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.

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Answer 1

Extension of MIME-Type

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

---

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

Cases to handle:

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

Cases you don't have to touch:

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

I & O

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

Winning

• This is code-golf kolmogorolofvlfoao-complexity, lowest byte-count wins.

Answer 2

I have a large collection of fine art. My toddler is learning to use scissors and glue; lately she has started playing with my art collection. Fortunately she is really quite good with the scissors and cuts things up into perfect squares. She then uses glue to randomly tile the cut-up squares back into a new piece of art. For example, she reinterpreted my Mona Lisa (which wikipedia kindly hosts for me) as follows:

The following python script simulates what my toddler has done:

#!/usr/bin/python

import sys
import random
from PIL import Image

origname = sys.argv[1]

im = Image.open(origname)
width, height = im.size
width = (int(width + 99) / 100) * 100
height = (int(height + 99) / 100) * 100

im = im.crop((0, 0, width, height))

im2 = Image.new("RGB", (width, height), "black")

blocks = []
for x in range(width / 100):
    for y in range(height / 100):
        blocks.append(im.crop((x * 100, y * 100, (x + 1) * 100, (y + 1) * 100)))

random.shuffle(blocks)



im2.save("shuf" + origname)

_{Please excuse python skills - I'm still learning, but was happy to see how quick and easy it was to write this script. Polite code-reviews will be graciously accepted ;-)}

It does the following:

• loads the image whose file name was given as a command-line parameter
• pads that image with black pixels such that the width and height are exactly divisible by 100
• divides the image into 100x100 pixel blocks
• randomly shuffles the blocks
• reassembles the randomly arranged blocks back into a new image with the same size attributes as the (padded) original
• saves the new image using the original filename prefixed with shuf

---

Your task is to write a program that takes the output of this script, analyses the edges of each 100x100 block and reassembles them back to the original picture.

Input:

• an image filename. This may be passed at the commandline, via STDIN or even hard-coded, whichever is most convenient.

Output:

• either output the a singular rearranged image to a differnent file, or display the singular rearranged output to the screen.

Input and output specs are intended to be lenient here, as filename-parsing is a non-goal of this code-golf question.

Other rules

• The program must be able to correctly reassemble any random arrangement of the wikipedia Mona Lisa by the python script. Hard-coding of block transformations of the example image above is strictly not allowed.

• It is understood that for some degenerate cases (e.g. chequerboard of 100x100) blocks it is impossible to correctly rearrange the image. In those cases it is acceptable to produce incorrect/undefined output. However I think in general for photo images and almost all "famous" artworks, reassembly should be possible. Works by Mark Rothko are a possible exception.

• Common image manipulation libraries may be used (e.g. Python's PIL), but any APIs expressly designed for this purpose are strictly banned.

• Standard “loopholes” which are no longer funny

---

Now my toddler got a hold of The Scream. This is the result that needs to be fixed:

Special thanks to Digital Trauma!

He wrote the original challenge and gave it up original post here

META:

I need to update the images and the script to not have rotations and to not have black bars. Any ideas?

Answer 3

Make some arrays

A recent post on The Daily WTF concerned the creation of four two-dimensional arrays of height n. Please write a function to create these arrays for me. Here is an example for n=4:

[[1] [[1 0 0] [[0] [[0 0 0]
 [0]  [0 1 0]  [0]  [1 0 0]
 [0]  [0 0 1]  [0]  [0 1 0]
 [0]] [0 0 0]] [1]] [0 0 1]]

Rules:

• All four arrays must be two-dimensional. Arrays which have been flattened in any way are not acceptable.
• You can write separate functions for each array, in which case your score is the total of the scores for each function.
• Your functions can call each other, provided you include the name in your score. Otherwise unnamed functions are acceptable.
• Rather than returning the array(s), you can be passed them in as an input parameter (e.g. using int** in C).
• If your language has a builtin for inputting arbitrary data structures, then you can write a full program that outputs using the input format that the builtin would recognise.
• Alternatively, you can write a full program that outputs source code for the arrays in your language.
• All standard loopholes are banned.
• This is code-golf, so the shortest function wins.

Answer 4

Parse a 4-dimensional array

A 2D array is fairly easy to represent in ASCII art, something like this:

1  2
6 24

One approach for a 3D array is to have a number of 2D arrays, with an extra blank line between each array:

1  2
6 24

1  2
4  8

Things get a little more complicated for 4D arrays though. The best you can do is to arrange a number of 3D arrays side-by-side, but with at least two spaces between each array:

1  2   1  2
6 24   3  4

1  2   1  4
4  8  27 64

So that I don't have to ban full programs, the challenge will be to input 4 (numeric) indices along with a 4D array which will be as some sort of string in the above format, and output the (numeric) 4D array element at those indices. For example, if the 1-indexed indices were 1, 2, 1, 2 then the result would be 4. Rules:

• You must at a minimum support integers from 0 to 255, written in decimal.
• The array will not be ragged, but you will not be given the size of the array. Any of the dimensions may be 1, so 0 0 0 0 0 is a valid input in 0-based indexing.
• Numbers in the array will be consistently justified (please state whether you support left or right, or decimal justification if you support floating-point numbers), but the output must not contain any whitespace except for an optional trailing newline.
• You may choose 0 or 1-based indexing.
• You can choose row-major format instead of column-major format, as long as both outer and inner arrays have the same format. The first two indices will however always refer to the outer array and the last two indices to the inner array indexed by the first two indices.
• You can assume that the indices will always be valid.
• All standard loopholes are banned.
• This is code-golf, so the shortest program or function wins.

Answer 5

code-golf

Generating strings of Rs and spaces

If a task is to make a string of 16 characters using 2 different characters, it can be done in 2^16=65536 ways. Let's generate them all!

Write a program or function which takes a number in range [0, 65535] as input and outputs a string of 16 characters consisting of R and  (space). One number corresponds to one string and must generate the same string each time the code is run.

