Sandbox for Proposed Challenges

Question

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

Sandbox FAQ

Posting

To post to the sandbox, scroll to the bottom of this page and click "Answer This Question". Click "OK" when it asks if you really want to add another answer.

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

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

Discussion

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

• Parts of the challenge you found unclear
• Comments addressing specific points mentioned in the proposal
• Problems that could make the challenge uninteresting or unfit for the site

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

If you think one of your posts requires more feedback, but it's been ignored, you can ask for feedback in The Nineteenth Byte. It's not only allowed, but highly recommended! Be patient and try not to nag people though, you might have to ask multiple times.

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

Other

Search the sandbox / Browse your pending proposals

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Answer 1

Simulate World's smallest universal Turing machine

popularity-conteststringarray-manipulation

---

Goal:

to implement world smallest automata which was proved (though, not strictly) to be able to simulate any other universal Turing machine, Wolfram's 2-state 3-symbol Turing machine & prove your language's Turing-completeness.

Specification:

{{1, 2} -> {1, 1, -1}, {1, 1} -> {1, 2, -1}, {1, 0} -> {2, 1, 1}, {2, 2} -> {1, 0, 1}, {2, 1} -> {2, 2, 1}, {2, 0} -> {1, 2, -1}}

where this means {state, color} -> {state, color, offset}. (Colors of cells on the tape are sometimes instead thought of as "symbols" written to the tape.) Source

"Word" description:

Think of this machine as an array processing function. This array has a pointer accessible by function. Every cell in this array can store an integer from 0 upto 2. Array is infinite from both sides & pointer is pointing to somewhere in the middle of this array. function itself has 2 modes. in each mode, it works different than other. Let's call these 2 modes "A" & "B".

if in state "A" :

• if the value of the cell pointed by pointer is 0, change it to 1 & increase pointer & toggle state;

• if the value of the cell pointed by pointer is 1, change it to 2 & decrease pointer;

• if the value of the cell pointed by pointer is 2, change it to 1 & decrease pointer;

if in state "B" :

• if the value of the cell pointed by pointer is 0, change it to 2 & decrease pointer & toggle state;
• if the value of the cell pointed by pointer is 1, change it to 2 & increase pointer;
• if the value of the cell pointed by pointer is 2, change it to 0 & increase pointer & toggle state;

(Increasing the pointer moves it to right.)

Your program's array must be at least (2^16+1) and when it goes out of boundary, pointer must come back from other side. Size of array must be either dynamic or odd (Which at first, pointer is pointing to middle element of array).

I/O format

Though there aren't strict rules about input & output. Your program must at least get number of iterations as an input & output current pointer address (an integer, 0 at first, negetive if pointer gets decremented to subzero) & value of pointed cell along with a seprator (e.g. space) at every iteration. Though this is the minimal requirement.

Winning criteria(s)

There aren't many restrictions about challenge itself. But for wining, you'll need to get other users' votes. You can try to make an optimized system, or simulate it in a strange language, or have an strange design. But you mustn't add anything extra to machine itself, and must be able to produce the exact state of pointer and tape in a particular iteration.

This is a popularity-contest. Answers with highest votes will win.

Answer 2

The number 3 is cursed; avoid it

code-golf

_{Inspired from this}

It's well know that the number 3 may lead to weird bugs in a program. So your task is to write a program to remove every literal 3 (only the base 10 number; not a 3 in a string, a variable name, a longer number or with a different base) in a source code written in the language of your program by the floor of π.

But you can't have the character 3 anywhere in your source code.

You can't use a language without number literals.

Test cases (source language: Python)

print(3)
=>
import math
print(int(math.pi))

print("3 * 1 = %d" % 3)
=>
import math
print("3 * 1 = %d" % int(math.pi))

var1 = var2 = 33
var3 = 3 * var1 + var2 * 3
print("3 * %d + %d * 3 = %d" % var3)
=>
import math
var1 = var2 = 33
var3 = int(math.pi) * var1 + var2 * int(math.pi)
print("3 * %d + %d = %d" % var3)

print(0x3)
=>
print(0x3)

Since this is code-golf, the shortest answer in bytes win. Good luck!

Answer 3

Output a confusion matrix

A confusion matrix is a pretty typical thing to see in a machine learning paper. It is a matrix where each cell contains the number of instances of the class of the row that were classified as the class of the column.

For example, if we have two classes A and B, and 4 instances [A, A] (meaning that instance is of class A and was classified as A), [A, B], [B, B] and [B, B], then the resulting confusion matrix would be:

  A B
A 1 1
B   2

---

TODO: more details about the format, what happens if the name of the classes have different lengths, etc. etc.

