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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

Search the Sandbox

Browse your pending proposals

Get the Sandbox Viewer to view the sandbox more easily

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

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2973 Answers 2973

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In this challenge you are supposed to output a grid 10x10 with numbers from 00 to 99 (each number once) following this rules:

  • Number 00 must be on the bottom row
  • Number 99 must be on the upper row
  • In the output each number must be sepparated by spaces and must have two digits (that is including 0's when needed for the first 10 numbers)
  • Output must be random
  • It must be solved within reasonable time

I'm having an issue trying to define random and reasonable time here and would like some help with it. Thanks.

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  • \$\begingroup\$ Define random as 'Each of the possible permutations must have an equal probability of being the output'. For reasonable time I don't think you need a definition - especially since your challenge is only 100 numbers, so it should be perfectly doable unless your algorithm works in O(n!). \$\endgroup\$ – Sanchises Apr 7 '16 at 11:11
  • \$\begingroup\$ @sanchises I find that asking for equal probability is too strong, since there's no way to prove that one of those algorythm has equal probability. \$\endgroup\$ – Masclins Apr 7 '16 at 16:34
  • \$\begingroup\$ Of course, a formal proof is not always easy. However, an intuitive result should be enough for most applications, and if people have difficulty with that, you can always use one of the algorithms described at the Wikpedia page, e.g. Knuth shuffling. I was wondering though, is there a motivation behind the challenge, or is just something you cooked up? \$\endgroup\$ – Sanchises Apr 7 '16 at 17:57
0
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Manual MD5

Given a string, calculate its MD5 sum without using any built-in MD5 library functions. An overview of the algorithm is here.

(I'm going to actually summarize the algorithm before I post it. Until then, it's still unfinished.)

Input is an ASCII string or byte stream with any reasonable length (I won't run an entire novel through your algorithm, for example).

Output the hex value of the resultant hash as a string.

Code golf, so shortest code wins. Standard loopholes are banned.

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  • 1
    \$\begingroup\$ You add the tags by adding [tag:code-golf] (and the others) to the body of your post. \$\endgroup\$ – user45941 Apr 2 '16 at 5:41
  • 1
    \$\begingroup\$ To answer your question: yes, include a description of the algorithm in the challenge body. Requiring external resources for a challenge is discouraged. \$\endgroup\$ – user45941 Apr 6 '16 at 4:02
  • \$\begingroup\$ 1. "Given a string, calculate its MD5 sum" is underspecified. In many languages nowadays, a string is a sequence of Unicode characters; MD5 is defined over sequences of octets, so to talk about the MD5 sum of a string you first have to define its encoding in octets. 2. Output format? \$\endgroup\$ – Peter Taylor Apr 8 '16 at 7:28
  • \$\begingroup\$ I clarified as ASCII string now in the input section. Should I mention that at the top, as well? \$\endgroup\$ – Value Ink Apr 8 '16 at 7:38
  • \$\begingroup\$ I think so. It's a one word addition and it avoids people wandering mentally off track. \$\endgroup\$ – Peter Taylor Apr 10 '16 at 21:46
0
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Matrix Multiplication

This is a challenge in which we will be multiplying matrices.

Input:

  • an n x m matrix, A
  • an m x p matrix, B
  • optional:
    • n, m, and p

Input may be in any convenient fashion in order to reduce/eliminate the need to parse input. In particular, it may be given via function argument. The matrix dimensions may be taken as input or may be deduced from the actual matrix input.

Output:

The product of the two matrices. That is, output the n x p matrix C such that A * B = C.

Scoring

Your score will be the average of the sum of times your program takes to multiply several test cases on my computer.

Basically, I:

  • Time your entry for each test case
  • Add up all the times
  • Repeat the above steps several/many times
  • Average all the sums
  • That average is your score

Rules and Restrictions

  • Built in array/vector/matrix multiplication functions are disallowed. If you have to ask if a built-in is allowed, it probably isn't (but please ask anyways).

    • However, once the test cases are up, I would like to see how MatLab compares to the given entries
  • Entries in A and B will be standard 16 bit signed integer. Entries in C will fit in 32 bit signed integers.

  • Matrix size/dimensions should be limited by mainly by my available memory.

  • The size of test cases is not yet determined. It will depend on the speed and memory requirements of entries. I will of course try my utmost to be fair.

  • I have 8G of RAM and an AMD64 cpu.

  • Languages must be freely available on linux. Please include instructions on how to compile/execute your code.

Notes

I'm really not sure how big the matrices will be, but I'm expecting dimensions in the 100's or 1000's.

