there would need to be an extra row above the I/O rows to allow mirrors to redirect onto the top output bit. It might be simpler to keep to having the I/O rows at the very top, and simply put redirecting mirrors in the bottom row. This would make it possible to redirect onto rows 0 and 7 with only 8 rows in total.
• I've chosen mirrors that change the bit's direction just before impact, rather than on impact. I liked the fact that this gives an asymmetry - reversing the direction will not reverse the route taken. This introduces the potential for sending a bit back along part of the same path without trivially sending it back to its origin. Is there any reason to stick to the symmetrical case instead?
• The other thought that occurred to me was to have the mirrors change direction too, flipping between the two possibilities at each impact.
• There are 256**256 possible ways to assign a value from 0 to 255 to each of 256 different inputs. This is far too large a space for hardcoding all solutions. However, this doesn't necessarily mean that the worst case grids will be huge. A lower bound on the worst case grid area is log(256**256,3), which is just over 1292 (since there are 3 possible states for each square). The maximal lower bound is likely to be far higher than that, but I have no idea how much higher. I'm likely to settle on a small enough space that code can be expected to deal with any input, but still a large enough space that hardcoding is impossible (I don't want to explicitly rule it out). (Here ** indicates exponentiation, as used in python.)
• Mirrors that split bits, and bits annihilate on collision with each other. This will allow for arbitrary input and output rather than being restricted by the initial number of bits. I'm considering a number of possible approaches:
1. One mirror type only: always splits a single bit into two bits in the two directions perpendicular to the current direction.
2. 4 mirror types - each having a dead direction. A bit arriving from that direction is destroyed. A bit arriving from any other direction is split into two bits, one for each remaining direction.
3. 4 mirror types - each having a dead direction. A bit is only split into two bits if the two perpendicular directions are not dead. Otherwise only one bit is produced, in the available perpendicular direction (or no bits if the bit approaches from the dead direction).
• Can bits be left in the grid that do not terminate? Can a solution specify that the output should be measured at a set time, even if some bits will later reach the output squares altering the result? Should the output only be measured once all activity has ceased - excluding the possibility of using a repeating cycle?

## Implement an HTTP Tunnel

I'm bored at work and stuck behind a draconian proxy.

They can take my other ports but they can never take my port 80 freedom!

Help me get all the internets!

This is a challenge.

## requirements

• a single web page that processes GET and POST data and produces output
• if GET m=start
• creates any files you feel are necessary (named pipes, scripts, what-have-you)
• forks a process which will create a tcp connection
• connects to host and port based on GET variables h and p
• these variables should be cleansed so as not to allow command injection
• if GET m=in
• write the raw POST data to your forked process's tcp connection
• if GET m=out
• get all data available from the forked process's tcp connection and write as response
• should always return right away (let's say, in less than 1 second)
• if GET m=stop
• kill your forked process
• clean up any files it has created

## Test data

my first instinct was to have this challenge be three separate pieces of code, a client which listens on a port locally and interacts with the web page, the web page itself, and a script which will be forked by the web page. your score would be the sum of all their byte counts. i decided to remove the last as the start process would likely have to create other files so why not have it create the script to run as well, and decided to remove the first option as well to make it nice and even.

is this a feasible challenge? i will add more explanations and test data soon i think. adding my own client would probably be helpful

• HTTP is stateless, so this is a fundamentally broken way of designing a tunnel over it. I can't remember the exact headers, but there are ways in HTTP/1.1 of reusing a single connection for multiple bidirectional data transfers, and that would be the correct way of doing it. Jun 7 '16 at 11:02
• That's why the "start" mode is going to have to fork another process to handle the actual connection. I have this working with my php script forking a nc process which reads and writes from named pipes. I'll post it later. Sure you could use Connection: keep-alive but that connection usually times out pretty quickly, you'd have to implement your own pings to keep it alive, and there's no guarantee how long it would stay alive for. Jun 7 '16 at 23:28

# Code Golfed Rosetta Code Code Golfer

(any others? maybe , and/or )

Browsing examples on the Rosetta Code site, I can't help but think that all the code is just so long-winded, inefficient and ...well, readable. Something needs to be done.

### Challenge

Choose a language, then write a function that takes the example source code, in the same language, for specific tasks on Rosetta Code and returns a golfed version of that code.

Winner is the person who can golf the example tasks the most. However, this is a code golf challenge so the length of your own source matters too.

### Rules

1. Write a function in your chosen language that takes a string as input and returns a string as output (or equivalent - reading/writing to stdio or file, etc is also ok)
2. Input is the source code implementation, in your chosen language, of the following three specific tasks as shown on Rosetta Code (your function runs three times, once for each):
3. Output is a code golfed version of the input with identical functionality (again in the same language)
4. If there is more than one implementation of a task for a specific language, you must use the first listed
5. If your chosen language doesn't have an implementation for one of the tasks, then you need to add it yourself (following the Rosetta Code rules - don't go messing up their site just to get a better score here)
6. With the exception of the rule above, you may not, in any way, modify the content or order of examples on Rosetta Code
7. You must leave the logical flow of the algorithm mostly intact (eg. you can't simply replace the J quick sort code with /:~)

### Scoring

Score for each individual task is calculated as the output character count as a percentage of the input character count. Implementation score for your own code is simply its character count. Total score for a submission is the sum of the three task scores, plus the implementation score.

