Sandbox for Proposed Challenges

Question

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".

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• Most people include applicable tags in their proposal, so for instance you can search for all king-of-the-hill proposals by merely adding the tag name in quotes to the search query.

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

Answer 1

Could it all add up to nothing?

Given an input number, return a truthy value if it is possible to arrange permutations of + and - signs to make the sum of the range up to that value 0.

Note that you don't have to output which set of combinations is truthy.

Test cases:

1 (1) --> Falsy
2 (1,2) --> Falsy
3 (1,2,3) --> 1+2-3, Truthy
4 (1,2,3,4) --> -1+2+3-4, Truthy
5 (1,...,5) --> Falsy
6 (1,...,6) --> Falsy
7 (1,...,7) --> 1+2-3-4+5+6-7, Truthy
8 (1,...,8) --> 1+2-3-4-5-6+7+8, Truthy

Just one thing - no using eval or similar commands.

This is code-golf so the shortest answer in bytes wins!

Sandbox notes

Require a range or a list as input?

Answer 2

Grow and Visualize Decision Tree

META: work in progress...

• Would providing the points as an image instead of a list of coordinates simplify the challenge?

code-golfgraphical-outputgraph-theorymachine-learning

Given two sets of points in the plane with coordinates x,y, both in [0,1), grow a (binary) decision tree as specified below and output a square pixel image of a given size, that visualizes the corresponding tree.

How to grow the tree

The we call the two sets here classes and follow the following recursive approach:

1. If at least one of the classes is empty, label the current node as a leaf of the nonempty class and stop. Otherwise:

2. First find the mean of each of the x (or y)-coordinates of each of the two classes, and find the mean/center c of those two means. Then we partition both classes as follows: All points with an x (or y)-coordinate strictly smaller than c belong to one half, all the other ones to the other half. The we set the current node to the decision is the x-cooridinate (or y-coordinate) less than c?

3. For each of the halves, go back to step 1 and 2, and set the resulting nodes as the child nodes from the current node. If you previously considered the x-coordinates, then consider y-coordinates and vice versa.

How to visualize the tree

We partition the the unit interval [0,1) into N equidistant sub intervals [0,1/N), [1/N,2/N), [2/N,3/N)... and correspondingly the unit square [0,1)x[0,1) into squares

[i/N,(i+1)/N)x[j/N,(j+1)/N) for i,j=0,1,2,...,N-1

which later will be represented by a pixel. For each square [i/N,(i+1)/N)x[j/N,(j+1)/N) we classify the point i/N,j/N with the tree we just grew and colour the corresponding pixel with the corresponding colour.

For the example above the output would look like so:

Details

• Input: An integerN>5 and two sets of points in any convenient format (e.g. as two separate list of points, or as a single list with a label for each point etc.) You can assume that in total there is at least one point.
• Output: A pixel image (vector images composed of squares are ok too) of the visualization.
  • You have to choose any two distinct colours, I recommend blue and red.
  • The x-axis should point to the right, the y-axis can point in any direction.
  • The submission should display the image on the screen or save it to a file (like jpg/png/tiff or similar formats)

Answer 3

Make a sequence from a sequence!

(Title is bad and I should feel bad)

Given a sequence of positive Integers, take each consecutive pair of two (without taking an element two times) (x,y) and print y x times.

For example for 3,1,4,2

1. Pairs are (3,1) and (4,2)
2. (3,1): Print 1 three times: 1 1 1
3. (4,2): Print 2 four times: 2 2 2 2
4. Resulting sequence/output is 1, 1, 1, 2, 2, 2, 2

Input

A sequence of positive integers divisible by two. This can be done by parameters, a flat array, an integer stream etc. AS LONG AS there's no nesting or pre-matching of pairs involved.

Output

The resulting sequence as showcased above. Same rules for datatypes as declared in input, keep everything flat.

Test cases

      3, 1, 4, 2 => 1, 1, 1, 2, 2, 2, 2
            6, 5 => 5, 5, 5, 5, 5, 5
1, 1, 1, 1, 1, 1 => 1, 1, 1

Reference Implementation (Ruby, 55 bytes)

f=->a{a.each_slice(2).collect{|x|Array.new *x}.flatten}

Ungolfed:

def g *a
  a.each_slice(2).collect do |x|
    Array.new(x[0], x[1]) 
  end.flatten
end

The first golfer to find a shorter solution in this language gets a -1 bonus.

Scoring

Shortest code in bytes wins.

Answer 4

CAPTCHAs (Cops and Robbers Style)

cops-and-robbers

Cops will write a program that generates a CAPTCHA (either through stdin/stdout or on whatever UI is available to your language using only built-ins).