Answer 4

Output a number tent

tags: code-golf ascii-art

---

Given an integer, output a number tent. (The number tent is just called as such.)

The input determines:

• whether the tent is upside down (negative) or right way up (positive),
• whether the entrance is on the left side (even) or the right side (odd), and
• the size of the tent (abs(input/2) http://mathurl.com/hwkkw3f.png with integer division).

---

For input -4:
________
\  /   /
 \/___/

Assume that the input will never be 1, 0 or -1.

TODO Clarify.

Your code should be as short as possible.

Answer 5

Find all paths in a matrix maze.

A maze is represented as a two-dimensional array of 0s and 1s. Zero indicates a closed door and one indicates an open door. An example representation of maze is given below.

0100
0010
1101

to avoid loops input square matrix should not contain a square of once like

111      11
101  or  11
111

Write an application either in Java,C,C++,Python,C# or Javascript. It takes as input a maze(mxn array) and prints out all the possible ways out.

• No database should be used.

• Yes...Way out is any edge containing 1.

• Enter from any edges of the maze

• Exit from any edges of the maze

• Should not enter and exit from the same door

• Move can be one unit distance either top/bottom/left/right/diagonal

For the above maze, one possible way out is: [0,1] -> [1,2] -> [2,3] i.e you start at [0,1] and then move to [1,2] and then to [2,3]. There are other possible ways as you can see.

Answer 6

Auto golf a string

popularity-contest metagolf

Your objective is to make a program (written in a language of your choice) that takes arbitrary strings as input and outputs a program in a constant target language that, when run, prints that string. The original program does not have to be golfed, but the output programs should be in some way optimal or nearly optimal.

Voters are encouraged to keep the following points in mind when voting:

1. How difficult is the target language to program in? Is it on par with languages such as Brainfuck and whitespace, or is it something trivial, like Python or Ruby?
2. How efficient is the golfer? That is, how does it compare to any existent auto string golfers? And how does it compare to hand-golfing?

---

Meta

Okay, so this isn't our usual type of challenge, but I think this could really turn out well. However, I think this is underspecified as it is, and would appreciate feedback.

Answer 7

Balanced use of the alphabet

Write a program that counts from 1 to 100 and back down and ends by the sentence "I finished counting":

1, 2, 3, ... 97, 98, 99, 100, 99, 98, 97, ... 3, 2, 1, I finished counting

The output can be of any kind: array, comma separated, line separated, ...

In order to do that, your code reviewer (who has a wierd OCD) won't accept code that doesn't contain the same amount of each letters of the alphabet.

He also doesn't accept code with no letter at all because, you know... letters are cool.

Scoring

Your score will be codeLength * (mostRepresentedLetter / leastRepresentedLetter).

Example of scoring

(Bad) code:

for(int i=1;i<=100;i++){abcdefghijklmnopqrstuvwxyz();}

Length: 39
Most represented letter: i (5 times)
Least represented letter: a (once)
Score: 39 * 5 / 1 = 195

NOTE: if a letter is not at all present, divding something by zero will make an inifinite score. As this is code-golf, it is not something you want.

Answer 8

Validate the traversals

Given inorder and preorder traversals of a binary tree, return a truthy or falsy value depending on whether they could be from the same tree.

Input can be strings of characters or arrays of characters or numbers, whatever is the most convenient. You can assume both inputs are the same length.

Examples:

inorder: A
preorder: A
result: true
example:
A

inorder: AB
preorder: AB
result: true
example:
A
 \
  B

inorder: AB
preorder: BA
result: true
example:
  B
 /
A

inorder: ABC
preorder: BCA
result: false
possible inorder trees:
    C   C   B   A   A
   /   /   / \   \   \
  B   A   A   C   C   B
 /     \         /     \
A       B       B       C
 CBA  CAB  BAC  ACB  ABC

This is code-golf, so the shortest solution wins.

Answer 9

Illuminati is Illuminati

This is a popularity contest inspired by a dedicated scratch programmer who made the program here: https://scratch.mit.edu/projects/117836320/. What the program does, is it takes in a string, and links the string to the Illuminati. This scratch program is especially popular because it demonstrates meta-satire on linking things to other things.

challenge

Your job is to more or less produce something of similar function and form to the one linked above.

Input:

Your program can take anything as an input, however, it has to be able to take something. My suggestion is a string.

Output:

Your program must output a series of links that make some sense, and eventually link your input to the illuminati.
The last output of your program must be some variation of [input] + " is Illuminati confirmed."

Scoring:

This is a popularity challenge. Your code isn't supposed to look great, or even execute well, so long as it has the most up votes. You must use a code that has a free compiler, and you must post your source code along with your program.

Tips and tricks:

This section will be updated, as people post suggestions in the comments.