Submission with the lowest score wins.

So, assuming your function is 100 chars long and running it against the test tasks gives you the output counts shown, your overall score would be calculated as follows:

 Task      | Input char count | Output char count | Score
-----------+------------------+-------------------+--------
Quicksort |            600   |            400    |  67%
Happy Nos |            400   |            200    |  50%
GCD       |            200   |            150    |  75%
--------------------------------------------------+--------
Implementation score:                            |  100
--------------------------------------------------+--------
Overall score:                                   |  292


## Things I'm not sure about...

Before I post this as a challenge, it would be good to get input on a few things:

• Will the "if your language doesn't have an implementation" rule cause problems, or can people be trusted to provide sensible implementations that follow the intent of Rosetta Code and don't simply artificially improve their score on the challenge? Is it better just to deny entries from languages which don't already have implementations?
• With scoring, obviously it's a balancing act, a really terse language will likely get a solid "implementation" score, but should be less able to improve the length of the examples, whereas a verbose language will be the opposite. So, the having too few "tasks" included in the challenge will benefit terse languages, and too many will benefit verbose languages. I want to find a middle ground, so does three tasks seem reasonable?
• Will someone just find an edge case language which has a really easily golf-able Rosetta example, that will make it unbeatable?
• In the given example score, if an empty program echos then it would be better. More worryingly, this seems to allow coding to the test cases. Are the programs required to do something sensible with inputs other than the three test cases? Jun 9 '16 at 9:42
• @PeterTaylor - re: an empty program, I agree, this absolutely creates a minimum bar to beat, but even the most rudimentary whitespace stripping javascript function: (s) => {return s.replace(/[\s]{2,}/g,"");}; results in a score of 263, so my example score sheet is more the problem. Jun 9 '16 at 11:09
• @PeterTaylor - Re: coding to the tests, yes this is a bigger problem... The obvious solution is to simply include more tasks, since that would force people to target more generic things, rather than each individual task, but as stated the more you add the more you'll reward verbose languages (I think?)... One possible work around could be just to double things (i.e. have six tasks and make your implementation score, your code length x 2). Jun 9 '16 at 11:11

# Golf a golf-scoring program! code-golf

Given a space delimited array of integers, find the smallest number. It's that simple.

[Meta] This may in fact be a duplicate. Please tell me if so.

• This is basically a dupe of any regular sorting question, isn't it? Particularly something like Sign that word. Jun 9 '16 at 12:52

# Distance between two words

You are given an input of two strings consisting entirely of letter characters. The "distance" between two such strings is the number of operations from the following list that it takes in order to transform one word into the other:

1. Adding a letter anywhere
2. Removing a letter anywhere
3. Changing a letter's case

Since your boss wants to avoid wear on the office keyboards as much as possible, you have to write a very short program to determine the distance between words so you can fix the typos.

• Jun 10 '16 at 13:56
• Almost a duplicate of Leaky Nun's link. The only difference is that the linked challenge allows for straight substitution, whereas here it's two operations (a deletion and an insertion). Jun 10 '16 at 13:59
• Thanks guys, I had a brief look for dupes but couldn't find anything. If I come up with a good twist I'll edit the OP otherwise I suppose this is dead. Jun 10 '16 at 13:59

# Cross Validated

(This challenge is almost complete, but something doesn't feel quite right)

Continuing the theme of using site names as challenges...

# Your task

Write a program or function that accepts a string, and prints out the location, size, and validity of each cross in the string.

## Definitions

• Valid Cross- A cross where all four spokes of the cross are equal in length. The size of the cross is the number of segments of each cross.

Valid, size 0:

+


Valid, size 3:

   |
|
|
---+---
|
|
|

• Invalid cross- A cross where one or more spoke is a different length. The size is the number of segments of the longest spoke.

Invalid, size 2:

 |
|
-+--
|


Invalid, size 6:

+------


# Rules

• Each input will have one or more crosses.
• The program should print out the location of the center of each cross. The location is zero-indexed and measured in characters/lines from the top left.
• The size and validity, as defined above, of each cross should be printed out.
• Each test case must pass without printing to STDERR.
• Crosses will not overlap
• Your program can take input via a string (with line breaks), an array of strings (each representing a line), or a 2d array of characters.
• This is so shortest program, in bytes, wins

# Test Cases

+ +-


(0,0) size 0, valid

(2,0) size 1, invalid

   |
|     |
|     |
---+---  |
|     |
|  ---+
|


(3,3) size 3, valid

(9,5) size 4, invalid

(empty test case)


(must not crash or print to STDERR)

## This question isn't fair.

I want you to tell me the chances of flipping an coin n times and ending up on tails.

Naturally this isn't a fair coin. In fact, it isn't even a standard unfair coin, where the chance of flipping tails is always p. This is a sticky coin, where the chance of the coin staying the same is p; the coin is fair at other times.

The coin starts off heads, so when n is 0 or p is 1 then the answer is always 0.

Your program or function should be capable of calculating the result to at least six significant digits.

This is , so the shortest program wins!