Robbers will attempt to bypass the generated CAPTCHA programmatically, given access to the Cops' programs' stdin/stdout or UI process/thread (for example, in JavaScript, running on the same document and window).

I need help fleshing this idea out a little more... any suggestions will help.

Answer 5

Create me a Brainf*** assembler

Write a way to convert "human readable" assembly (of any kind) to Brainf***. I.E specify a language "X" (which may already exist or may be your own invention), and create a way to map each valid program to a valid Brainf*** program. This is a popularity-contest so the most convenient assembler as evidenced by upvotes wins!

Answer 6

King of the golf course

Write a program that golfs Brainf*** programs. Similar to code-golf challenges on this site, you will be racing against the clock, and the byte count to maximize glory (reputation). Each program will be invoked with a series of command line arguments in this form

in out in out in out

Each program then has 1000 milliseconds to write a valid brainf*** program to botName.txt. This brainf*** program will take in a null terminated input from stdin and output the respective output according to the table. The code which writes the shortest programs as evidenced by the shortest of 5 runs (or more) will be crowned the winner with a green checkmark. Please note that my languages I support is limited and I may have to download the interpeter. I will have to disqualify non-free interpreters unless volunteers already possessing the interpereter/compiler are willing to help out.

---

Rules

1. You may assume that anywhere from 15-30 in and out pairs will be provided.
2. You may assume that inputs and outputs are valid english words from Random House Dictionary
3. You may assume a non wrapping brainf*** implementation with byte values for cells and a tape size of no less than 30k cells
4. The outputted bf programs may be of any length, but your submission may be no more than 10 kilobytes long (to prevent hardcoding)
5. Invalid submissions will result in immediate disqualification until a bug patch is uploaded

meta-golfbrainfck natural-language code-challenge

Answer 7

Expand constants in a Brainfuck program

code-golf metagolf kolmogorov-complexity code-generation brainfuck

Introduction

When golfing in Brainfuck, Fred can never remember the shortest way to write any given constant, and looking it up takes too much time! Luckily, Fred remembered that PPCG can help! In this challenge, you'll need to convert base-10 numerals their Brainfuck representations.

Challenge

Write a program or function that takes a string of Brainfuck code containing some numbers, like this:

72.>105.>33.

and transforms each number into one of its Brainfuck representations, giving (for example) this:

-[>+<-------]>-.>+[->-[<]>--]>.>>-[-[-<]>>+<]>.

Because Fred has not yet learned the secrets of Ctrl+C Ctrl+V, your code must be as small as possible to save Fred some valuable typing. Fred also wants to win code-golf contests with the output, so the code you generate must also be as small as possible.

Specification

• Standard loopholes are forbidden; in particular, you cannot scrape http://esolangs.org/wiki/Brainfuck_constants (or any other site for that matter).
• Your program or function may perform I/O through any of the default I/O methods.
• Assume a wrapping implementation with 1-byte cells (i.e. -. gives ÿ (255)).
• There will never be a number greater than 255 or less than 0 in the input (but you do have to handle 0 correctly!). Your program/function must handle all numbers 0-255 (inclusive).
• You may assume that there are as many temporary cells as necessary to the right of the pointer location (but not the left).
• You may assume that the cell where a number will go and all temporary cells are set to 0.
• When substituting a number, the pointer must end at the cell with the number. All temporary cells must be reset to 0.
• You may assume that there will never be any non-Brainfuck, non-digit characters in the input, and that the input will never be empty (i.e. the input will match /^[,\.\[\]+\-<>0-9]+$/).

Test Cases

The test cases given below are the output for a program/function using the shortest "wrapping" version of the constants at http://esolangs.org/wiki/Brainfuck_constants.

Input
Output
Brainfuck program's output

72.>105.>33.
-[>+<-------]>-.>+[->-[<]>--]>.>>-[-[-<]>>+<]>.
Hi!

255>10++>65>255<+[-<+]->[-+[->+]-<.+[-<+]->]
->++++++++++++>>+[+[<]>>+<+]>>-<+[-<+]->[-+[->+]-<.+[-<+]->]
AAAAAAAAAAAA

>0>48-->255<[>>86.[-]+[-<+]-<-]
>>-[>+<-----]>----->-<[>>-[>+<---]>+.[-]+[-<+]-<-]
VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV

>,[>,]<[<]>[.>]
>,[>,]<[<]>[.>]
(cat - outputs the input)

Scoring

Your score is your byte count plus the average length of your program/function's output for each number. For example, if a 30 byte program's output had an average length of 13.5, its score would be 30 + 13.5 = 43.5.

Helpful Hints

• http://esolangs.org/wiki/Brainfuck_constants

---

Sandbox Questions

Is it tagged correctly? Should this be code-challenge instead of code-golf metagolf?

