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

The sandbox works best if you sort posts by active.

To add an inline tag to a proposal, use shortcut link syntax with a prefix: [tag:king-of-the-hill]. To search for posts with a certain tag, include the name in quotes: "king-of-the-hill".

Answer 1

Remove odd indices and double the even indices

Answer 2

Answer 3

Score a Scrabble Play

Answer 4

Find the index of the matching parentheses for each character

Answer 5

Find my Māori pronouns

Answer 6

Print 2^n graph in ASCII

Your challenge is to output this infinite graph:

o
o
oo
oo
oo
oo
ooo
ooo
ooo
ooo
ooo
ooo
ooo
ooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
oooo
ooooo
ooooo
ooooo
ooooo
ooooo
ooooo
...

with the xth line having floor(log_2(x)) os (or other characters). Tag: code-golf, ascii-art, kolmogorov-complexity.

Answer 7

Is it a tower permutation?

Answer 8

Gambling with an Alien

code-golf decision-problem

Find the challenge here!

Answer 9

Crate art stacking

Answer 10

Repeat List Until Longer

Answer 11

The Missing Match

Answer 12

What does the text talk about?

code-challenge machine-learning string note that the machine-learning tag will be new

META: this is far from being done. I also understand that this challenge depends heavily on manual opinion about the "type" of a piece of text. Hence, if you take issue with that, I would appreciate your giving a comment that suggests ways to fix that issue, rather than an unjustified downvote related to that issue.

Additionally, this might be a duplicate. I would appreciate your pointing this out before I compile the list of texts, if possible. However, if you identify a duplicate after I start compiling the list of texts, that is also fine.

Some parts use the future tense to talk about what I will do. Obviously I will have done them by the time I post the challenge.

The sections in italic could be taken as being ambiguous.

The links to the training, validation and test sets are not available yet. And of course, I don't yet have labels on my side.

---

This is a project that I once attempted to do, having learned machine learning. I run a forum app, and I was thinking of incorporating my new machine learning knowledge into that app by creating a model that could detect topics related to a given topic. After having worked on it for a few days, I hadn't made much progress, so I abandoned it. I hereby challenge you to make a similar model, ideally with machine learning, but that is not required. Your model will classify the topic of a piece of text. Such a model could then be used to find text related to a given piece of text by finding texts with a similar topic. You can choose to write your model without machine learning.

This is thus essentially a machine learning challenge. (or ideally, it will be. You may choose to write your solution without machine learning, but I am mainly looking forward to seeing machine learning solutions.) I will provide a large set of "articles", divided into a training set, a validation set, and a test set, with a 60-30-10 split. I expect there to be about 500 articles in all.

The articles in the training and validation sets are labeled with their topics: for instance, history, geography, mathematics, programming, etc. The test set, importantly, does not have public-facing labels, but I have labels on my side.

The training set is available here.

The validation set is available here.

The test set is available here.

Challenge

Write a classifier that attempts to classify the topic of a piece of text. The possible topics are:

(coming soon)

You can choose any of (coming soon) distinct values to represent the topic.

It should be able to produce an output that is one, and only one, of the chosen distinct values given any input string.

You have access to the train set to teach your classifier to recognize the topics (if you are using machine learning). The validation set can be used to compare different approaches.

Your submission will be scored based on how well it does on the test set. I will write the test set articles in such a way that they are not ambiguous (500 years ago, a mathematician discovered a method to calculate integrals is ambiguous as the sentence could be about mathematics or history, but Learn about the way people lived 1000 years ago is only about history). Your score is the number of articles it can correctly classify out of the test set. The higher the number of articles your submission can correctly classify, the better the score is. Thus the winner of this challenge is the submission that classifies the most articles correctly.

Importantly, this is not code-golf. I expect this to be a challenge that demands significant time and effort to produce a solution that scores highly, so you may post a link to a GitHub repository hosting the solution if required.

You are encouraged to either provide a way to easily run your solution, or provide the list of outputs that your code produces when given the test set articles. Even better, you could post a Jupyter notebook (if you are answering with a supported language) containing your solution, complete with test set outputs.

Important: please do not post a solution that is optimized only for the test set. It should work reasonably well in general.

Just so that you can get an idea of the topics:

Article: The dinosaurs went extinct 66 million years ago due to an asteroid impact.
Topic: history

Article: Time complexity is a measure of the complexity of an algorithm. For instance, the operation of adding two integers is usually taken to have a complexity of O(1). The operation of summing a list given as input has a complexity of O(n) where n is the size of the input.
Topic: programming

Article: Partial derivatives are derivatives taken with respect to one variable.
Topic: mathematics

Article: Planes are for going on holiday, especially island getaways.
Topic: holiday

Article: Carrot Cake Potato Mushroom
Topic: food

Answer 13

Matrix Meets ASCII Art

Answer 14

Haplololololololology!