Example

Suppose that a program/function takes a binary representation of the number and replaces zeros with spaces and ones with Rs to make the string. The conversion from input to output will look as follows:

0     -> "                "
1     -> "               R"
2     -> "              R "
3     -> "              RR"
...
65532 -> "RRRRRRRRRRRRRR  "
65533 -> "RRRRRRRRRRRRRR R"
65534 -> "RRRRRRRRRRRRRRR "
65535 -> "RRRRRRRRRRRRRRRR"

Sandbox notes

• This challenge probably needs a better name. If you have an idea, please mention it.
• I know that this challenge will be boring if making the string from binary representation is the shortest way in all languages. I hope that this isn't the case.

Answer 6

Boxes

N boxes are lined up in a sequence (1 ≤ N ≤ 20). You have A red balls and B blue balls (0 ≤ A ≤ 15, 0 ≤ B ≤ 15). The red balls (and the blue ones) are exactly the same. You can place the balls in the boxes. It is allowed to put in a box, balls of the two kinds, or only from one kind. You can also leave some of the boxes empty. It's not necessary to place all the balls in the boxes.

challenge!

Write a program, which finds the number of different ways to place the balls in the boxes in the described way.

Input

Input contains one line with three integers N, A and B separated by space.

Output

The result of your program must be an integer written on the only line of output.

Sample I/O

input

2 1 1

output

9

Answer 7

Simplify ordinal expression

WIP.

Answer 8

Split the atom

Input: 0 <= X <= 2³² - 1

Output: List of numbers in decimal, after recursive splitting in binary format.

Explanation:

Example 1:

Input: 255

Current Output is 255.

Binary representation of 255 is 1111 1111. Splitting it, we get 1111 and 1111, which in decimal are 15 and 15.

Continuing the Output, we will have 255 15 15.

Now the numbers 15 and 15 will serve as inputs and these numbers are to be split.

Continuing the Output, we will have 255 15 15 3 3 3 3.

Continuing the logic, final Output will be 255 15 15 3 3 3 3 1 1 1 1 1 1 1 1 . And since 1 can no longer be split, the output stops.

Example 2:

Input: 225

Current Output is 225.

Binary representation of 225 is 1110 0001. Splitting it, we get 1110 and 0001, which in decimal are 14 and 1.

Continuing the Output, we will have 225 14 1.

Now the numbers 14 and 1 will serve as inputs and these numbers are to be split.

Since 1 is no longer split-able, the Output will be 225 14 1 3 2.

Final Output will be 225 14 1 3 2 1 1 1 0.

Example 3:

Input: 32

Output: 32 4 0 1 0.

---

Conditions:

1. If the number of binary digits are odd, the first number will have one fewer binary digit than the next one. Example, 20 (10100) will be split as 10 and 100, with decimal output being 2 and 4.
2. Standard loophole rules apply.
3. 0s and 1s do not propagate further.
4. Program crashing for trying to display too many numbers is a valid exit condition.

Answer 9

Pi - The Movie!

Introduction

So we've had the musical version The Sound of Pi, now its time for the movie.

Challenge

Your challenge is to write a full program or function that outputs an animated version of pi to 100 decimal places.

For your convenience, here's Pi to 100 decimal places

3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679

Input and Output

Input: No input required

Output: A single gif file

Rules

• Only one digit or decimal point should be shown at a time
• Each digit or decimal point should be shown for for between 0.25 and 1.5 seconds (your choice).
• The font should be clearly visible (different colour to background)
• The characters should be at least 100 pixels high and have at least a 1 pixel boarder
• You can use built in values of pi as long as they're correct to 100 dp
• Standard loopholes apply
• This is code-golf, so the submission with the least amount of bytes wins!

---

Sandbox questions

• Is the time constraint realistic?
• What tags should I use?

Answer 10

Introduction

Wardialing was a very interesting way to try to hack people back in the '80s and '90s. When everyone used dial-up, people would dial huge amounts of numbers to search for BBS's, computers, or fax machines. If it was answered by a human or answering machine, it hung up and forgot the number. If it was answered by a modem or a fax machine, it would make note of the number.

Challenge

Your job is to make a URL wardialer. Something that tests and checks if it's a valid website from one letter of the alphabet.

Constraints

• Program must take user input. This input has to be a letter of the alphabet, no numbers. Just one letter of the alphabet and form multiple URLs that start with the letter.
• Standard loopholes apply.
• You must make 8 URLs from 1 letter, and test to see if it is a valid site.
• If you hit an error (not a response code), instead of leaving it blank, go ahead and return a 404
• If you hit a redirect (3xx), return a 200 instead.
• You may output the results in any reasonable format, as long as it includes the website name, status codes for all the websites and the redirects
• This is Code Golf, so shortest amount of bytes wins.

What counts as a URL for this challenge?

http://{domain-name}.{com or net or org}

For this challenge, the domain name is should only be 4 letters long, no more, no less.

What should I test?

For each 4 letter domain name, test it against three top-level domains (.com, .net, .org). Record all the response codes from each URL, remember from the constraints that any (3xx) should return 200 and be recorded as a redirect in the output and any error getting to the website should result in a 404.

Input

a

Output

+---------+------+------+------+------------+
| Website | .com | .net | .org | Redirects? |
+---------+------+------+------+------------+
| ajoe    | 200  | 200  | 200  | .com, .net |
+---------+------+------+------+------------+
| aqiz    | 200  | 404  | 404  | no         |
+---------+------+------+------+------------+
| amnx    | 200  | 503  | 404  | .com       |
+---------+------+------+------+------------+
| abcd    | 200  | 404  | 200  | .com       |
+---------+------+------+------+------------+
| ajmx    | 200  | 503  | 404  | no         |
+---------+------+------+------+------------+
| aole    | 200  | 200  | 200  | .com       |
+---------+------+------+------+------------+
| apop    | 404  | 200  | 200  | .net       |
+---------+------+------+------+------------+
| akkk    | 200  | 200  | 200  | .com       |
+---------+------+------+------+------------+

Answer 11

Program Equilibrium Iterated Prisoner's Dilemma Tournament

This is an iterated prisoners dilemma tournament. You are to make a bot that plays the prisoners dilemma against the other contestants, but with a twist- you can perfectly simulate your opponent!