• What does "the coin is fair at other times" mean? Jun 16 '16 at 13:12
• @LeakyNun Sorry, I'm not sure what you're trying to ask there. A fair coin is one which is equally likely to produce heads or tails but there is no way of predicting which. This coin isn't always fair; a proportion of the time p it repeats the last result.
– Neil
Jun 16 '16 at 14:22
• You said that the chance of the coin staying the same is p. Then, isn't the chance of it being different 1-p? So, do you mean that 1-p = 50%? Jun 16 '16 at 14:25
• I think it means that the chance of the coin staying the same is p + (1-p)/2 and the chance of the coin changing is (1-p)/2. Jun 16 '16 at 14:37
• @LeakyNun Ah, sorry, the chance of it being sticky is p, and of being fair is ¬p.
– Neil
Jun 16 '16 at 15:24
• Meaning, that the chance of it being the same is p+(1-p)/2 and the chance of it being different is (1-p)/2. What a meaningful obfuscation. Jun 16 '16 at 18:42
• That means that the chance of it not changing is p + (1-p)/2 = (1+p)/2, and Sp3000's closed form needs changing to (1 - p^n)/2. It's still not exactly an interesting function to golf. Jun 16 '16 at 18:43
• I can see I should have described the coin of having a chance q of flipping, and you needed to calculate the probability of an odd number of flips in n trials.
– Neil
Jun 16 '16 at 18:53
• (Removed my previous comment because I misunderstood and thought the probabilities were p and 1-p for same/change, but ditto Peter's comment) Jun 16 '16 at 22:59

# "Optimize" a RegEx

### Introduction

Inspired by atrociously large regex's like

/[0-9A-Za-z!@#$%&*()_\-+={[}\]|\:;"'<,>.?\/\\~]+[0-9A-Za-z!@#$%&*()_\-+={[}\]|\:;"'<,>.?\/\\~]*/g


I propose a challenge to create a string representing an optimized and sorted regex from an input string of characters expected to be matched.

### Rules

• only printable ASCII characters with code points 32 - 127 need to be supported:
 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_abcdefghijklmnopqrstuvwxyz{|}~  The RegEx output string should: • Group 3 or more consecutive code points in the input string together like begin-end • Sort the characters and groups in order of ascending code point • Escape the literal character - to \- to differentiate it from a range The RegEx output string should not: • Escape the characters !$()*+./=?[\]^{|}
• Support any RegEx escape sequences like \w, \d or \s

### Examples

Input:
helloworld
Output:
dehlorw

Input:
fedcabXZYVWU
Output:
U-Za-f

Input:
q0p[|iOf(oc61TSr4dVwQ8m;%YDAPM*a/2j&h~u}
Output:
%&(*/-2468;ADMO-QSTVY[acdfh-jmo-ruw|-~


Just so people can see what the last one's pattern is, here are the ASCII indices:

37,38,40,42,47-50,52,54,56,59,65,68,77,79-81,83,84,86,89,91,96,97,99,100,102,104-106,109,111-114,117,119,124-126


### Spoiler Alert

Example implementation in JavaScript ES6:

f=s=>[...s] // spread string into array
.sort() // sort array by ASCII indices
.map(
c=>c.charCodeAt() // convert each one to ASCII index
).reduce( // reduce sorted indices
(p,c)=>(
~p[0][0]+c? // if last index is not one less than current index
p.unshift([c]): // then start new run with this index
p[0].unshift(c) // else continue existing run
,p
),
[[]] // start reduce with empty run
).map( // map array of runs
a=>(
(
a=a.map( // map each run
n=>( // convert index back to ASCII
c=String.fromCharCode(n),
c=='-'? // if '-'
'\-': // then escape it
c
)
),
a.length>2? // if run has more than 2 indices
[a[0],'-',a.pop()]: // keep only the begin and end
a // else keep whole run
).reverse().join // reverse and join run
)
).reverse().join // reverse and join array

• This question seems to be about optimising regex character classes, not full regexes. Is that correct? Jun 17 '16 at 19:46
• @FryAmTheEggman I suppose you could say that. That's a more wordy title though so I just kept it simple. Jun 17 '16 at 19:47
• I could understand not requiring any escaping on the grounds that it's a minor detail. I could understand requiring enough escaping to make this actually a useful tool. But it seems really odd to require escaping - but not ]. Jun 17 '16 at 22:07
• @PeterTaylor I decided to escape only the characters that are necessary to determine whether an execution is correct or not. If you have an alternate suggestion, please feel free. Jun 18 '16 at 1:53

## Exercise your kids

I want you to output the nth verse of this kid's exercise song:

Head, and shoulders, knees and toes, knees and toes,
Head, and shoulders, knees and toes, knees and toes
And eyes and ears and mouth and nose,
Head, and shoulders, knees and toes, knees and toes.

Each verse is the same as the previous except that all occurrences of one word is masked by replacing it with a dash (you can use a two-byte dash of your choice) wherever it appears in the verse. The words are replaced in order however the word "and" is never replaced, therefore the next verse should look like this:

—, and shoulders, knees and toes, knees and toes,
—, and shoulders, knees and toes, knees and toes
And eyes and ears and mouth and nose,
—, and shoulders, knees and toes, knees and toes.

Also, the last verse should look like this:

—, and —, — and —, — and —,
—, and —, — and —, — and —
And — and — and — and —,
—, and —, — and —, — and —.

Your answer should specify whether n will range from 0 to 8 or 1 to 9.