Answer 15

Straighten my corners... diagonally

Answer 16

Make the list Fibonacci-like

Answer 17

The Magic Money Machine

This KOTH is based on a game of Tom Scott's series Money, so make sure to check out his video

---

Challenge

There are three rounds per game. Each bot will get 100$.
They'll have to decide how much money they'll keep for themselves, and how much they're going to put in the Magic Money Machine.
The money in the Machine will get a 20% boost in the first round, a 50% boost in the second round, and a 100% boost in the third round.
Each bot will equally get the money left in the Machine.

Example:

• Bot A decides to put 60$ in the Money Machine and keep 40$ for themselves
• Bot B decides to put 30$ in the Money Machine and keep 70$ for themselves
• In total there are 90$ in the Money Machine, so with a boost of eg. 20% that's 108$, so each bot will get an additional 54$
• Bot A has 94$ in the end
• Bot B has 124$ in the end

You have to try to get as much money as possible.

Rules:

• Standard Loopholes apply
• No interaction with the controller other than by returning values.
• No interaction with other bots

API Template

def plan(round_num, others_money):
    # Tell the other bots how much money you're going to put in the Machine
    # You are allowed to lie
    return money_insert_pub

def main(round_num, others_money, others_plan):
    # Do stuff here
    return money_insert

• round_num: an integer ranging from 1 to 3, it depicts the current round
• others_money: a list of 0, 1, or 2 tuples. Each tuple will contain the money_kept var of the other bots of the last rounds (yours incl.).
• money_insert_pub: the money_insert value you're telling others
• money_insert: an integer between 0 to 100, the amount of money you put in the Magic Money Machine
• others_plan: the money_insert_pub value of the other bots (yours incl.)

Controller code is on Github

Example bots

Beep Boopy Random

import random
def plan(round_num, others_money):
    global money_insert
    money_insert = random.randint(0, 100)
    return money_insert

def main(round_num, others_money, others_plans):
    return money_insert

Random copycat

import random
def plan(round_num, others_money):
    return 100

def main(round_num, others_money, others_plan):
    if round_num == 1:
        money_insert = random.randint(0, 100)
    else:
        money_insert = (
            random.choice(others_money[-1]) if others_money else random.randint(0, 100)
        )
    return money_insert

Meta

• This is my first (well sort of) KOTH, is there anything I've missed?

Answer 18

Give f and g that sometimes commute

Answer 19

Iteratively delete a list

Answer 20

Universal Unicode Clock

Answer 21

Extend a matrix in all directions

Answer 22

ro1000an nu1000era50 en100o501ng

Answer 23

Not-Roman-Numeral Addition

Answer 24

Word stays a word after taking away a letter

Posted here

Answer 25

All Possible Ties in Tic-Tac-Toe

Answer 26

Next digit of rational number codegolf string

Answer 27

Count the cells

Answer 28

Rearrange to a palindrome

Given a string, shuffle it so that it becomes a palindrome.

For example, adadbcc can be arranged into dacbcad, or dcabacd, acdbdca and more. Any of these (or all) is acceptable, and duplicates are allowed if outputting all. Something like abc cannot be shuffled into a palindrome, and you can assume it won't be inputted.

(if it helps) input will only contain lowercase letters.

Testcases

These show one possible solution.

nanas -> nasan
coconutnut -> conuttunoc
apotato -> atopota
manplancanalpanamaaaa -> amanaplanacanalpanama
canadadance -> canadedanac

Answer 29

Halve a string

Posted

Answer 30

Every \$ n \$th repeat code-golf array

Given a list of positive integers, and another integer \$ n \$, output every \$ n \$th instance of each distinct item in the list, starting with the first, in the order they appear in the original list.

For example, with \$ n = 2 \$, we will output the first instance of each item, but not the second, but we will output the third, and so on.

If \$ n = 2 \$ and the list is 4 1 3 2 3 1 6 3 4 1 1, then:

• 1 occurs four times, so only the first and third will be kept
• 4 occurs twice, and only the first will be kept
• 3 occurs three times; the first and third will be kept
• 2 and 6 only occur once each, so their first and only occurrences will be kept

Therefore, the output is 4 1 3 2 6 3 1.

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

Test cases

todo

Meta

• Related (\$ n = 2 \$, and more open ended)
• Is this a duplicate?
• Is this clear enough?