Iterated Prisoner's Dilemma

The prisoner's dilemma is a two-player game in which players can choose to either "Cooperate" or "Defect" against their opponent. The payoff matrix for the prisoner's dilemma looks like this:

                           Player 2
                       C              D

                 ------------------------------
                |              |               |
            C   |    (3, 3)    |    (0, 5)     |
                |              |               |
Player 1        |------------------------------|
                |              |               |
            D   |    (5, 0)    |    (1, 1)     |
                |              |               |
                 ------------------------------

In the iterated prisoner's dilemma, multiple rounds are played in succession, and players can use their knowledge of the previous rounds when making a decision.

The twist

Bots are also allowed to run their opponent and examine the output before making a move. This allows for significantly more complex strategies in which bots can simulate their opponents to determine if it is safe to cooperate with them, as well as attempt to exploit less sophisticated players.

Simulation

There will be a program available in the path called simulate that you can use to simulate what your opponent would do against you

Usage:

simulate [instruction to your own bot] [fake history to the opponent]

Example:

simulate cooperate 00 10 01 11 01 10

All arguments are optional, and you may also use underscore _ for no argument. If you do not explicitly state the history, the real history will be used.

Example output from the simulate program:

01

The first number is you, the second is your opponent. 0 means defect, 1 means cooperate.

The instruction

It wouldn't be much use to simulate what your opponent would do against you, because he'd probably simulate you right back, and then you'd be stuck in an infinite loop.
The instruction is your way to simulate what the opponent would do against another agent. You could for instance have a cooperate instruction that causes your bot to cooperate mindlessly, to see what the opponent would do if you were to cooperate.

Input

Your program will be given the following input at the beginning of each round:

Instruction (if any)
Your score
Your opponents score
Current round number
Complete history of past interactions with this bot. Space separated: the first number is you, the second is your opponent

Example:

cooperative
5
2
3
00 10

Output

0 for defect or 1 for cooperate, with any number of leading characters. Trailing characters (including 0 or 1's) will be ignored.

Example:

1

The tournament

The tournament will be round-robin elimination: Each bot will play one match against all other bots, where a match consists of 100 rounds of the prisoner's dilemma. At the end of the round-robin round, the lower-scoring half of the tournament pool will be eliminated. This process will be repeated until only one bot remains, or there is a tie.

Rules

• Your program has to run on Linux. Please provide a brief description of how to run your program if possible
• Your program has to give an answer within 5 seconds. Failing to do so will be interpreted as defect.
• Your program may not perform multiple simulations at the same time
• You may only enter a single bot, this is to prevent people from entering multiple bots that cooperate
• You may not read or write any files. If this is required by your language, please state so in your answer.
• You may not in any way store state between rounds. This is to prevent bots from figuring out whether they are being simulated.
• If you exploit another loophole to figure out whether you are being simulated, you will be disqualified. Guessing (or strategical testing) is obviously allowed

About the host computer

Arch Linux 4.10.13-1
Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz, 4 cores
16 GB RAM
I will disconnect from the internet while running the tournament

Disclosure

I got the idea as well as some of the text from this Github repository. I have not directly asked the author for permission to use the challenge, but he said that "if you want to run this tournament on your own, you are more than welcome to" in a blogpost.

Leaderboard

I will update this periodically whenever new bots enter.

Meta

How do I best discourage/prevent players from intentionally using every bit of their time limit to sabotage other players trying to simulate them? I am thinking random time limits and/or penalties

Answer 12

Identify the variable case

Your task is to write a function which determines which casing convention a provided variable name belongs to:

• camelCase
• kebab-case
• Train-Case
• snake_case
• SCREAMING_SNAKE_CASE
• PascalCase
• Ada_Case (not a real term, but apparently the standard casing used in Ada)

Your function should return one of the above strings, either exactly as above, or as spaced title-case: "Train case", "Screaming snake case".

Casings that include - or _ may include leading or trailing -s or _s (eg, __MY_SNAKE__ or -webkit-kebab).

Multiple consecutive upper case letters are allowed in mixed casings, as long as they follow a lower case letter (MyXMLDocument, This-CSS-Crap).

Where an input fits multiple schemes (eg, F or foo), you may return any valid classification.

If an input does not fit one of the above schemes (eg stu-pid_case), you must return something different. You may also throw an error.

The input string is guaranteed to be at least one character, and begin with a character matching /[a-zA-Z_-]/. Every other character will match /[a-zA-Z0-9$-]/

This is code-golf, so shortest length in bytes wins. Standard loopholes forbidden. Standard input and output methods.

Test cases

myFunkyVariable => camelCase
no-op => kebab-case
TEST2 => SCREAMING_SNAKE_CASE
__c => snake_case
XML-Madness => Error
Get_Input => Ada_Case
i => camelCase (or snake_case)
char2int_factory => snake_case

Answer 13

21 = (1 + 3 + 5 + 7 + 9) - (1 + 3)

Sandbox question:
Is this different enough from the original challenge?

---

Background

• This is a sequel to my previous challenge, but this time with a slightly more interesting practical application (the factorization of the input).

• It is based on 1) the fact that any odd integer n can be expressed as the difference of two squares a² - b² and 2) the well known formula:

  

The task

You're given a positive odd integer n. Your task is to determine how many iterations of the following algorithm need to be processed to reach n.

• Initialization: find the highest integer k such that k² ≤ n. Build the list L = [ 1, 3, 5, ..., 2k-1 ].
• Iteration:
  • Step #1: If the sum of the terms of L equals n, stop here.
  • Step #2: Increment k and append 2k-1 to L.
  • Step #3: While the sum of the terms of L is greater than n, remove the first term from the list. Go on with step #1.