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  • \$\begingroup\$ I think at slightly above 10000x10000 matrices you will run out of RAM, considering you'd have to store three of these matrices. MATLAB can multiply matrices of that size on my machine (similar specs) with a time of still only about 45 seconds. So I think memory is probably going to be the main limiting factor=) (And I do not think that anything's going to be much faster than BLAS) \$\endgroup\$ – flawr Apr 8 '16 at 23:45
  • \$\begingroup\$ @flawr I think 45sec would be long enough to get accurate timings. Also my machine is probably slower than yours and I doubt any entries will beat MatLab's time. If you think memory will still be a problem, I have no problem using 16 bit integers instead of 32 bit. \$\endgroup\$ – Liam Apr 9 '16 at 0:00
  • 1
    \$\begingroup\$ 1. Without knowing more about the test cases and the CPU it's going to be hard to optimise, because the sizes you're talking are roughly where the cutoff for naïve being worse than Strassen lies. 2. Can assembly answers use SIMD instructions (SSE etc.) or are they banned built-ins? \$\endgroup\$ – Peter Taylor Apr 10 '16 at 21:41
0
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Iterated Matrix Multiplication

Given an nxn matrix A, an nx1 matrix X, and a list L of ordered pairs in [0,n)x[0,n), determine if there exists some integer k>=0 such that, with B=A^k*X, for all (D,E) in L, B[D]<B[E].

Why it's possible: Every entry of the natural number power of a general matrix can be expressed via sums of multiples of powers of the matrix's eigenvalues, like 2^k+4*6^k-10*3^k, and for any two such expressions, there will always be some k beyond which one term dominates the expression, and the sign of their difference can no longer change, so one way to solve the problem would be to calculate that k.

Test cases:

[[1,2],[2,3]],[3,4],[(0,1)] -> Yes (k=0)
[[1,2],[2,3]],[3,4],[(1,0)] -> No
[[1,2],[2,3]],[4,3],[(1,0)] -> Yes (k=0)
[[1,2],[2,3]],[4,3],[(0,1)] -> Yes (k=1)
[[1,-2],[2,-3]],[3,4],[(1,0)] -> Yes (k=1)
[[-1,-2],[2,-3]],[3,4],[(1,0)] -> Yes (k=2)
[[-1,-2],[2,-3]],[3,4],[(1,0),(0,1)] -> No
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  • 1
    \$\begingroup\$ 1. For fastest-code you need to describe how you will measure it, selecting a test size which is large enough to give meaningful differences but small enough to be feasible. That probably means that you need to write a reference implementation or three (trying difference approaches). 2. For floating point questions, you need to do some numerical analysis to determine on what range of input it's feasible to write a correct program, and then guarantee that the input will be within that range. 3. You need to think about what level of library support is fair. \$\endgroup\$ – Peter Taylor Apr 13 '16 at 8:54
0
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Colorize!

In Ruby, the colorize gem allows you to output text to the terminal in pretty colors:

Blue, bold text saying "This is a box"

It uses the ANSI color standard to tell the terminal how to color things, then trusts that the terminal will do the right thing. For this challenge, you can too.

What you'll do is take a a pair of lidts of strings, in whatever format you want. For example, if you wanted comma-separated values:

+-----+,| box |,+-----+
red,blue,red

The first list is what you'll be colorizing. The second list is a list of color names that are the same as the ones in the Wikipedia article. You'll colorize each string from the first list with the respective color from the second. The two lists will always have the same number of items, and the second will only ever contain valid color names. The strings in the first will only contain valid, printable ASCII characters.

And apply those colors -- as given by the ANSI standard linked above -- to the text, printing each string on its own line. For example, with this (heavily ungolfed) code:

#to be written

you'd get this:

[picture of result]

You may not use any libraries built to do this, and the standard loopholes are disallowed.


I'm thinking of adding extra credit for bolding/doing multiple things at once. Is that a good idea?

Aside from that, how is the rest of the challenge?


To-do list:

  • Copy the list from Wikipedia to here
  • Add pictures, demo code
  • Add that you have to change the color back to default at the end
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  • \$\begingroup\$ The comma separated thing seems unnecessary, in most languages this just adds a boring split(',') call. You also probably want to only allow printable ASCII in the body of the strings (or at least put some restriction otherwise stuff can get pretty hairy). In addition you should explain what is necessary to know from the ANSI standard in your question body. \$\endgroup\$ – FryAmTheEggman Apr 13 '16 at 13:03
  • \$\begingroup\$ @FryAmTheEggman I linked the relevant part and stated "ANSI color standard" when it was first mentioned. What input format would you suggest that can deliver a set of lines to colorized and a set of colors to use? \$\endgroup\$ – Fund Monica's Lawsuit Apr 13 '16 at 13:22
  • \$\begingroup\$ Just say what they are: a list of strings and a list of colours. The link doesn't matter: if Wikipedia is down or they change that page so it doesn't help here then I can't answer your question without guessing what you mean. Also, the reason I said printable ASCII is that some ASCII is still hard to deal with. What about control characters, etc.? \$\endgroup\$ – FryAmTheEggman Apr 13 '16 at 13:27
  • \$\begingroup\$ @FryAmTheEggman Oh, I see. I'll update it to have "input of two lists in whatever format you want" and "printable ASCII characters only". As for requiring Wikipedia to be up, I'll copy and paste it when I have time. However, note that ANSI's standards are available online, and Googling "ANSI color standard" yields their website as well. Wikipedia is far more readable. \$\endgroup\$ – Fund Monica's Lawsuit Apr 13 '16 at 13:32
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I'm a Puzzle!

Your task is to print the string "I'm on OS!", where OS is the operating system that the program is run on without version numbers.

Standard loopholes apply.

In addition, programs with hardcoded values (e.g. print "I'm on AFakeOS") will be disqualified.

As this is Code Golf, your score will be the length of your full program.


Any suggestions?

Java example:

class A {
    public static void main(String[] args){
        System.out.println("I am a " + System.getProperty("os.name").replaceAll(" .*","")
                                     + "!");
    }
}
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  • 5
    \$\begingroup\$ When making something in Java, "noncompetitive" is implicit. \$\endgroup\$ – Cyoce Feb 13 '16 at 7:31
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    \$\begingroup\$ :P I've been lurking and waiting for an idea long enough to know. \$\endgroup\$ – 0az Feb 13 '16 at 13:07
  • \$\begingroup\$ "If run in a browser (JavaScript and/or any other browser scripting languages), the browser should be output instead." Why is that? I'm pretty sure you can detect the operating system even if you're in a browser. \$\endgroup\$ – Martin Ender Feb 13 '16 at 17:40
  • \$\begingroup\$ And my suggestion for "other bonuses, penalties, ..." is drop all of them. \$\endgroup\$ – Martin Ender Feb 13 '16 at 17:40
  • \$\begingroup\$ Added Java example solution. Removed bonuses. Read the linked question. \$\endgroup\$ – 0az Feb 13 '16 at 21:32
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    \$\begingroup\$ Exactly what is acceptable output? If Windows 10, is Windows? Windows 10? Windows NT Version 10.[build n]? \$\endgroup\$ – lirtosiast Feb 14 '16 at 5:24
  • \$\begingroup\$ How portable does this need to be? E.g. would uname -o be acceptable? \$\endgroup\$ – Peter Taylor Feb 15 '16 at 12:46
  • \$\begingroup\$ Considering that uname prints Darwin on my MacBook, and -o is an illegal option, uname -o would not work. I guess a possible definition of portable would be "works correctly on OS X, Windows, and most of the more common Linux distros" \$\endgroup\$ – 0az Apr 18 '16 at 3:01
  • \$\begingroup\$ @alphadelta That entails unambiguously defining the operative words most of the and more common in the phrase most of the more common Linux distros, which is objectively impossible. \$\endgroup\$ – cat Apr 24 '16 at 2:14
  • \$\begingroup\$ Perl 5, fourteen bytes as a subroutine: {"I'm on $^O!"} (where ^O is actually the F byte). (Fifteen as a program that prints: say"I'm on $^O!".) I can only imagine that the golfing languages will get down to one or two bytes, then. :-) \$\endgroup\$ – msh210 Apr 26 '16 at 22:32
0
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@Sandbox:

  • Not sure if is correct here.
  • Do I need test cases for this? They will make this very lengthy.

Tags:

Find the structs!

The Challenge

Given a piece of C-code, add a /* before and a */ after every top-level structure definition that you find. You may not do this for structures that are defined inside other structures.

  • A structure can be identified by the struct keyword followed by an identifier, an opening {, some alphanumeric characters inside the structure and a closing };.
  • A structure identifier will only consist of alphanumeric characters.
  • One structure may also contain other structures with an unlimited depth.
  • Comments and whitespaces may appear anywhere in the code and have no effect. // starts a single line comment and code enclosed in /* and */ is a multiline comment.
  • You can't rely on a specific indentation style.
  • A structure will not contain any braces {} that are not part of another structure definition.
  • There can be multiple top-level structures in the input. You have to consider them all.
  • The input will only contain printable ASCII and newlines.