Answer 8

Convert hexagonal coordinates to index

Your job is to, given the size of the hexagon and a pair of axial coordinates, return the index as if all the rows were laid out side by side.

Here's an example mapping for size 3:

(q,r), 3

       (0,0) (1,0) (2,0)
    (-1,1) (0,1) (1,1) (2,1)
(-2,2) (-1,2) (0,2) (1,2) (2,2)
   (-2,3) (-1,3) (0,3) (1,3)
      (-2,4) (-1,4) (0,4)

maps to

    00 01 02
  03 04 05 06
07 08 09 10 11
 12 13 14 15
  16 17 18

Here's the formula I found (could be improved):

i=index
s=size

i = q + sum( ( 2 * s - 0.5 - abs( x - s + 0.5 ) ) for x in 1..r )

Test cases (0-based indexing):

(q, r, s) -> i

(0, 0, 1)  -> 0
(0, 0, 50) -> 0
(0, 3, 3)  -> 14
(-3, 5, 4) -> 28
(5, 2, 12) -> 18

---

Meta notes:

• Should I include links to axial coordinates and centered hexagonal numbers?
  • Or, instead, should I explain axial coordinates better?
• Should I include the formula I came up with?
• More test cases, or are those fine?
• More exposition?
• I'm also planning to do a challenge the other way around, is that ok?

Answer 9

Rules

• Your program must take no input and print this text.
• You can have trailing newlines, and spaces after lines.
• You must not use a builtin or load the text for an external resource.

Score

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

Did you guess what was the text?

Answer 10

Point Triangulation

(title suggestions welcome)

code-golf geometry

Triangulation has been used for hundreds of years for land mapping and cartography, until the widespread proliferation of satellite positioning systems. Essentially, if you know two fixed points, A and B, you can uniquely describe a third point C by describing the angles BAC and ABC (the angle-side-angle postulate). The challenge here will be to solve for C.

Input

• Two rays (half-lines) of the form [(a point in x,y coordinates), (a direction in degrees or radians)] in any convenient format.
• The input angle will be relative to the Cartesian plane, i.e., an input of 0 degrees will have the ray parallel to the x axis and pointing toward x=+inf, and will follow traditional Euclidean convention that the angle increases counter-clockwise (e.g., 90 degrees is "straight up" toward y=+inf, 180 is "straight left" toward x=-inf, etc.).
• Please specify in your description the input format you're using.

Output

• The corresponding third x,y coordinate where the rays intersect, thus forming the triangle.
• If the input will not form a triangle, you can output an error, crash, output nothing, etc., so long as your code terminates. (META - is this too harsh? Should the input be guaranteed to form a triangle?)

Examples

[(1,0,90), (0,1,0)] -> (1,1)
[(1,0,90), (0,0,45)] -> (1,1)
[(1,0,90), (0,1,180)] -> undefined

additional examples forthcoming

related

Answer 11

Smallest Vigenere cypher executable

Brief

Impliment a Vigenere cypher program in your favourite language to create the smallest compiled program in any operating system.

For people unfamilar with a Vigenere cypher program, please visit the following link: https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher

Scoring

• Your score is the size in bytes of the folder that contains the main executable.

To find this, you must first compile your program. Secondly, delete any files unecessary to the running of your program. Finally, right-click on or list details by command line the folder (or equivalent standard action depending on operating system) containing the compiled executable and note the smallest of the listed size (e.g. size or size on disc in Windows) in bytes value.

• If dlls or similar are referenced, then their size in bytes must be added to the score.

• Interpreted languages may be used, but the size of a compatible interpreter (e.g. a web browser if using javascript) must be included when calculating the score.

Specific details

The program must accept 3 arguments:

• Argument 1 must be either 'e' or 'd', with e meaning encrypt and d meaning decrypt
• Argument 2 is the keyword string.
• Argument 3 is the main input string.
• If Argument 1 is 'e' then Argument 3 is the message to be encoded.
• If Argument 1 is 'd' then Argument 3 is the message to decoded.

The program must output the result only:

• If Argument 1 is 'e' then the result is the encoded string.
• If Argument 1 is 'd' then the result is the decoded string.

Rules

• The earliest dated post with the lowest score wins.
• In your answer post, post enough information so that others may repeat steps described to arrive at the same result. Presume that people reading your answer are fluent in your chosen language, but may not necesarilly understand any nifty tricks or exploits.
• Include your score in your answer post to let everyone know your score.
• You may post all your source-code if you like, but may also post only the parts that you feel are significant. There is no need to post automatically generated code, although if it is generated by a plugin then this should discussed. Failure to do so is considered cheating.
• Edits may not be made to answers. If you have made a mistake then delete and repost your answer anew.
• All edits and mistakes are considered cheating. Cheat answers are identified by members of the community leaving a comment. Cheat answers must be deleted, corrected and reposted.
• The community must use the comments to report cheating only. Be careful reporting cheats as a mistake may result in a good answer being deleted.
• Improvements should be listed as a new answer post.
• Take the competition seriously and be a good sport. Avoid ribbing, jokes or childish remarks.
• Have fun

Answer 12

N-ary Time

Decimal time is a concept of having days, hours, minutes, and seconds relate to each other by powers of 10:

N-ary time, which I made up, is having days, hours, minutes, and seconds relate to each other by powers of N.