• The Illuminati music in the background could add some spiff to your program. you can download it here: http://www.aiomp3.com/download.php?mp3=hAAlDoAtV7Y
• Unlike what the program listed above does, there are many more links to have done besides the number of letters an a string. try looking for anagrams, or similar words.

Answer 10

Translate an SVG path

An SVG path consists of a number of components. Each component begins with a letter, which may be upper case for an absolute position or lower case for a relative position. The component then has a variable number of parameters. Parameters may be separated by commas or spaces.

For the purposes of this question, you will not need to support the H, L or A commands. This means that each component accepts an even number of parameters, and that alternate parameters refer to the X and Y coordinates.

Given an SVG path and X and Y displacements, please output the translated path.

Input and output should be in any reasonable format, as long as you are consistent, i.e. both coordinates should be in the same format, or they can use a Point type, while the output path should be in the same format as the input path.

Please avoid floating-point errors e.g. adding 0.1 to 0.1 and getting 0.199996 like Inkscape does when I asked it to do this.

Example:

Input:
6.4
6.4
M 6.4 12.8 L 19.2 25.6 l 6.4 -6.4 z

Output:
M 12.8 19.2 L 25.6 32 l 6.4 -6.4 z

This is code-golf, so the shortest program wins.

Answer 11

Pointfree Generator -- this is a draft.... --

What is this?

From Wikipedia's page:

Tacit programming, also called point-free style, is a programming paradigm 
in which function definitions do not identify the arguments
(or "points") on which they operate

Challenge

In this challenge, you will have to generate Haskell code in pointfree style. You can provide an answer in any language of your choice as long as it generates Haskell code.

The functions to generate will be polynomial function of multiple variables with integer coefficients like : f : x,y,z -> x^8*y*z + 3*y + 12

for example, the function f : x -> x² + 3x can be written in pointfree Haskell like this (3*)>>=flip((+).(^2)) or (+3)>>=(*)

Input

The input is a list of list of coefficients and exponants : For example, the f : x,y,z -> x^8*y*z + 3*y + 12 function will be defined as [[1,8,1,1],[3,0,1],[12]]

Output

Restrictions

Haskell function/operators allowed are the following : (+),(-),(*),(.),(^),flip,(=<<),(>>=)

Hints

Testing

Scoring

Answer 12

Pitchers and Rivers

Credit for the idea for this challenge goes to Dan Garcia of UC Berkeley.

Many of you may have heard of any number of variations on the pitcher problem. For those who haven't, or need a refresher, the generalized form of the pitcher problem is as follows:

Given a list of pitchers of known size and a river filled with infinite water, how can you obtain a specific amount of water?

For a more specific example:

Given a 3-liter pitcher, a 7-liter pitcher, and a river, you can obtain exactly 2 liters as follows:

1. Fill the 3-liter pitcher.

2. Pour the 3-liter pitcher into the 7-liter pitcher.

3. Repeat steps 1 and 2 again twice.

4. If you didn't spill any extra water when filling the 7-liter pitcher the third time, the 3-liter pitcher will now contain 2 liters.

You cannot pour out part of the pitcher unless you can measure how much you poured out by filling something else up, e.g. another pitcher.

Your goal, now, is to determining which amounts of water you can get from your pitchers, given their sizes... but generalized to any number of pitchers.

Input

You will receive the pitcher sizes in any reasonable format. A (non-exhaustive) list of examples are:

1. A newline-separated list. 5\n13\n532

2. A Pythonic list. [3,7,13,22]

3. Prompt for input, like BF's .[>.]

You do not have to handle invalid input (e.g. negative sizes, empty lists)

Output

A list of obtainable (measurable) amounts of water, in any reasonable format. You may include 0, but you do not need to. You do not need to list the steps by which you obtain these quantities.

[3,5] -> [1,2,3,4,5,6,7,8]

[3,3] -> [3,6]

[4,6] -> [2,4,6,8,10]

[7, 5, 3, 2] -> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]

[30, 15, 5] -> [0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

[5,0] -> [0, 5]

[-1] -> Undefined behavior; sizes are always positive 

Reference solution in Pyth, barely golfed (100 bytes)

Answer 13

Code Golf: Convert to base 6 and back

If given a number, convert it to base 6. You can assume it is positive. You can get the number through any of these methods: STDIN, or ask for user input. If i has a 'o' at the end of it then assume the number is base 6 and convert it to a decimal number. Assume i is a string.

Example: Given i convert it. So if i = 12 then return 20. Given i convert it. so if i = 12o then return 8

Answer 14

Quine and Antiquine

code-golf quine

Your task is to make two different program, A and B. Both are nonempty proper quine. However, there is a restriction.