• Could you show us what the second verse would look like? Jun 21 '16 at 10:26
• Although it can be deduced from the numbers, I'd recommend changing "one word is masked" to "all occurrences of one word are masked" to be explicit. Jun 21 '16 at 10:32
• Is this a challenge involving Unicode as the main topic? If not, can we replace — (U+2014) by a simple hyphen - (U+002D)? Jun 21 '16 at 10:34
• @LeakyNun No, but you may replace it with a double hyphen, as that's still 2 bytes.
– Neil
Jun 21 '16 at 10:38
• Actually, it is 3 bytes. Jun 21 '16 at 11:05
• Something to note is that "and" is the only word in the verse that starts with the letter "a". That means something like \b(?!a)\w+ will have its first match be the word to replace each time. Also, I don't believe any of the words are prefixes/postfixes of each other, so once you have them you can blindly replace all occurrences of them. This isn't a problem or anything, I just wanted to make sure you knew in case you wanted it to be harder. Jun 21 '16 at 12:50
• codegolf.stackexchange.com/q/100153/34718 Nov 17 '16 at 15:27

# Calculate the Average Squared Error

Given a line y = mx + b and a set of n points (xi, yi), find the average square error between the given line and each set of points.

Your goal is to create a function or program that given the values m, b, and the set of points (xi, yi), outputs the average square error according to the formula above.

## Rules

• This is so the shortest solution wins.
• Builtins that compute this value are not allowed. This includes builtins that compute a result which is a scaled value of this.
• Floating-point inaccuracies will not be counted against you.

tba

## Index sum and strip my matrix

Given a matrix/2d array in your preferable language

Input:

• The matrix will always have an odd length
• The matrix will always be perfectly square
• The matrix values can be any integer in your language (positive or negative)

Example:

1  2  3  4  5  6  7
2  3  4  5  6  7  8
3  4  50 6  7  8  9
4  5  6 100 8  9  10
5  6  7  8 -9  10 11
6  7  8  9  10 11 12
7  8 900 10 11 12 0


Definitions:

• The "central number" is defined as the number that has the same amount of numbers to the left,right,up and down

In this case its middlemost 1000

• The "outer shell" is the collection of numbers which their x and y index is or 0 or the matrix size

1  2  3  4  5  6  7
2                 8
3                 9
4                 10
5                 11
6                 12
7  8 900 10 11 12 0


## Your task:

Add to the central number the sum of each row and column after multiplying the values in each by their 1-based index

A single row for example

4  5  6  7  8


for each number

number * index + number * index.....

4*1 + 5*2 + 6*3 + 7*4 + 8*5 => 100


example:

 2 -3 -9  4  7  1  5  => 61
-2  0 -2 -7 -7 -7 -4  => -141
6 -3 -2 -2 -3  2  1  => -10
8 -8  4  1 -8  2  0  => -20
-5  6  7 -1  8  4  8  => 144
1  5  7  8  7 -9 -5  => 10
7  7 -2  2 -7 -8  0  => -60
|
78 65 60 45 -15 -89 10   => 154
|
=> -16

• For all rows and columns you combine these values..
• Now you sum these too => 154-16 = 138
• You add that number to the "central number" and remove the "outer shell" of the matrix

 0 -2 -7 -7 -7     => -88
-3 -2 -2 -3  2     => -15
-8  4 1+138 -8  2  => 395
6  7 -1  8  4     => 69
5  7  8  7 -9     => 26

19 69 442 30 -26


do this untill you end up with a single number

-2 -2 -3     => -15
4  1060 -8  => 2100
7 -1  8     => 29

27 2115 5

• Add 2114+2147 to 1060
• Remove the "outer shell" and get 5321
• Now we have a single number left

this is the output!

test cases:

-6

-6


-7 -1  8
-4 -6  7
-3 -6  6

2


 6  7 -2  5  1
-2  6 -4 -2  3
-1 -4  0 -2 -7
0  1  4 -4  8
-8 -6 -5  0  2

-365


 8  3  5  6  6 -7  5
6  2  4 -2 -1  8  3
2  1 -5  3  8  2 -3
3 -1  0  7 -6  7 -5
0 -8 -4 -9 -4  2 -8
8 -9 -3  5  7  8  5
8 -1  4  5  1 -4  8

17611


-9 -7  2  1  1 -2  3 -7 -3  6  7  1  0
-7 -8 -9 -2  7 -2  5  4  7 -7  8 -9  8
-4  4 -1  0  1  5 -3  7  1 -2 -9  4  8
4  8  1 -1  0  7  4  6 -9  3 -9  3 -9
-6 -8 -4 -8 -9  2  1  1 -8  8  2  6 -4
-8 -5  1  1  2 -9  3  7  2  5 -6 -1  2
-8 -5 -7 -4 -9 -2  5  0  2 -4  2  0 -2
-3 -6 -3  2 -9  8  1 -5  5  0 -4 -1 -9
-9 -9 -8  0 -5 -7  1 -2  1 -4 -1  5  7
-6 -9  4 -2  8  7 -9 -5  3 -1  1  8  4
-6  6 -3 -4  3  5  6  8 -2  5 -1 -7 -9
-1  7 -9  4  6  7  6 -8  5  1  0 -3  0
-3 -2  5 -4  0  0  0 -1  7  4 -9 -4  2

-28473770

• yes, that is much better. hard when English is your 3rd language Jun 21 '16 at 18:02
• No worries, English is a pretty incomprehensible language no matter who is speaking it ;) Anyway, you identify the central number as "the zero", but the example you gave actually has two zeros. Perhaps change the array or change the wording to the "middlemost zero"? Jun 21 '16 at 18:07
• For the process to work I think you need the matrix to be square, but I don't see a statement of that anywhere. Jun 21 '16 at 20:26
• added that @FryAmTheEggman also changed Jun 22 '16 at 16:52

# White Water Rafting

This problem is about finding the best path through a bunch of rocks on a 5-column wide river, without crashing your raft. A river looks like this (* reprsents a rock):

. . . R .
. R . . .
R . . . .
. . R . .
R . . . .
. . . . R


Each row will contain exactly 1 rock, no more, no less. Your raft can start on any space without a rock.