All iterations (either full or partial) must be counted. In other words, you must return the number of times step #1 was executed.

Example #1

This is a trivial example for the perfect square n = 9:

• Initialization: k = 3 because 3² ≤ 9 < 4², which leads to L = [ 1, 3, 5 ].
• Step #1: 1 + 3 + 5 = 9. We're done.

We went through one iteration. So the expected result is 1.

Example #2

Here is what we get for n = 21:

• Initialization: k = 4 because 4² ≤ 21 < 5², which leads to L = [ 1, 3, 5, 7 ].
• Step #1: 1 + 3 + 5 + 7 = 16, which does not equal n.
• Step #2: We increment k and we add 2k + 1 = 2 x 5 - 1 = 9 to the list: L = [ 1, 3, 5, 7, 9 ].
• Step #3: We remove the first term from the list: L = [ 3, 5, 7, 9 ]. The sum of the terms is now 24, which is still greater than n. So we remove another term: L = [ 5, 7, 9 ].
• Step #1 : 5 + 7 + 9 = 21. We're done.

We went through two iterations. So the expected result is 2.

Example #3

Below is a summary of all steps for a slightly more complex example with n = 145.

Initialization: k = 12 because 12² ≤ 145 < 13².

Iteration | Step | k  | L                                 | Sum
----------+------+----+-----------------------------------+----
    1     |  1   | 12 | 1,3,5,7,9,11,13,15,17,19,21,23    | 144
          |  2   | 13 | 1,3,5,7,9,11,13,15,17,19,21,23,25 | 169
          |  3   | 13 | 11,13,15,17,19,21,23,25           | 144
----------+------+----+-----------------------------------+----
    2     |  1   | 13 | 11,13,15,17,19,21,23,25           | 144
          |  2   | 14 | 11,13,15,17,19,21,23,25,27        | 171
          |  3   | 14 | 17,19,21,23,25,27                 | 132
----------+------+----+-----------------------------------+----
    3     |  1   | 14 | 17,19,21,23,25,27                 | 132
          |  2   | 15 | 17,19,21,23,25,27,29              | 161
          |  3   | 15 | 19,21,23,25,27,29                 | 144
----------+------+----+-----------------------------------+----
    4     |  1   | 15 | 19,21,23,25,27,29                 | 144
          |  2   | 16 | 19,21,23,25,27,29,31              | 175
          |  3   | 16 | 23,25,27,29,31                    | 135
----------+------+----+-----------------------------------+----
    5     |  1   | 16 | 23,25,27,29,31                    | 135
          |  2   | 17 | 23,25,27,29,31,33                 | 168
          |  3   | 17 | 25,27,29,31,33                    | 145
----------+------+----+-----------------------------------+----
    6     |  1   | 17 | 25,27,29,31,33                    | 145

We went through 6 iterations. So the expected result is 6.

Factorization of the input

This paragraph is for illustration purposes only. It describes how the factorization of the input can be deduced from the result of the algorithm.

Factorization of 21:

• 21 = 5 + 7 + 9 = (1 + 3 + 5 + 7 + 9) - (1 + 3)
• 21 = 5² - 2²
• 21 = (5 + 2)(5 - 2)
• 21 = 7 x 3

Rules and clarifications

• The input is guaranteed to be a positive odd integer. It may be either a composite integer or a prime.
• You're required to process any odd n in [ 1, ..., 65535 ] in less than one minute on mid-range hardware.
• Given enough time, your program/function should theoretically work for any value of n that is natively supported by your language. If it doesn't, please explain why in your answer.
• You may use any other method instead of the described one as long as it returns the correct result.
• This is code golf, so the shortest answer in bytes wins!

Test cases

To be completed

Answer 14

Dungeon of Botdom

Bots will play a variant of this game:

https://boardgamegeek.com/boardgame/150312/welcome-dungeon

(Our version will be played by one bot versus another bot, and there will only be one character, which may or may not be in the actual game, and it will be repeated a bunch.)

Essentially, there is a deck of cards, with enemies on each card. players take turns either passing, or drawing a card and either a) placing it in the initially empty dungeon or b) removing a piece of gear and discarding the enemy. enemies have different hit points, which affects the damage done to a bot traversing the dungeon. When everyone but one player has passed, they enter the dungeon. when a bot is traversing the dungeon, they will encounter the enemies placed in the dungeon in LIFO order (the card on top is taken first) (if I take out some items this may be irrelevant). enemies are instantly defeated if the player has a corresponding item, otherwise the player takes damage equal to the enemies number. if a player makes it through the dungeon, they get one point. get two points to win the match. if they fall while traversing the dungeon, they lose one chance. fail twice, and the opponent wins the match.

What this means, is that you might want to do one of two things: make the dungeon too dangerous to survive without your opponent thinking it is, and passing, or making the opponent bot believe the dungeon is too dangerous, when it is not, and running through the dungeon and succeeding.

We'll have a good ol' round robin of a 1000 rounds each or some such. the nice thing about this game is that the rounds are short, because once you finish the deck, a player automatically enters the dungeon.

Answer 15

Can my favourite team still become Football Champion? code-golf

As a fan of an at most moderately successful football^BE team, towards the end of the season I often wonder whether my favourite team still has any theoretical chance left of becoming champion. Your task in this challenge is to answer that question for me.

Input

You will recieve three inputs: the current table, the list of remaining matches, and the current position of the team we are interested in.

Input 1: The current table, a sequence of numbers were the i-th number are the points gained by team i so far. For example, the input [93, 86, 78, 76, 75] encodes the following table (only the last column is of importance):

---

Input 2: The remaining matches, a sequence of tuples where each tuple (i,j) stands for a remaining match between team i and j. In the above example, a second input of [(1,2), (4,3), (2,3), (3,2), (1,2)] would mean that the remaining matches are:

Chelsea vs Tottenham, Liverpool vs Man. City, Tottenham vs Man. City, Man. City vs Tottenham, Chelsea vs Tottenham

---

Input 3: The current position of the team we are interested in. For example, an input of 2 for the above example would mean that we'd like to know whether Tottenham can still become champion.