Given an input N where minumum(2^31-1, [languages upper limit on integers])>N>1, output the value of an N-ary hour, N-ary minute and N-ary second, in seconds, using these rules: There are N^1 (10 in base-N) N-ary hours in a day, there are N^2 (100 in base-N) N-ary minutes in an N-ary hour, and there are N^2 (100 in base-N) N-ary seconds in an N-ary minute.

There are 86400 regular seconds in a day.

Input

Input must be an integer, inputted in anyway allowed

Output

Output consists of floats or integers that represent the amount of seconds in each N-ary unit within 0.5 seconds . Order is irrelevant.

Test cases

input-->output

2-->[43200.0, 10800.0, 2700.0] (or some other way of representing the data)

8-->10800 3 169 (numbers don't have to have specific order)

3-->28800.3200.356 (note that this might have the same character as decimal points, but it's still clear that they are three separate numbers)

Answer 13

Floating Point Error

Given a basic arithmetic problem, the division, multiplication, addition, or subtraction of two numbers (which are representable in a 32bit floating point), output the percent difference between the actual (mathematical) result and the nearest floating point value. The percent difference should be rounded to a whole number.

You may use either 32bit or 64bit floating point following the IEEE Standard for Floating-Point Arithmetic (IEEE 754).

The percent difference is calculated in the following manner:

100 * (Actual - Float) / Actual

You may round to a whole number in any of three ways, as long as you only use one method: (1) floor, (2) ceiling, (3) nearest.

Examples and Test Cases, yet to come.

Answer 14

Bomb Drops

code-golf [tag:???]

The Challenge

Your task is to create a program that simulates "dropping bombs" on a 2 dimensional array.

For example consider the following 2d array:

3 0 5 0 5
5 3 4 0 2
1 0 5 4 2
2 4 2 3 2
2 3 3 0 0

Dropping a bomb on a single cell decreases the value of that cell by 2 and the value of its direct neighbors (including diagonal neighbors) by 1, to a minimum of 0.

If we were to drop on a bomb on the cell corresponding to array[2][1] where the value is 4, or coords (2,1), then the new 2d array would look like so:

3 0 4 0 5
5 2 2 0 2
1 0 4 3 2
2 4 2 3 2
2 3 3 0 0

Input

Your input will be a two dimensional array of integers greater than or equal to zero, in whatever way you like.

You will then also take input that is a sequence of tuples, lists of size 2, or whatever else you please that corresponds to coordinate points. For example,

(2,1),(3,4),(0,0) or [2,1],[3,4],[0,0] or 2,1,3,4,0,0

For each of these points, you will simulate a bomb drop on that point. You do not need to worry about these coordinates being out of range of the 2d array.

Output

Output consists of a two-dimensional array, formatted the way you please.

Test Cases

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

# You can also take input in one pass, rather than 
# having the 2d array and the coordinates be seperate inputs:
>>> [[5, 2, 3, 0, 3], [4, 3, 5, 5, 5], [1, 3, 3, 3, 3], [0, 1, 2, 3, 1], [3, 1, 2, 2, 4]],[2,2],[0,1],[3,3]
# 5 2 3 0 3
# 4 3 5 5 5
# 1 3 3 3 3
# 0 1 2 3 1
# 3 1 2 2 4
4 1 3 0 3
2 1 4 4 5
0 1 0 1 2
0 0 0 0 0
3 1 1 1 3

Other info

Inspired from this question on StackOverflow.

---

This is my first challenge, I'm looking for any advice at all. I'm not sure what other tags to put aside from code golf. I'm probably missing a few basic rules etc too that I've forgotten about. All suggestions welcome.

Answer 15

Paint with all the colors of the RGB rainbow

^{Inspired by Images with all colors and American Gothic in the palette of Mona Lisa: Rearrange the pixels}

Given an input raster image, output a raster image where each pixel is a unique color, such that the sum of the absolute value of the sum of the differences of the RGB channel values for each pixel between the original image and the output image is minimized. In other words, that means, given an image O, find an image X such that every pixel is a different color, and (in pseudo-Python) the quantity sum(abs(O_pixel.RED - X_pixel.RED) + abs(O_pixel.GREEN - X_pixel.GREEN) + abs(O_pixel.BLUE - X_pixel.BLUE) for O_pixel,X_pixel in zip(O.pixels, X.pixels)) is minimized.