You can't maneuver your raft too much, so as you travel down the river, there are only 3 next places you can go (x is the next space):

. . @ . .
. x x x .


If there is a rock in your way, you can't go there. Your raft can't fit through rocks that are diagonally adjacent to each other. You can't beach your raft either. Finally, you can't go anywhere that would result in you crashing your raft.

@ . . . .
R x . . .   <- Can't go on rock, can't go oob

R . . . .
. R @ . .
. . R X .   <- Can't go through diagonal rocks

. @ . R .
. R x . .   <- Can go through non-adjacent diagonals,
R . . . .      Can't go to dead end.


Because you don't have much space on the raft to write this code, shortest code wins.

## Test cases:

Input:

. R . . .
. R . . .
. . . R .
. . . R .
R . . . .

Output:

R x . . .
. R x . .
. x . R .
x . . R .
R x . . .

Input:

R . . . .
R . . . .
R . . . .
R . . . .
R . . . .

Output:

R x . . .
R x . . .
R x . . .
R x . . .
R x . . .

Input:

. R . . .
. R . . .
. R . . .
. R . . .
R . . . .

Output:

. R x . .
. R x . .
. R x . .
. R x . .
R x . . .

Input:

. . . . R
. . . R .
. . R . .
. R . . .
. . R . .

Output:

x . . . R
x . . R .
x . R . .
x R . . .
x . R . .

Input:

. . . . R
. . . R .
. . R . .
. R . . .
R . . . .

Output:

[nothing] or [empty/blank array/matrix]


## Notes:

• Input can be in array of indexes, array of truthy/falsey values, or any other input format most comfortable to your language.
• Output should indicate the left-most valid path.
• Output can be in array of indexes, array of truthy/falsey values, or any other input format most comfortable to your language.
• Output does not have to be in the same format as input.
• Output nothing/(empty/blank) (array/matrix) if there is no valid path
• Standard loopholes are forbidden by default.

This is my first challenge, so please let me know if I have left anything out or something is unclear.

Related problems

I couldn't find any dupe targets looking through , so I'll look again in and later.

• I don't have 10 minutes now to sort through all of the dupe targets to work out which one is the most similar, but I guarantee that there is something similar enough that this is a dupe. Jun 23 '16 at 9:55

# Cypher-o-mania!

The year is 19XX.

You are a spy of some distant country, and your job is to send messages across the globe.

Unfortunately, because, frankly, you suck at being a spy, you need a way to obfuscate your information, so that when the opposition catches you (which they will), they won't know what the heck is written.

How are you going to do this?

Your task is, using two inputs (the first input the encoding "cypher" and the second the message), encode the message.

This is how the encoding works:

• The message only consists of the lowercase letters and the numerals.
• Because there are 36 different characters in total, we will convert each individual letter of the message to "base 9" (a = 00, b = 01, c = 02... 8 = 37, 9 = 38). This will be called the FSO, or First-Stage Obfuscation.
• For example, the message hello1 would then be translated to 07 04 12 12 15 28.
• Each individual "bit" of the FSO is then stripped of its first part. This will be known as the SSO, or Second-Stage Obfuscation.
• The example 07 04 12 12 15 28 is then translated to 7 4 2 2 5 8.
• This is where the encoder comes in handy! The encoder will consist of a string of numbers 0 to 3 (e.g. 1212003).
• You then add to the start of each digit of the encoder to the corresponding digit of the SSO. This is now the TSO, or Third-Stage Obfuscation.
• The example 7 4 2 2 5 8 with the encoder 1212003 is then converted to 17 24 12 22 05 08.
• With a shorter encoder (say 121), this step will "wrap around", so 7 4 2 2 5 8 with the encoder 121 will end up with 17 24 12 12 25 18.
• We then change the TSO back into readable characters, using the same "base 9" method.
• The two examples 17 24 12 22 05 08 and 17 24 12 12 25 18 will be converted to QWLUEI and QWLLXR respectively.