Example

So the output for

int z;
struct example1 /* comment here */  {
    int x; // struct comment {int x;};
    struct nested
    {
        char* s;
        int* y;
    };
};
int y;

//struct { };

struct example2{int x;};

would be

int z;
/*struct example /* comment here */  {
    int x; // struct comment {int x;};
    struct nested
    {
        char* s;
        int* y;
    };
};*/
int y;

//struct { };

/*struct example2{int x;};*/

Rules

Happy Coding!

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  • 1
    \$\begingroup\$ I think this has some problems, as most questions that say "Given some C code do...", with what counts as valid. What about things like trigraphs, or macros or... ? \$\endgroup\$ – FryAmTheEggman Apr 13 '16 at 17:56
  • \$\begingroup\$ @FryAmTheEggman So it would be fine, when I limit the possible code-contents to a certain subset of C like I did for the struct contents? \$\endgroup\$ – Denker Apr 13 '16 at 19:00
  • \$\begingroup\$ Yeah, but I'm not well versed enough in C grammar to be able to say for sure that that'll be enough. \$\endgroup\$ – FryAmTheEggman Apr 13 '16 at 19:05
  • \$\begingroup\$ @FryAmTheEggman Thought about this and I actually don't need all that C-syntax stuff. Just came from the origin of this, but it's no really needed. Should be clear now. \$\endgroup\$ – Denker Apr 13 '16 at 20:23
  • \$\begingroup\$ Please work on your spelling before posting this, if you do. \$\endgroup\$ – Fund Monica's Lawsuit Apr 14 '16 at 18:52
  • \$\begingroup\$ @QPaysTaxes You can't fault OP for speaking ESL; this is why anyone can edit posts on SE. \$\endgroup\$ – cat Apr 24 '16 at 1:20
  • \$\begingroup\$ @cat That's actually wrong. You can't suggest edits on meta, and this answer isn't CW, so I'm not able to edit this. If you'd like to confirm, take any of your accounts with less than the required rep, go to meta, and try to edit something. It doesn't let you. \$\endgroup\$ – Fund Monica's Lawsuit Apr 24 '16 at 2:04
  • \$\begingroup\$ @QPaysTaxes I'm aware there are no suggested edits on Meta, because that would mean more, more clogged review queues for popular sites. I meant when the challenge is posted which is the only time small grammar things will matter anyhow, and I tend to be the type to fix that stuff. \$\endgroup\$ – cat Apr 24 '16 at 2:08
  • \$\begingroup\$ @cat Oh, I see. I thought you meant I should edit the Sandbox post, which... I can't. I've been told several times to "just edit it!" on various Metas where I don't have permission; I have yet to be told "edit it when this is on main" :P \$\endgroup\$ – Fund Monica's Lawsuit Apr 24 '16 at 2:11
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Spiral text

Write a function or program that given a text with one or more characters in it outputs the text as a square spiral. The first letter of the text must be the center of the spiral and then all the characters must follow a clockwise spiral pattern as follow, striping all white spaces:

           789[10]
           612[11]
           543[12]
              [13]

Example

Input: Hello World!
Output:

               ORLD
               WHE!
               OLL

The text could be any length. Please validate with the following texts:

Once upon a time

Expected output:

o   n   a   t
p   o   n   i
u   e   c   m
            e


Tyger Tyger, burning bright, In the forests of the night; 

Expected output:

g   h   t   ;           
i   i   g   h   t,  I   n
n   r   y   g   e   r   t
e   b   t   t   y   ,   h
h   g   r   e   g   b   e
t   n   i   n   r   u   f
f   o   t   s   e   r   o

The minimung length of the input text is one character.

Note: Somewhat similar to this question

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  • \$\begingroup\$ Test cases are more useful if you also include the expected output. ;) \$\endgroup\$ – Martin Ender Apr 29 '16 at 9:16
  • \$\begingroup\$ @MartinBüttner yay! Doing that \$\endgroup\$ – Averroes Apr 29 '16 at 9:17
  • 1
    \$\begingroup\$ Also having to support the empty string seems like an annoying special case that isn't likely to add anything interesting to most answers, so I'd personally probably let the input have at least one character, but that's your call. \$\endgroup\$ – Martin Ender Apr 29 '16 at 9:18
  • \$\begingroup\$ When you say "somewhat similar": why should I not vote to close it as a duplicate? It seems that the only difference is a reflection in the leading diagonal, which I would class as trivial. \$\endgroup\$ – Peter Taylor Apr 29 '16 at 11:55
  • \$\begingroup\$ @PeterTaylor First of all the other question doesn't have any answer and it is a bit old so maybe now this question can get a little more audience now. Secondly the other question add "The characters can spiral into previous characters" that this doesn't add to the specs so I think they are different questions. \$\endgroup\$ – Averroes Apr 29 '16 at 12:39
  • \$\begingroup\$ Ok, the other question is horrible. This is actually more like various spiralling numbers questions, with the main difference being that it spirals outwards rather than inwards. \$\endgroup\$ – Peter Taylor Apr 29 '16 at 12:52
0
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Is this a helpful starting layout?