3-bit example

All images in this example are 4 pixels wide by 2 pixels high, magnified 40x to 160x80 so that they can be seen more easily.

Original image:

The palette:

The image using each color from the palette that is closest to the original (minimum sum 6):

Specifications

• All images will use 8-bit colors (3 bits in the red and green channels and 2 in the blue channel), and will be 16x16. Here is an image displaying the 8-bit color palette. Each color from this palette must be used exactly once in the output image.
• Submissions must complete for any of the test images in under 1 minute.
• If there are multiple optimal solutions, any one of them may be used.

Test cases

Original is on the left, expected output is on the right. All of these images are zoomed in; click the links to get the original-sized images.

Note that these two are the same, because the original image is already composed of unique pixels. Thus, the minimum sum is 0.

(more to come once my computer finishes generating them)

Answer 16

Convert Between American and British English Spellings

code-challenge test-battery natural-language

---

In this challenge, you will have to write two programs or functions. One will convert a list of words from their American English spelling to the British English equivalent, and the other to convert the other way. Here's that catch: you only have 300 bytes to do both!

The Challenge

You can find a gist here that contains a list of 1000 words. The file is formatted so each line is british-spelling(space)american-spelling. Therefore, there are only 500 words in total, each with 2 spellings. This file is for your convenience, and it was based on the list found here.

Your challenge is to write two programs or functions (has to be two programs or two functions, it can't be one program and one function). Both will take a single string as input and output a single string. The first program/function will take in British English words and output the American English spelling, and the second will take in American English words and output the British English spelling. Built-in functions or libraries that do this task are not allowed, nor are standard loopholes. You also cannot hard-code the list into your program. Your programs and functions have a shared 300 byte limit, i.e. length(program1)+length(program2)<=300. However, each program/function may be of different length.

Scoring

You will be scored based on how accurate your programs/functions were. Your score will be calculated based on the following formula:

Highest score wins. Ties are broken by shortest shared byte total.

---

SANDBOX NOTES

• I can't help but fell like I am missing something.
• Should I post the gist contents here, as well as a link to it?
• Is 300 bytes too generous, too litte, or is it fine?
-

Answer 17

How far is it?

I have no children myself but I understand they are more interested in the destination than the journey, so often ask how much of the journey is left. This might be a car trip, or it might be a demonstration of the Tower of Hanoi puzzle.

The original aim of the puzzle is to move all the disks from one pillar to another, but except for the smallest disk (which can be moved to any pillar at any time) the only disk you can move is the lowest numbered disk on the other two pillars.

Although there is a well-known optimal sequence from one pillar to another, each of the three moves will take you slightly nearer to finishing on a different pillar. (This partly explains why there are only two available moves when all the disks are already on the same pillar.) It's therefore possible to mistakenly take a detour towards another pillar yet correct yourself and finish at your desired pillar without retracing your steps. You should therefore not assume that the input position is from the optimal sequence.

The challenge is to write a program or function that accepts three sets (arrays, lists, strings, etc.) representing the sizes of the disks on each pillar and returns an integer giving the number of steps remaining to move all the disks to the first pillar. Examples:

[1, 2, 3] [0] [] -> 1
[2, 3] [0, 1] [] -> 3
[0, 1] [2] [3] -> 11
[0, 1, 2] [] [3] -> 15

Not only must your program return the shortest number of steps possible, but it must itself also be as short as possible.

Please indicate whether your input format requires the disks in a particular order.

Answer 18

The 9-hole GOLF challenge

Each of these challenges are fastest-code challenges to be judged by the GOLF CPU.

Hole 1: Prime Partitions

Hole 2: Sides of a Cuboid

Hole 3:

You are given the area of a polygon, and the number of edges of the polygon. You must find the minimal perimeter of the polygon. This challenge is more about implementing floating point/decimal numbers efficiently. Your answer must be accurate to at least 3 decimal places.

10, 5:    2.41088
7, 8:     1.20405
6700, 14: 20.9027

Hole 4:

You are given a number, A, and a base B. You must take the digits of A in base B and use each digit as the power of the digits before it. Assume that integer overflow is desired. For example,

125:  ((5)^2)^1     :25
3234: (((4)^3)^2)^3 :68719476736
18043:              :1
12540:              :0

Hole 5:

We define F(n) to be equal to the sum of all previous term's digits, and F(0) = 1. Given N, you must return the value of F(N). This sequence is A004307 on OEIS

0: 1
1: 1
2: 2
3: 4
4: 8
5: 16
6: 23
20: 137

Hole 6:

You must return the Nth decimal place of e

0:  2
1:  7
5:  8
25: 4

3 more holes (To come up with)

Do these holes look reasonable? Enjoyable? Confusing?