Output

For each remaining match of the form (i,j), there are three possible outcomes:

• Team i wins: Team i gets 3 points, team j gets 0 points
• Team j wins: Team i gets 0 points, team j gets 3 points
• Draw: Team i and j both get 1 point

You must output a truthy value if there is some outcome for all remaining games such that at the end, no other team has more points than the team specified in the 3rd input. Otherwise, output a falsy value.

Example: Consider the exemplary input from the above section:

Input 1 = [93, 86, 78, 76, 75], Input 2 = [(1,2), (4,3), (2,3), (3,2), (1,2)], Input 3 = 2

If team 2 wins all its remaining matches (i.e. (1,2), (2,3), (3,2), (1,2)), it gets 4*3 = 12 additional points; none of the other teams gets any points from these matches. Let's say the other remaining match (i.e. (4,3)) is a draw. Then the final scores would be:

 Team 1: 93, Team 2: 86 + 12 = 98, Team 3: 78 + 1 = 79, Team 4: 76 + 1 = 77, Team 5: 75

This means that we have already found some outcome for the remaining matches such that no other team has more points than team 2, so the output for this input must be truthy.

Details

• You may assume the first input to be an ordered sequence, i.e. for i < j, the i-th entry is equal to or greater than the j-th entry. The first input may be taken as a list, a string or the like.
• You may take the second input as a string, a list of tuples or the like. Alternatively, you may take it as a two-dimensional array a where a[i][j] is the number of entries of the form (i,j) in the list of remaining matches. For example, a[1][2] = 2, a[2][3] = 1, a[3][2] = 1, a[4][3] = 1 corresponds to [(1,2), (4,3), (2,3), (3,2), (1,2)].
• For the second and third input, you may assume 0-indexing instead of 1-indexing.
• You may take the three inputs in any order.

Please specify the exact input format you chose in your answer.

_{Side node: The problem underlying this challenge was shown to be NP-complete in "Football Elimination is Hard to Decide Under the 3-Point-Rule". Interestingly, if only two points are awarded for a win, the problem becomes solvable in polynomial time.}

Test Cases

All test cases are in the format Input1, Input2, Input3.

Truthy:

• [93, 86, 78, 76, 75], [(1,2), (4,3), (2,3), (3,2), (1,2)], 2
• [50], [], 1
• [10, 10, 10], [], 3
• [15, 10, 8], [(2,3), (1,3), (1,3), (3,1), (2,1)], 2

Falsy:

• [10, 9, 8], [], 2
• [10, 9, 9], [(2,3), (3,2)], 1
• [21, 12, 11], [(2,1), (1,2), (2,3), (1,3), (1,3), (3,1), (3,1)], 2

Winner

This is code-golf, so the shortest correct answer (in bytes) wins. The winner will be chosen one week after the first correct answer is posted.

Answer 16

Closely related to Words from periodic table of elements (but that one is closed due to unclear specification?).

Closely related to Find the Chemistry of a name (probably a dupe, slightly different requirements though).

Closely related to [Br]eaking Code Golf [Ba]d (allows strings to be not expressible as solely a sequence of element abbreviations).

May I get a community consensus, whether this is better specified and/or sufficiently different to not be immediately closed as a dupe?

Elementize a string

Convert an input string to a concatenation of chemical element abbreviations.

Write a program/function/procedure etc. which will take as input a string/array of characters/pointer to a string etc. and return/print/display the same string expressed as a concatenation of chemical element abbreviations.

For example, takagi can be expressed as TaKAgI (i.e. the abbreviations for Tantalum(Ta), Potassium(K), Silver(Ag), Iodine(I)).

For this challenge you must use the following element name abbreviations:

{"H", "He", "Li", "Be", "B", "C", "N", "O", "F", "Ne", "Na", "Mg",
"Al", "Si", "P", "S", "Cl", "Ar", "K", "Ca", "Sc", "Ti", "V", "Cr",
"Mn", "Fe", "Co", "Ni", "Cu", "Zn", "Ga", "Ge", "As", "Se", "Br",
"Kr", "Rb", "Sr", "Y", "Zr", "Nb", "Mo", "Tc", "Ru", "Rh", "Pd",
"Ag", "Cd", "In", "Sn", "Sb", "Te", "I", "Xe", "Cs", "Ba", "La",
"Ce", "Pr", "Nd", "Pm", "Sm", "Eu", "Gd", "Tb", "Dy", "Ho", "Er",
"Tm", "Yb", "Lu", "Hf", "Ta", "W", "Re", "Os", "Ir", "Pt", "Au",
"Hg", "Tl", "Pb", "Bi", "Po", "At", "Rn", "Fr", "Ra", "Ac", "Th",
"Pa", "U", "Np", "Pu", "Am", "Cm", "Bk", "Cf", "Es", "Fm", "Md",
"No", "Lr", "Rf", "Db", "Sg", "Bh", "Hs", "Mt", "Ds", "Rg", "Cn"}

These are the elements with numbers 1 through 112. You may optionally also use the abbreviations for elements 113 through 118:

{"Nh", "Fl", "Mc", "Lv", "Ts", "Og"}

You may not, however, use the placeholder three-letter abbreviations for not yet named elements, such as "Uuo" (Ununoctium).

If the input string cannot be expressed by the above abbreviations, you shall return one of the following:

• a falsey value (clearly distinct from element names, in other words A would not be valid, even though there is no element "A"; something like 0, null, false, newline is fine)
• an empty string
• exit without output
• exit with an error
• something similarly unambiguous signifying failure and not returning some incorrect output that could be accidentally misinterpreted as an answer (suggestions to make this specification clearer?)