My computer has a Patience-style card game installed on it. It takes two packs of cards, removes the Aces, shuffles them, and deals 8 cards.

In order to maintain my 100% perfect completion record, I want as helpful a starting layout as possible. Deuces are immediately playable, so they are helpful cards. However other cards can only be played on cards of descending rank and opposite colour, which means that cards of the same rank and colour unhelpfully clog up the layout.

The challenge is to write a program or function which accepts a string or list of eight cards and outputs a truthy or falsy value. Cards are identified by their rank, which is one of the characters 23456789TJQK, and their suit, which is one of the characters CDHS. (Note that using numbers 10-13 for the rank is not an acceptable input.) For a layout to be helpful there must be at least one Deuce of any rank, and (except Deuces) there must not be any pairs of cards with the same rank and colour. Examples:

4H7STHTD5C5D2HQS -> unhelpful because of two red Tens
TD8S4CKC4HKD5S5H -> unhelpful because of no Deuces
2H7SJH3S4HKS7H3H -> helpful layout

This is , so the shortest program wins.

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  • \$\begingroup\$ At first I thought this was a request for help, not the setting for a problem. You'll want to add what those inputs mean, what "a helpful layout" means, in detail. \$\endgroup\$ – Fund Monica's Lawsuit May 2 '16 at 18:19
  • \$\begingroup\$ As I understand, this can be solved by checking if the string contains 2 and its chunks of two are distinct, which seems pretty straightforward. \$\endgroup\$ – xnor May 3 '16 at 11:46
  • \$\begingroup\$ @xnor Not quite distinct, since a) you have to ignore the chunks that contain 2 and b) H==D and S==C for the purposes of comparison. \$\endgroup\$ – Neil May 3 '16 at 11:57
0
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Solve for the Operators

In this challenge, you will be given a bunch of numbers and an answer. Your job is to find a sequence of operators that will successfully solve this equation. Use the numbers in the order that they are given

Operators: +, -, *, /

For example,

Numbers given: 2, 6, 8, 4, 5

Answer: 9

2__3__8__4__5 = 9

The program should find which operators can be used in the blanks to make the equation true. Remember Order of Operations Matters (PEMDAS)

Output:

2*3-8/4+5 = 9

Only 1 solution is needed per problem

Rules

  1. No built-in math functions beyond operators.
  2. Must Follow Order of Operations
  3. Must give one correct output.
  4. Least Number of Bytes Wins.

Examples:

Numbers: 4, 4, 4, 4

Answer: 0

4 - 4 + 4 + 4 = 0

Numbers: 1, 8, 6, 4, 5, 2, 3, 3

Answer: -35

1*8+6-4*5*2-3*3 = -35

Numbers: 1, -2

Answer: 3

1--2 = 3
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  • 2
    \$\begingroup\$ In many languages, this will just be "find the cartesian product of +-*/ repeated as many times as there are blanks with itself, insert them over the blanks and call eval". It's fine if you want that, but it seems somewhat, uh, boring? \$\endgroup\$ – FryAmTheEggman May 5 '16 at 13:26
  • 1
    \$\begingroup\$ 4 - 4 + 4 + 4 = 8 \$\endgroup\$ – trichoplax May 5 '16 at 13:30
0
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Make a times table sheet

The challenge is to make an ascii art version of a times table sheet.

Look at the following:

times tables.

Your answer should have the same layout as this table:

  • You should not include the title or the footer or worry about colors. Black and white is fine.
  • The times tables lines in each box should be randomly ordered.
  • You should include all the horizontal and vertical lines in the image (except in the header and footer).
  • The equals signs should be aligned in each column as in the example above.
  • It should be in ASCII art.

I am not worried about the precise spacing as long as the layout is as specified.

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  • \$\begingroup\$ no ascii art for me? \$\endgroup\$ – Leaky Nun May 6 '16 at 17:41
  • \$\begingroup\$ @KennyLau I could make it ASCII art if people love that. \$\endgroup\$ – user9206 May 6 '16 at 18:22
0
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Challenge

Create a factor tree from a number. A factor tree will take a number > 1, n, and find 2 numbers that multiply together to equal n that are greater than 1. Then, it will repeat for the factors until every section reaches a number that does. Then it will output the last numbers.