1. AB and BA produce no output.
2. CABD and CBAD will do the same thing as CD, where C and D are any (potentially empty) strings made up of copies of A and B. E.g. ABBABA and ABBBAA should behave identically (here, C = ABB and D = A).

The score is the sum of the length of A and B.

Example:

A program written in DJam:

program A :

abcd

program B :

efgh

Then, these output are sastified

abcdefgh
>> <empty output>
abcdabcdefgh
>> abcd
abcdabcdefghabcdefgh
>> abcd

Answer 15

Periodic Pillbox Problem code-golf

Pill-popping Patty is prescribed to take a particular pharmaceutical every P days. Presently, Phil has punked Patty's pill-box, punching holes in particular weekday's plastic pockets. Patty proceeds to plan pills P days apart whenever possible, but places pills in the preceding day's plastic pocket if the preferred pocket is punctured. Produce a pill planning chart presuming Patty popped her prior pill on the penultimate day of the previous week.

In case it's not clear, this is the kind of pill-box I am referring to.

---

Input:
The number P, followed by the 1 to 6 weekdays that Phil punctured. Beginning with Sunday(N) the weekdays are N M T W R F S. For instance 5MRF means Patty aims to wait 5 days after each pill, but cannot plan pills on Monday, Thursday, or Friday.

You can have the input with a single space after the number (e.g. 5 MRF) or with spaces after the number and each day (e.g. 5 M R F).

Process:
Given 5MRF Patty's first pill is taken on the first Wednesday (5 days from last Friday). Her second pill should be taken on the second Monday(5 days from the first Wednesday), but is moved up to the second Sunday because Monday is punctured. Her third pill should be taken on the second Friday(5 days from Sunday, not Monday), but is moved up to the second Wednesday because Friday and Thursday are both punctured. She continues in this manner indefinitely.

Note on the first week Patty's pillbox contains one pill on Wednesday, on the second and future weeks it contains pills on Sunday and Wednesday.

Output:
The pill planning chart shall indicate the state of Patty's pill-box each week, one week per line. Days she does not take her pill must have a dot ·. Days she takes her pill must have a capital X. The chart must stop as soon as the cycle occurs (i.e. in the fewest lines possible) with an arrow > pointing the first week in the cycle on the left. All weekdays must align in singly spaced columns with Sunday on the left.

Notes:
You may assume Phil was not malicious enough to puncture P consecutive days of the weeks, and that P is between 2 and 7 inclusive.

If Patty can't take her pill on the first Sunday, she takes it on the previous Saturday. Her pillbox was not damaged last week.

A cycle has occurred when pills are being taken on the same weekdays as in an earlier week.

Patty never waits more than P days to take her pill.

---

Testcase 1: 5MRF

  · · · X · · ·
> X · · X · · ·

Testcase 2: 5MR

> · · · X · · ·
  X · · · · X ·

Testcase 3: 5MF

  · · · X · · ·
> X · · · X · ·
  · · X · · · ·

Testcase 4: 6NTFS

  · · · · X · ·
> · · · X · · ·
  · X · · X · ·

---

A reference solution in C++ is provided here.

---

For The Sandbox...
First Challenge. Hooray! My biggest concern is whether or not there is anything with a similar process, I'm not sure if there is a generalization or a name for this sort of elimination thing. Barring that, is a good golfing question, can it be made a better golfing question, is clear what has to be done, etc. Really any advice is welcome.

Answer 16

Checkmate (aka the urinal problem) V2

inspired by Checkmate (aka the urinal problem)

given a non-negative integer n, assume there are n urinals.

also assume that you are not allowed to use an urinal when

• it is out of order.
• or a neighboring urinal is occupied.

If no urinal is available, the situation is considered checkmate.

Challenge:

Create a program or function that finds and prints (or returns, or yields) all possible checkmate combinations for n urinals.

Input: STDIN, command line argument or function argument

Output: Any output that makes the combinations clear is accepted.

---

TODO: add visual and test cases.

a thought:
This cries for string operations; how about a bonus for a calculational solution? Do bonuses suck?

Answer 17

Compute The anti-derivative of a non-constant function

Most of us know how anti derivatives work. They are basically the sums of infinite number of very small elements (or units).

The challenge here is to calculate anti derivative of a function (NON CONSTANT). using any programming language except the ones which calculate anti derivatives directly (Mathematica for instance).

Anti derivatives which have been calculated must be done by the usual summation method which is basically the definition of the integral. Summation of y.dx over some interval of x)

You basically have to find the anti derivative WITH limits i.e. definite integral of a non constant function in between two user specified limits

Answer 18

Download a file code-golf

Your boss wants you to make a comprehensive download utility. She uses Microsoft Bob and thinks shorter code is better code.