Possible output, using example input takagi:

• an appropriately capitalized string: TaKAgI.
• a flat array of characters {"T", "a", "K", "A", "g", "I"} with appropriate capitalization.
• a list of strings (capitalized or not) separated by newlines or as separate members of an array, etc., e.g. ta \n k \n ag \n i.

The rule of thumb is that the division into separate elements must be clear. Please comment if additional clarification is needed!

You may assume the input to be a single word consisting only of letters.

Compression is not the intent of this challenge! Boiler-plate code that fetches the list of elements from somewhere, hard-coding the lists of abbreviations, assuming the list of abbreviations to be stored in a variable or passed as a second argument to your function is OK and should not be included in the byte count.

Sample input -> sample output
no -> No             // as in Nobelium, alternatively see next line
no -> NO             // Nitrogen-Oxygen, either one is valid
helium -> falsey output
heliam -> HeLiAm
fog -> FOg           // If using 118 elements, falsey otherwise.
ppcg -> falsey       // I'm really, really sorry

Suggestions of further test cases are appreciated.

This is code-golf, shortest code wins.

Answer 17

How many substitutions till palindromization?

code-golfstringpalindrome

Given a string, find the minimum number of character substitutions needed so that the string is a palindrome.

E.g. the string abchefa needs 2 substitutions, so it can take any of the following paths:

abchefa -> afchefa -> afehefa
                   -> afchcfa
        -> abehefa -> afehefa
                   -> abeheba
        -> abchcfa -> afchcfa
                   -> abchcba
        -> abcheba -> abeheba
                   -> abchcba

You must return a minimal number, e.g. abc can use 3 substitutions (abc -> dbc -> ddc -> ddd) but it really only needs 1 (abc -> aba) so you must return 1.

The string will only contain printable ASCII, no newlines.

Additional testcases:

Input
Output


0

A
0

!@
1

1234567890
5

 !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
47

aaabaaacaqadaaq
3

o_O WTF RLY?!
6

Rules

• You can take the string as a string or as a list of chars, but not as a list of strings
• You must return a minimal value in a generally accepted output format.

Answer 18

Write machine code that also works when left rotated one byte

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Write machine code for a CPU that runs and does something. The twist is that your code should run and do something else, without errors, if it is left rotated one byte.

Suggestions? Ideas? Thoughts? Let me know.

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code-challenge

Answer 19

Reverse divmod

code-golf number

Introduction

The divmod function is one that is included in many standard libraries and is defined as follows:

Or, in other words, divmod(a,b) returns a list containing the integer quotient of a/b (i.e. floor(a/b)) and mod(a,b) (i.e. the remainder in the division of a/b).

Your challenge is not to implement the divmodfunction, but rather reverse it.

Input

You will take two integers x and y as input, in any reasonable input format (two integers, list, etc.). Both x and y are guaranteed to be in the range -2^31 to 2^31-1, inclusive.

Output

The output of your code shall be two integers, in any reasonable output format (two integers, list, etc.). Note that you must output the two integers in such a way that a human is able to distinguish one from another. These two integers should be an a and b such that divmod(a,b)==(x,y) (i.e. floor(a/b)==x && mod(a,b)==y). Please specify in your answer how these two integers are outputted if it is not immediately clear (for example, if you output b before a).

Remember that this is code-golf, so shortest solution in bytes wins!

Answer 20

Help me golf my numbers! (Part 2) code-challenge test-battery

Thanks for all your help in Part 1! I recently just found out that my language also supports expressions, and we can use those to make our numbers even shorter!

Challenge

Write a full program that takes in a list of integers less than 2^53-1. For each integer, rewrite it in the shortest way possible using expressions, and output the result.

Allowed operators

The operators below are given in order of precedence from highest to lowest, with groups separated by empty lines. (These precedence levels are the same as Python.) All binary operators are left-associative, except exponentiation, which is right-associative. Note that some operators are two bytes in length.

**: Exponentiation

* : Multiplication
/ : Integer Division
% : Modulus

+ : Addition
- : Subtraction
~ : Bitwise NOT

<<: Left shift
>>: Right shift

& : Bitwise AND

^ : Bitwise XOR

| : Bitwise OR

You may use decimal, hexadecimal, or scientific notation to represent integers in your output (the answers to Part 1 will help you choose the shortest representation for each integer). You may also use parentheses to group subexpressions.

Scoring

I will post a list of 1000 integers to be used as the test battery. A program's score will be the size of the output for the provided test, where the lowest score wins. A solutions is invalid if any of the expressions do not evaluate to the given integer. There will also be an execution time limit of 20 minutes for all 1000 inputs (roughly 1 second per input) in order to discourage brute-force solutions.

Numbers for the test battery will be chosen according to the following algorithm:

def choose():
    msb = randint(0, 52)
    return randint(0, 1 << msb)

with duplicates filtered out.

Sandbox

• Is there anything here that can be clarified?
• Anything else that can make this challenge more fun?

Answer 21

Insert a simulated Ken Thompson virus into a program code-golf code-generation

A Ken Thompson virus is a virus that infects your compiler and other programs. Since it infects all your tools, you can not detect it without using tools from before the virus was introduced.

Your will create a prototype for inserting the Ken Thompson virus into code. The goal of this virus will be to allow you to (fake) destroy any computer running a program infected with it.

Inserting a Ken Thompson virus is defined as follows. Start with an input program P. Your program will output a modified program Q that works as follows:

• If the input to Q is aNouIQ5xKvUfdZVzo0Xs, it will output BOOM (in a real Ken Thompson virus, this would actually do something bad, but since it this is a fake virus, outputing BOOM is done instead).
• For any other input to Q, run program P with that input
  • If the output of P is valid source code in the language you are using, insert the Ken Thompson virus into it and then Q will output the resulting infected program.
  • Otherwise, the output of Q is just the output of P.