For example:

enter image description here

Examples:

Input: n = 20

Graph(This is not the output):

enter image description here

Output: 2x2x2x3

Input: n = 54

Output:2x3x3x3

Input: n = 72

Output: 3x3x2x2x2

Input: n = 2

Output: 2

Scoring

Shortest bytes wins.

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  • 1
    \$\begingroup\$ I think you mean a factor tree, not factorial. That is very different. \$\endgroup\$ – Rɪᴋᴇʀ May 7 '16 at 3:11
  • \$\begingroup\$ @EᴀsᴛᴇʀʟʏIʀᴋ yes that is what i meant. Thank you \$\endgroup\$ – JoshK May 7 '16 at 3:18
  • \$\begingroup\$ Would it be more interesting if i had the output be the tree instead of the numbers? \$\endgroup\$ – JoshK May 7 '16 at 3:20
  • \$\begingroup\$ yeah, I think the numbers is probably a dupe. Plus, it would be more fun/hard. (hard isn't bad) \$\endgroup\$ – Rɪᴋᴇʀ May 7 '16 at 3:20
  • \$\begingroup\$ I recommend having output be a image/ascii art, though that needs more specifications. \$\endgroup\$ – Rɪᴋᴇʀ May 8 '16 at 20:31
  • \$\begingroup\$ As it stands, this is a duplicate of codegolf.stackexchange.com/questions/1979/factorize-me \$\endgroup\$ – user45941 May 13 '16 at 5:27
0
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Inverse Square Probability

It's a fairly well-known fact that the sum of the reciprocals of squares is equal to pi squared divided by 6. That is,

Basel Problem

This is the Basel problem and was solved by Euler in 1735. I was thinking about generating a random patchwork of squares and trying to decide how to weight the probabilities of different square sizes, when it occurred to me that I could use this fact and make the probability of choosing a square's size be the inverse of its size.

For instance, if I pick a random point on the interval [0..pi^2/6), then based on the point I pick, r, I can translate it to a square size in the following manner (all numbers rounded to 3 decimal places):

0     <= r < 1     => s = 1
1     <= r < 1.25  => s = 2
1.25  <= r < 1.361 => s = 3
1.361 <= r < 1.424 => s = 4
1.424 <= r < 1.464 => s = 5
...

Your program or function should work for any input within the limits of your language (for instance, floating point precision, lack of built-in bignum capabilities, etc). Input will always be 0 <= r < pi^2/6.

Test Cases

{to be added}
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0
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ASCII Hulls


Input

A string containing a rectangle made up of m rows of n characters, separated by newlines. Apart from an optional trailing newline (which you may choose), the string must contain nothing else.

All the characters will be printable ASCII (including space). So ASCII characters 32 to 176 inclusive.

The dimensions m and n will not be specified in the input. They will both be in the range 1 to 80 inclusive.

Output

A string containing the same rectangle but with the convex hull of each non-space character filled with that character, higher ASCII values overwriting lower ones.

Overwriting does not prevent a character from contributing to the convex hull. For each character, the convex hull is defined based on the locations of that character before any overwriting.

Details

The rectangle of characters forms a grid of m squares by n squares. The vertices of the convex hull for a given character are the centres of the squares containing that character (apart from any in the interior of the convex hull). All squares whose centre is on the convex hull or in its interior become that character (until any overwriting).

Outline showing convex hull Filled convex hull

Equivalently you can use the top left corner instead of the centre (or any other point in the square) provided it is consistent. This will give the same output.

Test cases

Input followed by output in a single code block

P    
   P
 P  

P    
 PPP
 P


C    C

      G    G
    C    C

   G    G

CCCCCC
  CCCCC
   CCCGGGGGG
    CGGGGGG
    GGGGGG
   GGGGGG


 W    Z
X      X


Y      Y
 W    Z

 W    Z
XXXXXXZX
 W    Z
 W    Z 
YYYYYYZY
 W    Z

Scoring

The shortest code in bytes wins.