The Gist: In as few bytes as possible, given an input URL, output the file to stdout.

Input

• You will be given a fully qualified (w/ http/https) URL.
• Download link may redirect. Follow all redirects.
• Any non 2xx-3xx status code should be interpreted as an error. Exit with a status code of zero.
• Verify SSL certificates - exit with 0 if invalid

Misc

• Do not use a preexisting utility already designed for downloading files, such as wget. This is considered cheating.

Answer 19

Handwriting Recognition

code-golf image-processing

The MNIST dataset is a series of handwritten digits used as a standard testbed for machine learning, pattern recognition techniques. Each image is of a single digit, 0-9; as a 28x28 pixel grayscale matrix with values from 0-255.

The challenge is to create a classifier for MNIST that scores an Error Rate of less than [TBD] in the least number of bytes possible.

Your program must take a 28x28 2d array in whatever format is applicable for your language representing a single image. For example, the input for the first digit might be:

[[  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  3, 18, 18, 18,126,136,175, 26,166,255,247,127,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0, 30, 36, 94,154,170,253,253,253,253,253,225,172,253,242,195, 64,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0, 49,238,253,253,253,253,253,253,253,253,251, 93, 82, 82, 56, 39,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0, 18,219,253,253,253,253,253,198,182,247,241,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0, 80,156,107,253,253,205, 11,  0, 43,154,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0, 14,  1,154,253, 90,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,139,253,190,  2,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 11,190,253, 70,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 35,241,225,160,108,  1,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 81,240,253,253,119, 25,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 45,186,253,253,150, 27,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 16, 93,252,253,187,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,249,253,249, 64,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 46,130,183,253,253,207,  2,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 39,148,229,253,253,253,250,182,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 24,114,221,253,253,253,253,201, 78,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0, 23, 66,213,253,253,253,253,198, 81,  2,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0, 18,171,219,253,253,253,253,195, 80,  9,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0, 55,172,226,253,253,253,253,244,133, 11,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,136,253,253,253,212,135,132, 16,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
 [  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0]]

Conditions:

• This is code golf. The shortest piece of code that meets the criteria wins.
• The code must take a provided 28x28 input and attempt to classify it.
• Testing will take place on my computer at 12pm AEST on Saturday the . I will run each classifier over a set of 1000 images. To be considered, it must correctly classify [TBD] of them. If I can't get your code to run, it wont be counted, so help with loading the images in your language would be appreciated.
• Standard loopholes are not permitted.

Questions for Sandbox

• Overall thoughts on the challenge?
• Has anything been done like this before? Did it work?
• Any ideas on a good cutoff for the classifier? I was thinking around 60% correct. Though was going to have a go at it myself to see what I could reasonably achieve.
• Does the testing clause make sense? Is it reasonable? Should I put a limit on the languages?
• Since barrier to entry is a bit high (knowing how to get hold of the images, possibly some ML experience), is there anything extra I should do to make it easier to start the challenge.
• This is my first suggestion for a challenge, is there anything I'm missing?

Answer 20

Gif - Jif, Jif - Gif

code-golf

_{The point of this challenge is to (not) settle debate on the pronunciation of "gif"} http://38.media.tumblr.com/11bc6092d29c8c6840f9e10184ca03fd/tumblr_mlksz8SLjn1qz4h3co1_1280.gif

---

The pronunciation of gif is debated and while it's supposed to be (and should be) pronounced jif, it's still commonly disputed.

In this challenge you will be given a set of words that have a g or j, representing the sound that the word is pronounced with. You'll also get some text in which you have to fix the incorrect spellings of gif.

Because this is the internet and everyone always wrong. It's (not) common courtesy to correct them.

An example of a wrong pronunciation would be:

There was a gif of a mouse eating a burrito

The wrong spelling of gif? Unacceptable! This must be corrected immediately:

There was a jif (as in jar) of a mouse eating a burrito

---

Are we done? Nope, you're still wrong.

You're always wrong http://travelsummary.com/wp-content/uploads/2013/03/Im-Right-Youre-Wrong-e1363993322818.jpg

This must work the other way:

In the jif the cat wore a hat of a cat

This obvious misspelling must be fixed, we shall correct this to:

In the gif (as in graphic) the cat wore a hat of a cat

---

Rules

• You may assume all words that contain the letter g have the hard g sound (as in gravy) and all words that contain the letter j have the j sound (as in jam)
• Words will never have both g and j (Will add more specific rules later)
• Words must be picked at random each item with the same chance of being picked
• Words may be supplied through an array or the closest alternative for your language.
• Case must be preserved E.g. GiF -> JiF.
• You may write a program or a function

---

Examples

Input and output separated by a single line:

graphic, jar, jam, gram
I saw a jif of how to pronounce gif that showed gif is pronounced jif

I saw a gif (as in graphic) of how to pronounce jif (as in jar) that showed jif (as in jam) is pronounced gif (as in gram)

gravy, jeff
G is for gif, h is for jif, i is for gif, j if for jif

G is for jif (as in jeff), h is for gif (as in gravy), i is for jif (as in jeff), j is for gif (as in gravy)

Answer 21

Largest Number Given Digits and Operators

---

Challenge

Given a list of digits (0-9) and operators (+, -, /, *), output the largest number that can be formed using those digits and operators, as well as the mathematical formula used to create this number.