So, in summary:

Encoder: 121

Message: hello1

hello1 => 07 04 12 12 15 28 => 7 4 2 2 5 8 => 17 24 12 12 25 18 => QWLLXR

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

# META

• This is really confusing, and I don't really know how to phrase the "how the encoding works" bit better. Can anyone help me phrase this better? I can offer clarification on certain things if needed.
• This is basically a mildly astandard and irreversible Vigenère cipher, so it's virtually a dupe of this question. (I would also say that it violates one of the key criteria for being a good question, which is to have a motivation. The backstory IMO isn't a motivation because it doesn't explain why anyone would want to implement or use what's really a supremely bad hash function). Jun 23 '16 at 13:36
• @PeterTaylor Yeah, IK. I need a lot of things to fix with this question (I was extremely tired at the time, couldn't think of a nice backstory). Also, a few things about the dupe: ONE, it's 5 years ago, so there's bound to be some new answers out there (if it's even a dupe in the first place), and TWO, how is it a dupe? Jun 24 '16 at 10:55
• It's the difference between for (i=0 to n-1) s[i] = handleWrapping(s[i] + k[i % klen]) and for (i=0 to n-1) s[i] = handleWrapping(s[i] % 9 + k[i % klen] * 9). As far as I'm concerned that's a very minor transformation. Jun 24 '16 at 11:03
• @PeterTaylor Yeah, I kinda understand now. Still some questions, though. ONE: What language is that? TWO: Is there any way I could improve on my explaining? Jun 24 '16 at 11:22
• 1. It's pseudocode, because I didn't want to faff around working out what escaping a less-than sign needs in comments. 2. I'm not quite sure what you're asking, but I would ditch this idea completely and try to find something more original. See e.g. meta.codegolf.stackexchange.com/q/1475/194 Jun 24 '16 at 11:49
• @PeterTaylor Yeah, I can see those, but most of those ideas have been taken already, and I kinda want to move away from numbers for a bit and play around a bit with strings and whatnot. Any suggestions? Jun 24 '16 at 12:36

# Regex golf: Match the Thu'um-s

## Introduction

Skyrim is a game made by Bethesda and came out in 2011. One of the objectives of the game is to collect every 27 shouts (or Thu'um-s). In this challenge, you need to match every shout and nothing else.

## Shouts

This is the list of the available shouts in the game:

Raan Mir Tah
Laas Yah Nir
Mid Vur Shaan
Feim Zii Gron
Gol Hah Dov
Od Ah Viing
Hun Kaal Zoor
Lok Vah Koor
Ven Gaar Nos
Zun Haal Viik
Faas Ru Maar
Mul Qah Diiv
Joor Zah Frul
Gaan Lah Haas
Su Grah Dun
Yol Toor Shul
Fo Krah Diin
Liz Slen Nus
Kaan Drem Ov
Krii Lun Aus
Rii Vaaz Zol
Tiid Klo Ul
Strun Bah Qo
Dur Neh Viir
Zul Mey Gut
Fus Ro Dah
Wuld Nah Kest


Additionally, every shout can have 3 levels depending on what the player collected so far, each level adds a new word to each shout, so you need to be able t match the separate words without the full shout.

The words need to be uppercase. A shout should only be matched, if it is a separate word, for example: Golf shouldn't be matched.

The separate words for the same shout in the order as in the list appear next to each other, then they need to be in the same match.

The input strings will only contain ASCII letters and spaces as word separators.

## Test cases

The matched text is bold

Hydrogen Sulphur Krah Coal Gaan Lah Haas

one two three four Kaal six seven Joor Zah Frul eleven

red green blue Gol Hah orange purple Qo violet

Ran Miir Taah Raan Mir Tah raan mir tah

Golf Gol Middleage Mid

## Rules

• The answer should be a .NET type RegEx and should not contain any other langauge.

• This is a code-golf, so the shortest answer in bytes wins

• Very closely related. What if a word appears in lower case in the input? What if it appears inside another word like Golf? If the latter should not be matched please clarify what characters can be in the input and which of those are valid word delimiters. All that said, I don't see anyone coming up with a good way to compress the words within the limit framework of regex. Jun 23 '16 at 12:18
• @MartinEnder I clarified it a but Jun 23 '16 at 13:16
• Still doesn't say what characters can appear in the input and what characters count as word separators (I'm assuming only letters and spaces, and spaces are separators, but if that's your intention you should say so explicitly, and if not, you should add further test cases). Looks good otherwise. To prevent confusion you might want to say explicitly that people should submit only a regex and which flavours are allowed (and whether flavours like Perl are allowed to make use of their eval features to execute code in the hosting language). Jun 23 '16 at 13:21
• If only one language is allowed this would limit the participation in your question. I don't understand why it should be only one language. Jun 29 '16 at 19:38
• @george I don't think you know what regex-golf is Jun 29 '16 at 19:44
• @Bálint Whoops I didn't see your title, my mistake. Jun 29 '16 at 19:47

## Find all the Vampire numbers

Shamelessly stolen from https://stackoverflow.com/q/17352108

A "Vampire" number is defined as the product of two numbers of equal length (known as the "fangs") that uses the same digits as the two numbers being multiplied. Examples:

21 * 60 = 1260
15 * 93 = 1395
30 * 51 = 1530


Your task is to find all the Vampire numbers whose fangs have n digits.

This is , so the shortest solution wins.

• What about double fangs, triple fangs etc? Jun 24 '16 at 11:30
• @DerpfacePython Double fangs? But I suppose I could generalise it to m fangs of n digits if there's enough support (and if there are actually solutions!)
– Neil
Jun 24 '16 at 12:19
• Related Jun 24 '16 at 13:23
• @FryAmTheEggman My bad for not searching first. I might as well delete this.
– Neil
Jun 24 '16 at 14:14
• I think all you have to do is add the double/triple fang thing and it probably is different enough? Not sure, but there is probably a way to get it to work. Jun 24 '16 at 14:20

## Title TBD - Generate Emoticons :)

Your task is to create a program that generates the most emoticons using the least amount of code.