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  • \$\begingroup\$ I don't understand what the "convex hull" is here. Could you give an example? \$\endgroup\$ – Nathan Merrill May 10 '16 at 21:55
  • \$\begingroup\$ @NathanMerrill It's a convex hull I think. \$\endgroup\$ – Fund Monica's Lawsuit May 10 '16 at 22:02
  • \$\begingroup\$ @NathanMerrill I added some test cases to visualise it \$\endgroup\$ – trichoplax May 10 '16 at 22:08
  • \$\begingroup\$ @NathanMerrill I added a diagram which hopefully sums it up better \$\endgroup\$ – trichoplax May 10 '16 at 22:52
  • \$\begingroup\$ How do you decide if a letter is within the hull? For example, it seems like the first should be P / PPPP / _PP, because part of the square between the midpoints of each letter is crossed. \$\endgroup\$ – Fund Monica's Lawsuit May 10 '16 at 23:11
  • \$\begingroup\$ @QPaysTaxes All squares whose centre is on the convex hull or in its interior become that character so it isn't enough for part of the square to be crossed - the centre of the square has to be on or within the convex hull. \$\endgroup\$ – trichoplax May 10 '16 at 23:28
  • \$\begingroup\$ Oh, I see. That makes more sense.r \$\endgroup\$ – Fund Monica's Lawsuit May 10 '16 at 23:58
  • \$\begingroup\$ I'm having a bit of trouble deciding for this one, but apart from the fact that there's multiple hulls and ASCII parsing/writing involved, is the core of the challenge any different from existing convex hull challenges? \$\endgroup\$ – Sp3000 May 11 '16 at 5:09
  • \$\begingroup\$ @Sp3000 unless the need to keep track of where the initial characters were while doing the overwriting for other characters adds anything in terms of golfing challenge, then I guess this is a duplicate \$\endgroup\$ – trichoplax May 11 '16 at 14:35
0
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Triangle Rasterization

I don't know if this is the right word for this, but here goes...

Given a triangle with a height and a width, you can convert it into squares by counting any square that the triangle occupies as a whole square. Your task is to calculate the area of this 'rasterized' triangle.

Your program should take two positive integers representing the height and width of a triangle and output the area of its 'rasterized' version. This should always be an integer.

No builtins are allowed, if there are any.

An example

What I'm actually talking about. This is a 6x4 triangle. The red area is the actual inside of the triangle, and the blue area is added on during the 'rasterization'. The total are of the red and the blue is 16. So, given 6 and 4 as inputs, your program must output 16, with or without a trailing newline.

Test cases

 input     output
 1, 1      1
 1, 2      2
 1, 3      3
 2, 2      3
 6, 4      16
 63, 47    1512

As you can probably tell, this is slightly larger than half the area of the enclosing rectangle, and gets more accurate for larger sizes.

Your program should preferably run in under a minute, but the answer with the shortest number of bytes will win.

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  • 1
    \$\begingroup\$ Are you sure about the test case 63, 47? I make it 1535. \$\endgroup\$ – Peter Taylor May 12 '16 at 22:16
  • \$\begingroup\$ @PeterTaylor while fiddling around with a solution I made, I think this error comes from rounding poorly. When I tried adding 1 to each column with a non-integer value and then flooring (I believe this is equivalent to taking the ceiling) I got your answer, but when I tried adding .5 to each value and then flooring I got the value the OP got. For reference: ceil and flop \$\endgroup\$ – FryAmTheEggman May 13 '16 at 18:01
0
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"45-degree rotation" of a square matrix


Introduction

Suppose we have a square matrix with odd sidelength, like this:

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

Let's divide it into nested layers as follows:

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

The nth layer, counting from the center, contains 8*(n-1) cells, and we rotate it n-1 steps in the clockwise direction:

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

Now our original matrix has been "rotated by 45 degrees", in a sense:

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

Namely, if this operation is applied twice, the result is a 90-degree rotation.

The task

Your input is an n×n matrix of single-digit integers, where n is odd, in any reasonable format. Your output is the 45-degree rotation of this matrix, as defined above.

Rules and scoring

You can write a full program or function. The lowest byte count wins, and standard loopholes are disallowed.

Test cases

[[3]] -> [[3]]
[[1,2,3],[4,5,6],[7,8,9]] -> [[4,1,2],[7,5,3],[8,9,6]]
[[0,1,2,3,4],[5,6,7,8,9],[0,1,2,3,4],[5,6,7,8,9],[0,1,2,3,4]] -> [[0,5,0,1,2],[5,1,6,7,3],[0,6,2,8,4],[1,7,8,3,9],[2,3,4,9,4]]
[[1,0,0,2,0,0,3],[0,1,0,2,0,3,0],[0,0,1,2,3,0,0],[4,4,4,5,0,0,0],[4,4,4,4,0,0,0],[4,4,4,4,0,6,7],[4,4,4,4,0,8,9]] -> [[4,0,0,1,0,0,2],[4,4,0,1,0,2,0],[4,4,4,1,2,0,0],[4,4,4,5,3,3,3],[4,4,4,0,0,0,0],[4,4,0,6,0,0,0],[4,0,8,9,7,0,0]]
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0
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KOTH Screeps Fighting AI

Screeps is an MMO for programmers (not a regular MMO, this is not modding, but rather the only way to play) where you program creeps. I want to make sure one more time: this is not hacking or modding, this is the only way you play the game. It has a builtin IDE that is always present.