Rules

• All digits and operators must be used once and only once
• Parenthesis may be used in the outputted mathematical formula
• The outputted mathematical formula must be valid in an interactive Python shell (Note, this means ["--", "---", etc.], "//", "**", and ["++", "+++", etc.] are all valid operations that can be used in the output)
• Base 10 will be used
• For multiple different formulas that result in the same maximum number, output whichever one
• Input may contain any number of digits and operators
• Answers can be a function or program, and will be scored in bytes
• No loopholes or built-ins

Example I/O

Input: [1, 4, 3, *, +]
Output: +31*4
        124

Input: [1, 2, 0, '+']
Output: +210
        210

Answer 22

The one-looper ASCII box

Intro

I saw this one in one of my university programming textbooks as an "advanced" exercise and I thought it would fit very well here.

Task

Your program have to ask for an input number and draw a box with the size of the given number and a cross in it.
Example if the number is 7:

+-------+
|\     /|
| \   / |
|  \ /  |
|   X   |
|  / \  |
| /   \ |
|/     \|
+-------+

Example if the number is 10:

+----------+
|\        /|
| \      / |
|  \    /  |
|   \  /   |
|    \/    |
|    /\    |
|   /  \   |
|  /    \  |
| /      \ |
|/        \|
+----------+

The minimum width is 1 and it looks like this:

+-+
|X|
+-+

Notice that with an odd size, there is an X in the middle.

The hard part

In your program only one function is allowed (main) and in the main function there can be only one loop and that loop can only have one statement which can't be if. The shortest answer wins!

note: Sorry for the messy description but I had to translate it from my native language.

Answer 23

Interpret loose ranges code-golf

ListSharp is an interpreted programming language that has many features, one of those features is a 1 index based range creator that works like this:

You define a range as (INT) TO (INT) or just (INT) where both or the single int can go from min to max int32 value

Then you can use those ranges to extract elements of an array without fearing to overstep it's boundaries

---

therefore:

1 TO 5 generates: {1,2,3,4,5}

3 generates: {3}

Ranges can be added up using the AND operator

1 TO 5 AND 3 TO 6 generates: {1,2,3,4,5,3,4,5,6}

remember this works with negative numbers as well

3 TO -3 generates: {3,2,1,0,-1,-2,-3}

---

The challenge is the following:

Input

A character array and the previously defined range clause as a string

Output

The elements at the 1 index based locations of the range (non existing/negative indexes translate to an empty character)

---

How to win

Create the program with the shortest byte count

---

Test cases:

input array is:
{'H','e','l','l','o',' ','W','o','r','l','d'}

range clause:
"1 TO 3" => {'H','e','l'}
"5" => {'o'}
"-10 TO 10" => {'','','','','','','','','','','','H','e','l','l','o',' ','W','o','r','l'}
"0 AND 2 AND 4" => {'','e','l'}
"8 TO 3" => {'o','W','','o','l','l'}
"-300 AND 300" => {'',''}

Answer 24

Balanced Columns

I have a number of paragraphs of various heights which I would like to be distributed between some columns as evenly as possible. Here evenly means that you should minimise the total height of the tallest column, and then maximise the height of the shortest column, excluding empty columns.

The input will be an integer, representing the number of columns to be output, and an array of integers, representing the paragraph heights in lines. There is more than one way to represent the output; it could be an array (one for each column) of arrays of paragraphs, or it could be an array (one for each paragraph) of columns. (Please indicate whether your arrays are 0- or 1-based.) You may use any convenient format for (e.g. the number of columns as a command-line parameter and the array on STDIN) for I/O.

Because the paragraphs are double-spaced, there will be at least two lines in each paragraph, but if you prefer, your answer can take the double-spacing into account internally.