You will write a program that takes P's code as input and produces Q's code as output.

You can use either a currently (at the time of this post) existing programming language, or a subset of one, for this challenge. (The idea is that language you are using would be the target language of some self-compiling compiler, but this is not required.) Since you want to be as subtle as possible, the shortest code (in bytes) wins!

Answer 22

Find the Harmonic Mean

code-golf

The harmonic mean of a sequence of numbers is the reciprocal of the arithmetic mean of the reciprocal of each number. For example, the harmonic mean of [1, 2, 3] is 1/((1/1+1/2+1/3)/3) = 3/(1/1+1/2+1/3).

Input

A list/array/tuple/string with some delimeter/etc. of positive integers which fit within the standard integer/float type of your language of choice.

Output

The harmonic mean of those integers, accurate to at least 6 (?) decimal places.

Test Cases

input => output

1 4 4 => 2.0

1 2 3 => 1.63636

527 => 527.0

52 33 400 => 52.6548

7 20 333 45 1 => 4.10481

Answer 23

The problem

As I sometimes build bots, I often came across real time image reading. The goal in this problem is to be able to identify a character given pixel representation with the minimal amount of tests. For that, you will have to generate a tree that can identify any char.

Input

• A list of frequency
• A png file containing each char in a 1 wide red box. Its exact color is #ed1c24 and it is not present in any of the chars.

Output

A series of specific test that can identify any char. A test is defined by the pixel coordinates, the exact colour to check, the list of chars to have this pixel and the list of chars that donot.

Example

Let's have a look at only four chars (number 1-4) of equal frequency.

Here we could say that we check for the for pixel in 0,0 (upper left corner). If it is white, it means it's a 1, otherwise we check for the pixel 1,0 (to the right of the upper left corner). If this one is white, it's a 4, otherwise we check for the pixel in 2,2 (the blanck beetween the 3 and the box). If it is white, it's a 3, otherwise it's a 2.

That way we can identify any number in 3 tests at most. If we calculate our score with this layout, it would be 0.25x1 + 0.25x3 + 0.25x3 + 0.25x2 = 2.25 so on average our tree needs 2.25 pixel reading to identify a number.

The solution that lead to that is written like this:

[0,0], [255,255,255], [1], [2,3,4]
[1,0], [255,255,255], [4], [2,3]
[2,2], [255,255,255], [3], [2]

However the best solution for this example has a score of 2. One of the trees that lead to that is

[0,1], [255,255,255], [1,4], [2,3]
[0,0], [255,255,255], [1], [4]
[2,2], [255,255,255], [3], [2]

Rules

• Count each time you read a pixel.
• Use the number frequency to average your score
• Your score is the sum of the char frequency times the number of pixels read to identify this number.

Answer 24

Sources and Strings

The challenge: Output a string with the same length as the source code.

The requirements:

• Standard loopholes apply, etc., etc.
• Input may not be taken
• The output must be deterministic (for scoring purposes)
• Output must be a string
• Functions and full programs are allowed, no snippets though

The scoring: This is code-golf, so the shortest code in bytes wins. However, for each individual character in the source that has a match in the outputted string, your byte score is increased by 2 bytes.

Examples of scoring (of course, most of these aren't working programs):

Program            Output            Score
nn                 ng                2+(1*2)=4
print('h'*14);     hhhhhhhhhhhhhh    14+(1*2)=16
print('prnt'*4);   prntprntprntprnt  16+(8*2)=32
q                  q                 1+(1*2)=3
qwertyuiop         mmmmmmmmmm        10+(0*2)=10
System.out.println("lol");           Invalid=Infinity points

Answer 25

Prime Factors Zip

Take an integer strictly greater than 2, for example 66. Its prime factors are [2,3,11], when ordered from smallest to biggest. If we zip the digits of those factors, we get [231,1]. Multiplying them yields the integer 231.

If we apply this process back on 231, we get 371. If we apply this multiple times, we get the following sequence:

66
231
371
225
3355
5676
290082
770229
174999300
121860997014
6330393355581
40168037420160
6869559509647641812624
0

At this point, we stop because 0 cannot be factored. We say that 0 is the prime factors zip of 66.

If we start with 19, we get the following sequence:

19
9
33
31
3
3
…

Here, we can see that once we reach 3, we will always get 3. Therefore, 3 is the prime factors zip of 19.

If we start with 22, we get the following sequence:

22
21
37
21
37
…

Here, we can see that once we reach 21, we will always get the loop [21,37]. Therefore, [21,37] is the prime factors zip of 22.

Note that it is possible for an integer to be its own prime factors zip (e.g. 5) or that it is contained in its prime factors zip (e.g. 23 which has prime factors zip [23,6]).

Task

Given an integer strictly greater than 1, output its prime factors zip.

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

Test Cases

Input        Prime factors zip
7            7
46           0
48           [22103,72463]
100          0
113          3
1337         [337,63]    

Sandbox

I have no idea (nor have I checked extensively) if it is possible than this procedure never loops for some integers.

Answer 26

Color the Grayscale

code-golf image-processing

Given an image containing only grayscale colors (for RGB, R==G==B), and a RGB value (that is not grayscale), color the image with your given color.

//Is there a formula that does this? If so this can definitely have objective input and output.

Should this be popularity-contest like a lot of the other image-processing challenges?

Answer 27

This question is up for adoption! If you would like to finish and post it, please include a little mention for @gryphon :)

Battle of the Bots

Your Task

Program a bot to compete in a battle with other bots. Each robot has fifteen flags situated around their exterior. Your goal is to have at least one flag left on your robot for as long as possible. Each turn you will move diagonally (or not at all) on a square grid with a width/length equal to the number of bots competing squared (attempting to move off the edge of the grid will result in either you moving adjacent to your previous position, or no movement at all if attempting to move from a corner), and use two or less of the four weapons/shields that are situated facing along the horizontal and vertical rows of the grid. You will choose which weapon you would prefer to have in each of your four slots at the beginning of the game. After 2,500 turns, each bot with flags remaining will receive a 500 point bonus, and the game will end. If all flags have been destroyed before this time, the game will end then. The winner will be the person with the most points at the end of 1,000 matches.