### Rules

• The only valid emoticons are listed on Wikipedia, under the heading Western/horizontal emoticons: List of emoticons page (version 722951221)
• The output can be any format, as long as a delimiter exists between emoticons.

### Scoring

• Scores will reflect the character (not byte) count.
• For every emoticon after 10 that is output by your program, subtract 1 from your score. Emoticons over 20, subtract 2, over 30 subtract 3, and so on.

### Sandbox

Is the scoring fair/reasonable? Should I edit down the list/create a new list of acceptable emoticons?

# Forecast Romantic Dates

Sort of inspired by this.

A Romantic date is a date that, when the year, month and day are converted to Roman Numerals the individual values contain no more than two symbols. For example, in YY-MM-DD format: the Romantic date 20-04-15 would become XX-IV-XV.

For the purpose of this challenge, years will only be tracked by the two least significant digits of the year, as otherwise the last Romantic date was in the 15th century. In addition, they wouldn't add much to the challenge as the omissions of the leap year every 400 years is irrelevant, as February the 29th is not a Romantic date.

## Romantic dates

For your convenience, here is a list of all of the two digit numbers that can be represented with two or fewer symbols in Roman numerals:

[1, 2, 4, 5, 6, 9, 10, 11, 15, 20, 40, 50, 51, 55, 60]


These were determined using the "standard method" that negative groups would only be used with the symbols that are powers of ten and only on the values that are five or ten times that symbol's value. So I only combines with V and X for example.

Dates which include only numbers from this list are Romantic dates. For the purpose of this challenge, assume an ideal Western calendar: no dates are ever skipped or repeated, 12 months per year, and more than 20 days per month. Assume there is no year, month or day zero (i.e. year 99 loops to 1 not to 0).

## Task

Given a date as input, output that date if it is Romantic, or output the next Romantic date.

## Input and Output

You may accept input in any consistent ordering of year, month and day with any consistent separator. You may specify if the input should have the numbers padded to be two digits. If the numbers are padded, you may choose to have no separator. Your output must have the same form as your input.

## Test Cases

The following test cases are all in the format YY MM DD, with no padding.

1 1 1 => 1 1 1
20 4 3 => 20 4 4
15 7 1 => 15 9 1
51 9 7 => 51 9 9
70 9 7 => 1 1 1
20 6 24 => 20 9 1
47 12 1 => 50 1 1
60 11 24 => 1 1 1


Here is the script that I used to generate these.

## Sandbox

Did I miss any Romantic numbers? I just did that by hand.

Allow unary? I'm unsure about this because it sort of violates the reasoning behind Romantic dates for the values to have >2 symbols...

Should I explain more about parts of dates that are not useful? For example, the length of the months is entirely irrelevant as the later days are all skipped. My concern is that the current one feels clunky already

Should I allow both outputting the input if the date is already Romantic or the strictly next Romantic date (as long as it is consistent)? There doesn't seem to be much different, but I don't know if that'd be too broad? Personally leading towards allowing it.

I'm also somewhat tempted to make use of the silly title a bit more, but I'm not sure if that'd be going overboard.

Too boring / compression based? I've particularly been trying to think of a way for fewer results to wrap back around to 1.

• That rule should be spelt out explicitly in the question, because although some people insist on it it's a modern innovation. There are actual Roman inscriptions which do use e.g. IC. Jun 24 '16 at 21:05
• @PeterTaylor You're right, I originally left out the reasoning because I thought it might clutter up the spec, but I realise now I just left that comment undeleted to prevent people from asking the same question. I don't have time right now but I'll edit it in once I get a chance. Also, I figured it was better with this rule because I thought say VL was rather unintuitive, does that make sense or should I be more laissez-faire about it? Jun 24 '16 at 22:04

# Stacks and Stacks and Stacks...

Write a program that, with the input as n, finds the first n-gonal and n-gonal pyramid number that is NOT 1.

n is guaranteed to be larger than or equal to 3.

Examples:

• n = 3: 10
• n = 4: 4900
• n = 2: The output can be nothing, False, or anything that you want, just as long as it can be distinguished from an actual output.

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

### Bonus:

• If your code output both the name of the n-gon and the number: You get a big fat -50% off of your byte count (see below for examples).
• n = 4: Square 4900
• n = 3: Triangle 10
• n = 5: Pentagon ??? (the ??? is a placeholder because I have no idea what the number is)

### Meta:

• Is the bonus a good idea?
• I don't think the bonus is a good idea because 1) the name compression takes away from the original challenge and likely isn't worth it and 2) you haven't defined the naming scheme (e.g. 12-gon vs dodecagon) Jun 26 '16 at 7:10
• @Sp3000 Ah, OK. I really want to incorporate the use of strings in the challenge, but if the idea sucks, then I'll scrap it. Any further suggestions? Jun 26 '16 at 7:12
• Adding strings just makes it feel like squeezing two challenges into one, unfortunately. I'd recommend posting the shape names as a separate challenge, but I see we have this challenge. As for suggestions, maybe 1) remove the part about n = 2, since you already say n is guaranteed to be at least 3 and 2) maybe make it explicit that the output should be both n-gonal and n-gonal pyramidal (and maybe explain, say, that 10 is the 4th triangular and 3rd triangular pyramid number) Jun 26 '16 at 7:16
• Hmm my other problem is - what happens if there's no solution for a given n? Note the only reason I'm asking is because the number of solutions for any n could be finite, e.g. A027568. (6 is 946, 8 is 1045, 10 is 175 and 11 is 23725 I believe) Jun 26 '16 at 9:28
• Yeah, that could be a problem... maybe a time limit? Or maybe check numbers up to a given range. Jun 28 '16 at 6:50
• One alternative could be to allow solutions to potentially infinite loop/hit memory or recursion errors in the case of no solution/large solution. Numerical limit to check up to could work too, that'd probably be better than a time limit (since it reduces a dependency) Jun 28 '16 at 9:02
• @Sp3000 I would probably go with the numerical limit/memory limit thing, whichever comes first. But what about golfing/esoteric languages? There might not necessarily be a memory/numerical bound for those. Jun 29 '16 at 9:04