Answer 19

Remove first encountered elements from a list

Inspired by this question on Stackoverflow.

---

The task

Let's have two lists/arrays of integers: L1 and L2 of equal length. You need to remove from L2 the first occurrence of each number and from L1 the values on the corresponding positions. Then print/output the modified L1 and L2 (in that order). The separator between the elements of the list needs to be distinct from the separator between lists (both must not be numeric).

Since the lists can be long and have big numbers (but to your language's limits) your code needs to be as short as possible.

If (and only if) your language doesn't support lists, arrays or any similar structure, you can take the input as a string.

Example

L1 = [1 2 3 4 5 6 7 8 9]
L2 = [2 3 3 5 5 4 3 7 1]
Elements to remove from L2:
L2 = [2 3 3 5 5 4 3 7 1]
      ^ ^   ^   ^   ^ ^
Corresponding elements to remove from L1:
L1 = [1 2 3 4 5 6 7 8 9]
      ^ ^   ^   ^   ^ ^
Output result:
L1 = [3 5 7]
L2 = [3 5 3]

Test cases

Input -- Output
[1 2 3 4 5 6 7 8 9];[2 3 3 5 5 4 3 7 1] -- [3 5 7];[3 5 3]
[1 1 1];[1 2 3] -- [];[]
[2 2 2];[1 1 1] -- [2 2];[1 1]
[-1 0 2 123456];[-1 0 -1 0] -- [2 123456];[-1 0]
[1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40];[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1] -- [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40];[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]

code-golfarray-manipulation

Answer 20

Enumerate Irreducible Polynomials in GF(2)[X]

Meta:

• I noticed this is a duplicate of Find the XOR Primes
• Would it make it a non-dupe if we'd go from q=2 to q=3?
• Would it be more interesting for the general case, where the submissions have to take q(prime) and n

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code-golfmathbinarypolynomialsabstract-algebra

A polynomial over any finite field GF(q) of prime order q can be represented by an integral polynomial with coefficients in {0,1,2,...,q-1} ⊂ ℤ by the reduction modulo q. This allows us to easily enumerate all polynomials with coefficients in that field by using a polynomial p with coefficients in {0,1,2,...,q-1} ⊂ ℤ and evaluating it in q. So we map such a polynomial p to a nonnegative integer p(q). It is easy to show that this mapping is a bijection between the set of said polynomials and the nonnegative integers, when you consider one of those polynomials p(X) as an integer in base X.

Challenge

Let I be the set of irreducible polynomials with coefficients in GF(2), represented by integral polynomials with coefficients in {0,1}. Then enumerate all elements of {p(2) | p ∊ I} ⊂ ℤ in ascending order and let a(n) be the nth element. Given n your submission should return a(n). This is in fact A014580 in OEIS.

Examples

The irreducible polynomials in GF(2)[X] with a degree of at most 3 are: {p1(X)=X, p2(X)=1+X, p3(X)=1+X+X^2}. Substituting X by 2 results in p1(2)=2, p2(2)=3, p3(2)=7. So we see a(1) = 2, a(2) = 3, a(3)=7. Some more of those polynomials can be found on MathWorld.

Test cases

 n  a(n)
 1    2
 2    3
 3    7
 4   11
 5   13
 6   19
 7   25
20  103
34  203
35  211
50  355
53  369
54  375

Answer 21

Simulate Bibliomancy

In this challenge, you must take input as a string, and output a random word. Please note that you cannot simply take a random number and take the item of the list at that index: You will be simulating pages.

Also note that rather than your program picking from the page with eyes closed (which would bias towards larger words), it will generate a random number, and pick the word corresponding to that number

Pages will be some amount characters long, according to input (sandbox: I need help with how pages are distinct (are they assumed to be separate, or do pages need to have truncated length if a word is too long)). Every page has an equal chance of being picked (assume the PRNG is even), and every word on the page as an equal chance of being picked. In this way, a word from a grandiloquent page, with fewer words, is more likely to be chosen than a word from a page with many short words, and all the words on a page have an equal chance of being chosen. The sum of the chances of picking any word from one page is equal to the sum of the chances of picking any word from another page.

code-golf, this is that

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Of course, this still needs clarification. Halp sandbox

Answer 22

The grand golfed double radiation-hardened quine code-golf quine

Yep. It's quite a mouthful.

• Double radiation-hardened - removing any two characters still results in a valid quine.
• Quine - a program that outputs itself

Rules

• No reading from a file or from the web - that's cheating!
• Standard loopholes apply.
• File must be at least two characters long.

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

I've seen singly radiation hardened quines before. Now it's your job to make doubly radiation hardened ones.