Your Code

Each bot will begin in a randomly chosen location on the playing field (bots may be on top of each other). Your code will take the form of two python 2.7 functions, one named (name of your submission) start, which will take no input and return 4 values, one for each weapon/shield slot. The first value will be the top of the bot, and they will continue in clockwise order. The integer values to be returned and weapons/shields they represent are shown below:

1: Firestarter, a weapon that will start a fire adjacent to the bot. Fires start at class 1 and increment upward every turn. If, at the start of a bot's turn they are on top of a fire they lose flags equal to the level of the fire. If a fire is at level 3, it spreads fires of level 1 to all directly (not diagonally) adjacent squares that are not already on fire. When a fire reaches level 8, rather than becoming a level 8 fire, it dies, turning back to an "O" on the map, having used up all available burning material. It may then be lit on fire again in the future.

2: Laser, a weapon that destroys one flag on any bot in a straight line from its firing point outwards from the bot.

3: Buzzsaw, a weapon that destroys five flags on any bot adjacent to the bot using it on the side it is used on.

4: Shield, a defensive mechanism that protects flags from lasers and buzzsaws, and is unaffected by our next weapon.

5: Acid Sprayer, a weapon that destroys the weapon facing it on any bot within three spaces of the bot using it in a straight line (not an arc) from its mounting point

Your second function will receive, first the turn number, second a map of the battlefield in a string, with "R" representing robots (including itself), "O" representing empty space, and the level a fire is at representing any fires. The end of a row will be shown with a semicolon ";". For example, if the battlefield looks like this:

OORO131OO
OOOOO1OOO
ROOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOROOO
OOOOOOOOO

Each bot will receive this:

OORO131OO;OOOOO1OOO;ROOOOOOOO;OOOOOOOOO;OOOOOOOOO;OOOOOOOOO;OOOOOOOOO;OOOOOROOO;OOOOOOOOO

Next, the bot will receive its X coordinate, and then its Y coordinate, 0 indexed and with the top left corner being 0,0. Finally, the bot will receive how many flags it has remaining.

If multiple bots are in the same square, only a single "R" will be shown. If a bot is standing on the same square as a fire, only the fire will be shown. A bot can tell if it is standing on a fire if its own X and Y coordinates show an integer rather than a "R".

Sample Bots

Will show sample bots here when they are completed

Controller

Will show controller here when it is completed

Additional Rules

• No copying other bots, or copying with only minor changes.

• No messing around with the judging process, other bots, or writing programs to acquire information that does not come from the inputs given to them, randomizers, or other legitimate sources of information.

• No writing bots specifically designed to prop up other bots.

• Maximum of three submissions per user.

Meta:

Is the explanation clear enough?

Are there any loopholes for programs to exploit?

Any tags other than king-of-the-hill?

Answer 28

Print all video urls of YouTube channel codegolf

Inspired by Count the videos in a Youtube Playlist, the input will be the "VIDEOS" view from a channel like this one:

https://www.youtube.com/channel/UCzwJRQXMXkaB9KlqUdFD74Q/videos

The output will be a complete, newline-delimited list of all video urls the respective channel has to offer. It would look something like

https://www.youtube.com/watch?v=JxNfccUIQCU
https://www.youtube.com/watch?v=lOr0XIHFhlk
https://www.youtube.com/watch?v=o3tZElWLrbc

This is codegolf, so shortest answer wins.

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Comments:

• I am unsure whether the permitted use of Google's YouTube API might be a good idea. It requires an API_KEY and can only retrieve 50 results per request.

Thanks for the feedback.

Answer 29

Patch Tuesdays Calendar

Context

Patch Tuesday happens every second Tuesday of the month, Microsoft and other companies release their monthly security patch on that Tuesday.

Challenge

The challenge is to write a program that writes 24 consecutive Patch Tuesdays dates separated by newline to the console. The Tuesdays must be the ones of the current year and the next year (not a parameter). Date format must be mm/dd/yyyy.

Winning

Code with the fewest bytes wins, there are no bonuses.

Meta

Is there a good write up with conventions for golf questions?

Answer 30

Challenge

My challenge, is for you to generate a Menger Sponge based on the level/iteration given. You need to draw it in 3d, see the Specifications below!

3D Specifications

• You can use existing 3D libraries

Examples

Inputs: 0, 1, 2, 3

Outputs:

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Background Information

What is a Menger Sponge

In mathematics, the Menger sponge (also known as the Menger universal curve) is a fractal curve. It is a three-dimensional generalization of the Cantor set and Sierpinski carpet

Properties

See https://en.wikipedia.org/wiki/Menger_sponge#Properties (too long to copy and paste)

How do I construct the sponge?

1. Begin with a cube (first image).

2. Divide every face of the cube into 9 squares, like a Rubik's Cube. This will sub-divide the cube into 27 smaller cubes.

3. Remove the smaller cube in the middle of each face, and remove the smaller cube in the very center of the larger cube, leaving 20 smaller cubes (second image). This is a level-1 Menger sponge (resembling a Void Cube).

4. Repeat steps 2 and 3 for each of the remaining smaller cubes, and continue to iterate ad infinitum.

The second iteration gives a level-2 sponge (third image), the third iteration gives a level-3 sponge (fourth image), and so on. The Menger sponge itself is the limit of this process after an infinite number of iterations.

Credit

Background info taken from this wikipedia page on Menger Sponges.

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Good Luck!

Remember this is code-golf the shortest program wins!

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HELP

I need help with specifications for the 3d output:

Since 3D is now required (invalidating existing answers), I think the question is now unclear. There is a lot you need to specify for 3D including but not limited to viewing angle, projection, lighting, shading.