# Pyth Meta-Golf Golf Battery

(now that's a name, isn't it?)

## The Challenge

Write a program in a language of your choice that takes an input of code in the same language and outputs a code that does the same thing in Pyth (though not necessarily the shortest code).

## Rules

Given the test battery set below, you should try to find the best way to minimize your score with the following rules:

• You must minimize the source code of the submission.
• You may not used compressed versions of the input source for each test; the Pyth code must be output procedurally.
• The code must theoretically do the same conversion for any input code, not necessarily just these test cases.
• You must minimize the input code of each test.
• If an input is shown to be shortenable by without non-standard libraries of the submitted language, you must change it immediately to the shorter answer. If your answer does not support this change, then you must change your answer to accommodate.
• You may not submit answers written in Pyth.

Scoring is done with the following equation:

(source code)*((Pyth src out, test 1)/(input src in, test 1)+(same for test 2)+...)


## Objectives of each test

### Test 1:

Output the string "Hello, world!".

### Test 2:

Given an integer input, multiply that input by three and output it.

### Test 3:

Quine. (must be a valid quine in the submitted language and in Pyth)

### Test 4:

Produce infinite output.

### Test 5:

Cat program.

• I'm not a Pyth expert, but I strongly suspect that what this asks is impossible in many languages. E.g. I understand that Python's multi-threading support is extremely limited. Even if true impossibility is not an option, answers in many languages won't fit inside the 30000-character limit. E.g. I don't think the grammar for Java fits inside the limit, let alone a lexer and parser. Jun 27 '16 at 9:56
• I agree with Peter, that this seems like unless you use only trivial languages it probably won't be possible to answer. The scoring would also make this confusing: to make sure a solution is correct one would have to not only test 10 programs, you would also have to golf 5 programs. Further, there is a bit of a problem in Pyth's \$ operator, which runs literal Python, which means you should probably ban Python as well. I'm not really sure of how to turn this into a good question, too heavily restricting the type of program seems to be the only way, but it also seems to defeat the purpose. Jun 27 '16 at 13:09

# Don't even think about non-42-related numbers!

## Introduction and Credit

We all love our Answer to the Ultimate Question of Life, the Universe, and Everything which, of course is 42. So let's take this unworthy Fibonacci-Sequence thingy and adapt it to be worthy of 42!

## Specification

### Input

The input will be a positive integer.

### Output

The output will be either true or false.

### What to do?

Your task is to implement the predicate that the number under consideration is an element of the generalized Fibonacci-Sequence given by:

a_1 = 14
a_2 = 42
a_n = 41 * a_{n-1} + 43 * a_{n-2}


Where 42 is the ultimate answer, 41 and 43 are the primes next to it and 14 is the preceding catalan number.

### Potential corner cases

The number will always be greater than zero. Your program must pass all (32-bit) test vectors below.

### Who wins?

This is code-golf so the shortest answer in bytes wins!
Standard rules apply of course.

## Test Vectors

14 -> true
42 -> true
2324 -> true
4080622 -> true
97090 -> true
171480372 -> true
7 -> false
1 -> false
41 -> false
43 -> false

• a_3 is already outside the range of 8-bit unsigned integers, a_6 is outside the range of 32-bit signed integers, and a_11 is outside the range of 64-bit signed integers. It would be worth addressing this issue and at least ensuring that languages which are inherently 8-bit can't just special-case the two values which they can handle. Jun 25 '16 at 21:58
• @PeterTaylor I'm unsure how to formulate this without disqualifying legitimate approaches. Would saying "your program must pass all test vectors" (with 32-bit test vectors) also be considered OK for most people? Jun 25 '16 at 22:16
• I feel like this is too much two separate challenges: one to test for membership in the sequence, and the other to takeWhile on a condition. I also suspect the sequence has a direct arithmetic membership test like the one where n is a Fibonacci number exactly if either 5*n*n+4 or 5*n*n-4 is a square.
– xnor
Jun 25 '16 at 23:27
• What is takewhile? Jun 26 '16 at 7:02
• @xnor, I originally only wanted to do the takeWhile, but needed a (mediumly) complex, interesting predicate, so I came up with this one. Of course I'm open to suggestion for more suitable interesting predicates. Jun 26 '16 at 10:18
• @DerpfacePython, the higher-order functionality described in the second paragraph of "what to do?" is also called takewhile, I've clarified this though. Jun 26 '16 at 10:21
• @SEJPM I think the other way -- to do a challenge about takeWhile, make the predicate as simple possible. Beware chameleon challenges and needless fluff. One clean condition would be integers being positive.
– xnor
Jun 26 '16 at 10:56