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Please constructively criticize this challenge.

Answer 23

Time-Quine Time!

Your task is to write a quine (I know, I know, old stuff. But bear with me for a moment) which waits for a certain amount of time after the start of its execution, then prints its own source-code.

Rules:

• Standard Loopholes apply
• Your program must always halt for the same amount of time before printing its source code (System independent)

Input

• Your program should take no input

Output

• The programs exact source code (After the wait)

Scoring:

• This is code-golf, so shortest code wins, BUT:
• The time your program waits before printing is also taken into account. SO:
• Your score is equal to length of code (in bytes) / log(base 10)(time in seconds of wait)
• Code golf, so shortest code wins

P.S.: Please indicate in your answer how long your code will wait for

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All feedback is appreciated

Answer 24

Print this text in as few bytes as you can

**********
****  ****
***    ***
**      **
*        *
*        *
**      **
***    ***
****  ****
**********

kolmogorov-complexity

Answer 25

Play the centipede game

king-of-the-hill

(please note that I need to learn how to make a controller)

In this challenge, you must create a bot which plays the centipede game.

In the centipede game, there are two players, and two piles of coins. One pile is 1/4 the size of the other. Each turn, a player may choose to either: a) take the bigger pile of coins for himself, and push the smaller pile of coins over to the other player, or b) push both piles of coins to the other player. When the coins are pushed to the other player, the size of each of the pile of coins is doubled (in this way, the smaller pile increases to the current size of the big pile after two pushes).

In the original centipede game, there were 100 rounds (hence the name). However, in this game, there will be a random number of rounds. If the game ends without anyone defecting, the big pile will be evenly split between the bots.

The game is over when someone takes the pile instead of pushing it over, or the random amount of rounds are elapsed

I'm currently not entirely sure how to score it, but I know that a bot definitely cannot benefit from deliberately messing up the opponent (as in, it can't try to drag another players score down with it, even if that wouldn't be effective), other than the score it gains. something like Average score-(average score of games by other bots that weren't against the bot being scored), if that scoring method is not the inverse of what I'm trying to accomplish, but something formatted like that

Answer 26

Square pegs in round holes

code-golf geometry

Does a square peg fit through a round hole? Let's find out ...

Input

• Two 3-tuples, describing a circle and a square on the Cartesian coordinate plane.
• They're represented here by the form (x, y, r) and (X, Y, S).
• For both tuples, x and y are integers representing the center of the corresponding shape.
• The r and S will only be positive integers numbers, with r representative of the radius of the circular hole, while S is the length of the side of the square.
• The square is oriented parallel to the x and y axes -- i.e., the left and right sides of the square parallel the y axis, and the top and bottom sides of the square parallel the x axis.

(Meta: is this sufficient to describe the shapes?)

Output

• A truthy/falsey value, written to STDOUT or returned, indicating whether the square peg will fit through the round hole.
• The square can only fit through the round hole if the entirety of the square is completely enclosed in the circle -- no points of the square can intersect or lay outside the circle.
• Both objects are fixed at their corresponding centers (no rotating or translating about the origin allowed).
• Precision within usual 32-bit floating point is sufficient.

Rules

• Either a full program or a function are acceptable.
• The input numbers can be taken via any suitable format.
• Standard loopholes are forbidden.
• This is code-golf so all usual golfing rules apply, and the shortest code (in bytes) wins.

Examples

(x, y, r) (X, Y, S) -> result  # explanation
(1, 1, 1) (0, 0, 1) -> false   # square is offset from circle
(1, 1, 1) (1, 1, 1) -> true    # square easily fits in the circle
(1, 1, 1) (1, 1, 2) -> false   # some of the square is outside the circle

Answer 27

What number is this in the lowest possible base?

The challenge "What base is this number in" has an obvious extension:

Given a string that represents a number in an unknown base, determine the lowest possible base that number might be in, and taking the number in that base, output its base-10 representation. The string will only contain 0-9, a-z. If you like, you may choose to take uppercase letters instead of lowercase, but please specify this.

So, for example, if the input string is "01234", then the lowest possible base it could be a number in is 5. And in base-5, it represents:

01234_5 = 0 × 5^4 + 1 × 5^3 + 2 × 5^2 + 3 × 5^1 + 4 × 5^0 = (125 + 50 + 15 + 4)_10 = 194_10

So your program should output "194".

Your code must also work for base-1, aka "unary", where a number is represented by a string of zeros and its value is the number of digits. For example, 00000_1 = 5_10.

You can expect valid output to be anywhere from 0 to max_int.

You may take input and provide output in any reasonable format. Base-conversion built-ins are allowed (Sandbox q: Should there maybe be a bonus for not using them?), shortest answer in bytes is the winner!