Within each column, paragraphs should be listed in ascending order, and the columns should be listed in ascending order of their first paragraph. Examples:

2, [2, 3, 4, 5, 6] -> [2, 3, 5], [4, 6] or [0, 0, 1, 0, 1]
3, [2, 3, 4, 5, 6] -> [2, 5], [3, 4], [6] or [0, 1, 1, 0, 2]
4, [2, 3, 4, 5, 6] -> [2, 3], [4], [5], [6] or [0, 0, 1, 2, 3]
5, [2, 3, 4, 5, 6] -> [2, 3], [4], [5], [6] or [0, 0, 1, 2, 3]

Note that in the last example the height could not be reduced by adding the extra column so in this case only four columns could be utilised.

Answer 25

No, this challenge is not this

Where is my error?

My compiler has broken down and now it is only showing the index of the character which the error is on.

In this challenge you will write a program to point to the given character.

Examples

Input:

if (goat == Downgoat) {
    print(Downgoat));
}

43

Output:

1 | if (goat == Downgoat) {
2 |     print(Downgoat));
  |                    ^
3 | }

Spec

TODO

Answer 26

Is this Rubik's Cube Solvable?

The challenge: find out if a rubik's cube configuration is solvable.

Takes input as a multidimensional array. An example for a solved cube would be

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

starting on the sides, going round, then top, then bottom. This input would give an output of 1, since it is solvable (very, very solvable). A (small) net of this solved cube would therefore be:

     _
 _ _|4|_
|0|1|2|3|
 ¯ ¯|5|¯
     ¯

The result of the program should be a truthy/falsey value, printed to STDOUT or similar. This is code-golf, so shortest answer in BYTES wins. Standard loopholes apply.

code-golf

Answer 27

Image Smoothing

Input into your program a black and white image. (png, jpg, etc)

Convert the image to a 2-d matrix of pixels. Where each index is the grayscale value of the image.

Take each index of the matrix and average the 8 pixels around it. Then replace that index with the average.

For example if you had:

120 80  60
20  10  30
40  100 05

If you were finding the average for 10, the result would be 56.875. Round to up to the nearest integer (57) and replace the index. The result of this iteration would be

120 80  60
20  57  30
40  100 05

If you are finding the average for a pixel on an edge then only take values that are valid. In the example above if you were finding the average for '20' You would only consider 112, 80, 57, 100, and 40, which is 79.4 rounded to 80.

You may start at any index of the graph but it must be in order, for example of you must go right - left, left - right, up - down, or down - up. You may not go something like randomly pick the indices to average.

Once the averaging is complete, convert the matrix back into a new image.

display the new image as the output of the program. (Or save it and add it in your solution). The result of this process should be a normal crisp looking image and the result would be a smoothed out image.

Please provide your code and start and end image (SFW please) and remember this is code-golf so the shortest code wins!

Good Luck and have fun!

Answer 28

code-golf internet

Implement BozoCrack

Designed to show why MD5 is a bad solution to password hashing, BozoCrack, for the uninitiated, is a rather simple and efficient method of cracking MD5 hashes. It doesn't brute force, use rainbow tables or indeed, any sort of math at all.

Instead, it finds the key by searching google for the hash and comparing the hash of each word in the results with the input.

Your task is simple: given at least one valid MD5 hash in a reasonable input format, find their source texts using Google and return or print to stdout the results.

In fact, you could probably arrive at the answer by finding the word in the page with the most occurrences -- you needn't use the results for a dictionary attack, but you must use Google.

The inputs can be given as an array of strings, as program arguments, space or otherwise delimited strings on standard input or in a file, etc -- whatever's easier for you, but make sure you specify in your answer how the input is taken.

Example inputs / outputs:

Input                            : Output
fcf1eed8596699624167416a1e7e122e : octopus
bed128365216c019988915ed3add75fb : passw0rd
d0763edaa9d9bd2a9516280e9044d885 : monkey
dfd8c10c1b9b58c8bf102225ae3be9eb : 12081977
ede6b50e7b5826fe48fc1f0fe772c48f : 1q2w3e4r5t6y

Of course, you may use your language's library function for computing the md5sum of a string -- but please, don't use any functions or libraries designed to solve exactly this task, e.g. Python's PyBozoCrack and the original BozoCrack.rb are disallowed.

In the unlikely event there are no results for a sum, print "NO RESULTS" to stdout instead.

Answer 29

AlphaGo..olf?

code-golf

(Slight paraphrased) Extract from Wikipedia:

AlphaGo is a computer program developed by Google DeepMind in London to play the board game Go and is the first computer Go program has beaten a 9-dan professional without handicaps.

In order to appreciate the Go art more, let's try to simulate what happens to the game when a move is made!

Input

The input will be:

1. a 4x4 board, (Here . denotes empty, o and x denotes different color of stones held by the 2 players respectively for illustration. Any standard input formats (2d array, array as sequence of alternative moves...) are welcomed as we like nice algorithms!)