This is your job: With 1550 energy, spawn an army of creeps to fight other player's armies. Your goal is to destroy the other team's spawn.

Specifications

  • Each team will start with 0 creeps and it's own spawn.
  • The team number will be hardcoded.
  • The spawns will be named Spawn1 and Spawn2, corresponding to each player's team
  • The room controller will be at level 8 and you will not have to worry about upgrading it.
  • Each creep will display an emoji chosen to represent it's team using creep.say(). This is so that members of the two teams can distinguished.

Rules

  • Not all creeps have to fight. Some can gather energy, build walls, etc.
  • Building structures is allowed. This includes walls, ramparts, towers, etc.

This is under construction! Please comment if you know how to improve this challenge!

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  • \$\begingroup\$ I recall that in your purely energy gathering Screeps challenge, the example room could be used that did not require paying or creating an account. What is the situation with this new challenge? \$\endgroup\$ – trichoplax May 17 '16 at 19:20
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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

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0
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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?

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  • \$\begingroup\$ Related, related. \$\endgroup\$ – Leaky Nun May 22 '16 at 1:28
  • \$\begingroup\$ 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) \$\endgroup\$ – Sp3000 May 22 '16 at 4:25
  • \$\begingroup\$ Just to double check, does "Each fragment can be used any number of times." mean that cancan, [can] -> True? \$\endgroup\$ – Sp3000 May 22 '16 at 6:45
  • \$\begingroup\$ I see a typo: "cat" isn't in the list but "tar" is twice \$\endgroup\$ – user46167 May 22 '16 at 20:18
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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.
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0
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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.
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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
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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.
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  • \$\begingroup\$ 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. \$\endgroup\$ – Geobits May 25 '16 at 2:58
  • \$\begingroup\$ @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... \$\endgroup\$ – Hooked May 25 '16 at 3:05
  • \$\begingroup\$ 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. \$\endgroup\$ – Geobits May 25 '16 at 3:08
  • 1
    \$\begingroup\$ I foresee arguments over where exactly the line falls for "hard-cod[ing] the rules to Fizzbuzz". \$\endgroup\$ – Peter Taylor May 25 '16 at 11:45
  • \$\begingroup\$ Hmmm....if you come up with arbitrary rules of fizzbuzz (like different numbers, different amounts of numbers), that might work to prevent hardcoding. \$\endgroup\$ – Nathan Merrill May 25 '16 at 14:24
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Code me music

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.
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  • \$\begingroup\$ 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. \$\endgroup\$ – FryAmTheEggman May 27 '16 at 14:35
  • \$\begingroup\$ @FryAmTheEggman Thank you for your feedback, updated challenge. \$\endgroup\$ – lapras May 27 '16 at 14:54
  • \$\begingroup\$ Yes, this is already a challenge. (And, curiously, the second sandbox proposal which is a variant on that challenge in just a week). \$\endgroup\$ – Peter Taylor May 28 '16 at 10:55
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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.

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  • \$\begingroup\$ 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) \$\endgroup\$ – Geobits Jun 4 '16 at 19:02
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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.
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  • 1
    \$\begingroup\$ 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? \$\endgroup\$ – Sp3000 Jun 5 '16 at 6:50
  • \$\begingroup\$ 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. \$\endgroup\$ – trichoplax Jun 6 '16 at 13:52
  • \$\begingroup\$ I think this could be an interesting challenge, but it needs to be well defined before it will be ready. \$\endgroup\$ – trichoplax Jun 6 '16 at 13:57
  • \$\begingroup\$ It is code-golf. \$\endgroup\$ – user54200 Jun 6 '16 at 14:01
0
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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.

Example

[ 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?
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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

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  • \$\begingroup\$ 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. \$\endgroup\$ – Peter Taylor Jun 7 '16 at 11:02
  • \$\begingroup\$ 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. \$\endgroup\$ – Nacht Jun 7 '16 at 23:28
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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?
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  • \$\begingroup\$ 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? \$\endgroup\$ – Peter Taylor Jun 9 '16 at 9:42
  • \$\begingroup\$ @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. \$\endgroup\$ – Alconja Jun 9 '16 at 11:09
  • \$\begingroup\$ @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). \$\endgroup\$ – Alconja Jun 9 '16 at 11:11
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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.

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  • 2
    \$\begingroup\$ Closely related. \$\endgroup\$ – Leaky Nun Jun 10 '16 at 13:56
  • \$\begingroup\$ 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). \$\endgroup\$ – AdmBorkBork Jun 10 '16 at 13:59
  • \$\begingroup\$ 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. \$\endgroup\$ – A Simmons Jun 10 '16 at 13:59
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