Sample results:

    Input  | Base | Output
     1001  | 2    | 9
     34f9  | 16   | 13561
  0000000  | 1    | 7
  0000001  | 2    | 1
 codegolf  | 25   | 79234249915

Super-long example:

Input: 0123456789abcefghijklmnopqrstuvwxyz
Base: 36
Output (spaces for legibility, not required in actual program): 86 846 823 611 197 163 108 337 531 226 495 015 298 096 208 677 436 155

This output is roughly 180 bits, or 22.5 bytes, so may be out of range, but if your program can manage it then well done!

You may want to use baseconvert.com to help check your results.

Answer 28

How can I get To a RepDigit Rep?

Heavily inspired by this challenge

In the referenced challenge, Repdigits are defined as numbers composed of repeating single digits (1, 111, 88, 99999, etc). In this challenge, we will calculate the minimum number of Stack Exchange Q/A votes it takes to take a reputation to a repdigit.

A vote can either be:

• Question upvote (+5)
• Answer upvote (+10)
• Question/Answer downvote (-2)

Input: A single positive integer which represents a Stack Exchange reputation

Output: The minimum number of votes required to reach the nearest repdigit

Rules:

• Answer may be either program or function
• Input may be user input, read from a file, or function argument
• Output may have trialing spaces/new lines and should be printed/displayed to STDOUT or nearest equivalent. Alternatively, output may be the return value of a function
• Standard loopholes apply
• Answers should work theoretically for infinite reputation, however for practicality, answers only need to work up to 889,107 reputation (Jon Skeet's SO rep at time of posting)

Test Cases:

Reputation: 1   =>  Votes: 0 (input is already a repdigit)
Reputation: 10  =>  Votes: 1 (one downvote will result in 8 rep)
Reputation: 500 =>  Votes: 6 (5 answer upvotes and 1 question upvote resulting in 555 rep)

This is codegolf, shortest code in bytes wins

Answer 29

Strict Music Interval Describer

Given two notes, you might think you can combine Print the sizes of intervals inside of a piece of music to give you the number of semitones with Music Interval Solver to give you the name of the interval between them. Unfortunately doing this loses information. You might notice from the Music Interval Solver that different intervals can have the same number of semitones. In order to know which interval we should use, we need to refer back to the original note names.

The base name of an interval can always be determined from the inclusive number of note names, excluding accidentals, from the first note to the second. Note that intervals wrap after the octave, so that G# to C# is a fourth (G, A, B, C). For this question the octave numbers are not provided so you should assume that the interval will always be an ascending interval between a second and an octave.

To avoid having to refer to the linked questions, I will remind you that the notes themselves have differing numbers of semitones between them; E & F and B & C have one while the others have two. G to C is therefore 2 + 2 + 1 = 5 semitones.

You also need to take into account the accidentals; we'll use # and b for simplicity. They each alter the interval by 1 semitone; # increases it if used on the second note while b increases it if used on the first note. Naturally if both notes have the same accidental then they will cancel out.

An interval also has a modifier. My fourth above was in fact a perfect fourth, because the number of semitones was 5; the other possible perfect interval is a perfect fifth, which is 7 semitones. You can choose whether to use octave or perfect octave for 12 semitones.

Seconds, thirds, sixths and sevenths have minor and major intervals. The major intervals are 2, 4, 9 and 11 semitones; the minor intervals have one fewer.

Unlike the Music Interval Solver, if your interval does not match any of the intervals so far, you cannot simply change to a different base interval. Instead, you must augment or diminish your interval. For the purposes of this question any interval smaller than a minor or perfect interval is a diminished interval, and any interval larger than a major or perfect interval is an augmented interval.

Test cases:

Eb F# - augmented second
C# Eb - diminished third
G# C# - perfect fourth
F B - augmented fourth
B F - diminished fifth
Db B# - augmented sixth
A# Gb - diminished seventh
C# C - diminished octave

Input/output can be in any reasonable format (e.g. one string with a space separator, an array of two strings). This is code-golf, so the shortest code wins.

Answer 30

Limit a table

(this is in minimal form, and is in rough sandbox stage. refrain from voting at this stage. I will flesh it out at a later point in time.)

Given a CSV file containing two columns, and an integer N, format the table into multiple rows such that each column contains at most N rows, excluding the header. Like this, for N = 3:

Foo,Bar
hello,world
lorem,ipsum
doler,illum
asdf,fdasfa
qwerty,dvorak
tildes,graves
stuff,hello
limit,ipsum
a,b

Becomes:

Foo,Bar,Foo,Bar,Foo,Bar
hello,world,asdf,fdasfa,stuff,hello
lorem,ipsum,qwerty,dvorak,limit,ipsum
doler,illum,tildes,graves,a,b