2. a move to be made (Like A4, B2. You may also like to use 0-indexed and both numeric indices like (0,0)..(3,3)) For simplicity's sake, the move to be made is always with o (i.e. always the same color).

Output

The board after the move is made. Stones of the opposite color (i.e. x) will be taken away iff there are no more connected x that has at least 1 . in its 4-neighbor (Up, Down, Left, Right).

Examples

  Input | Move | Output
  ABCD  |      |
1 ....  | A1   | o...   (case 1: all stones remains on board)
2 ....  |      | ....
3 ..x.  |      | ..x.
4 ....  |      | ....
--------+------+--------
  ....  | B1   | .o..
  oxo.  |      | o.o.   (case 2: x taken away: the only . is taken)
  .ox.  |      | .ox.
  ....  |      | ....
--------+------+--------
  ..o.  | B1   | .oo.
  oxxo  |      | o..o   (case 3: >1 x taken away: the only . is taken)
  .oxo  |      | .o.o
  .xo.  |      | .xo.
--------+------+--------
  o.xo  | B1   | oo.o
  ..o.  |      | ..o.   (case 4: Edge case)
  ....  |      | ....
  ..o.  |      | ..o.
--------+------+--------
  x.o.  | B1   | .oo.
  ooxo  |      | ooxo   (case 5: Corner case)
  ...o  |      | ...o
  ..o.  |      | ..o.
--------+------+--------
  xxxx  | B2   | ....
  x.xx  |      | .o..   (case 6: Enclosed by Board case)
  xxxx  |      | ....
  xxxx  |      | ....
--------+------+--------
  .oxx  | C2   | .o..
  ox.x  |      | o.o.   (case 7: Enclosed by o case)
  oxxx  |      | o...
  .ooo  |      | .ooo
--------+------+--------
  .xo.  | A1   | o.o.
  xo..  |      | .o..   (case 8: taking multiple groups case)
  o...  |      | o...
  ....  |      | ....
--------+------+--------

Rules

1. This is code-golf thus the shortest code wins.
2. Please kindly provide explanations and ways to test the solutions!
3. The Input board can be assumed to be correct: there will be neither x that without a connected x with ., nor a group of o surrounded by x without .
4. The Input move can be assumed to be legitimate: either it won't be a position surrounded by x, or it must take away some x to free . for the o to live. (ref. case 6, 7, 8)
5. The output must be the board, it may or may not be in the same format as the input (if you take input as 2 arrays of o and x positions, say). Output that only shows the stones that are taken away after the move is made will not be accepted.
6. Again, feel free to play with the standard input formats. Hope to see interesting 1 and 0 playing Go instead of o and x :P

Meta Questions

1. I don't know if this may be too hard. Would it be better if I allow golfers to fail some test cases and get penalty instead?
2. Should I stick with a 4x4 board or I can award minus scores if the solution can work with a 19x19 board?
3. If it is a yes to any of the above questions, which should be the number for the penalty / award?

Thanks!

Answer 30

Categorize the asymptotic behavior of a consumer/producer system

Given two functions P(t) and C(t), output the correct category for the behavior of P(t)-C(t) as t goes to positive infinity:

1. Ideal: P(t)-C(t) goes to 0.
2. Stable: P(t)-C(t) oscillates, with the time spent as a positive value equal to the time spent as a negative value within a single oscillation period.
3. Hungry: P(t)-C(t) either converges to a negative value, or oscillates, with more negative values than positive values in one oscillation period.
4. Starved: P(t)-C(t) diverges, approaching negative infinity.
5. Saturated: P(t)-C(t) either converges to a positive value, or oscillates, with more positive values than negative values in one oscillation period.
6. Oversaturated: P(t)-C(t) diverges, approaching positive infinity.

Rules

• The expected output will always be one of the above cases - you don't have to worry about other cases
• P(t) and C(t) will always be real-valued continuous functions that only consist of the following operations: addition, subtraction, multiplication, division, exponentiation (for constants a and b and parameter t, a^b, t^a, and a^t are all allowed), principal roots (real roots, only when they exist, and only the positive root when there are 2 real roots), logarithms, and basic trigonometric functions (sine and cosine of arbitrary values, and tangent for values that are not odd multiples of pi/2)
• Input may be in any reasonably format (string, function object/pointer, mathematical function object, etc.)
• You may use any unambiguous set of 6 values for output (like [1, 2, 3, 4, 5, 6], [0, 1, 2, 3, 4, 5], [Ideal, Stable, Hungry, Starved, Saturated, Oversaturated], or [0, ~, -, -∞, +, +∞])

Test Cases

TBD

Sandbox Notes

• Are the definitions and rules clear?
• Are there any I/O methods that should be explicitly allowed or forbidden that aren't covered by the current rules?