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

Plot an NACA Airfoil

popularity-contestgraphical-output

NACA airfoils are described using a series of digits that represent the miscellaneous properties of the airfoil profile.

The purpose of this challenge is to receive an airfoil number as input, and plot the profile of the airfoil.

Background information:

4-digit NACA airfoils are generally described by their string NACA ABCC, where A,B are single digit integers, and CC is a 2-digit integer.

• A is the maximum camber as a percentage of the chord length. Eg. A=2 means that the camber is 2% of the chord length.
• B is the location (divided by 10) of maximum camber as a percentage of the chord length. Eg. B=4 means that point of maximum camber is 40% down the length of the chord.
• CC is the profile thickness as a percentage of the chord width. Eg. CC=12 means that the width of the airfoil is 12% of the maximum chord length.

Using the example given above, NACA2412, a suitable profile plot would look something like this:

Note that in the image above, the Red line is the camber line and the purple is representative of the symmetrical airfoil NACA 0012.

Any airfoils with a representative number of NACA 00XX are symmetrical in nature because they possess zero camber.

Possible scoring criteria are code-golf and popularity-contest

Any feedback is welcome. I also plan on having more challenges for the 5-digit and 6-digit profiles. Eventually, I will add equations to this post too.

Another way this challenge could be run would be to have the programmer return a series of points around the profile. This could be judged both for accuracy and quantity of points returned. If this approach is used, this would probably be a code-golf challenge.

Answer 2

Optimize the JSON (WIP)

Consider function f which takes two objects data and default, and merge anything from default into data if data contains no such element. Take the two objects(if the one in your language can handle the required elements) or JSON as input, output a shortest JSON that, when given as data, output the same object as the original data do, as long as default doesn't change.

Answer 3

Draw these shapes

Given: a width, a height, and a set of sets of points. Output: An image where each set of points is connected and colored in (like a shape). Each shape must be a different color from all of the other shapes, but the difference doesn't matter. The shapes must be in order; whether you start at the end or the beginning of the set doesn't matter, though.

Examples

//the code here has nothing to do with the actual challenge and just shows examples

document.getElementById("one").getContext("2d").fillRect(0, 0, 300, 300)
const ctx = document.getElementById("two").getContext("2d")
ctx.fillStyle = "black"
ctx.beginPath();ctx.moveTo(0,0);ctx.lineTo(0,300);ctx.lineTo(300,0);ctx.closePath();ctx.fill()
ctx.fillStyle = "lime"
ctx.beginPath();ctx.moveTo(200,0);ctx.lineTo(600,0);ctx.lineTo(300,300);ctx.closePath();ctx.fill()

canvas {border: 1px dotted black}

<pre>Width: 500, Height: 500, Set: [[[0, 0], [0, 300], [300, 300], [300, 0]]]</pre>
<canvas id="one" width="500" height="500"></canvas>

<pre>Width: 600, Height: 300, Set:
[
  [[0,0], [0,300], [300,0]],
  [[200,0], [600,0], [300,300]]
]</pre>
<canvas id="two" width="600" height="300"></canvas>

Scoring is code-golf.

Answer 4

Patch one line

First question I've written, feedback is highly appreciated. If you can think of a clever title, I'll take that too.

---

Challenge

In an effort to prove to your employer that Git commit count is a worthless metric, you've decided to break up all your changes from now on line by line.

Golf a program which can edit a patch file to remove all changed lines except for one.

Patch file format

The patch file will be given by Git in the unified diff format, although git will append multiple file changes together:

diff --git a/afile b/afile
index bf70e9e..d2df230 100644
--- a/afile
+++ b/afile
@@ -1,8 +1,9 @@
-Lorem ipsum dolor sit amet,
+Lorem IPSUM dolor sit amet,
+++ (good luck parsing this line)
 consectetur adipiscing elit.
    Duis est elit, imperdiet ac dolor quis,
    volutpat commodo nunc.
diff --git a/bfile b/bfile
index c484b2b..db4afe5 100644
--- a/bfile
+++ b/bfile
@@ -1,11 +1,7 @@
-#
-# /etc/bash.bashrc
-#
-
 # If not running interactively, don't do anything
 [[ $- != *i* ]] && return
 
 [[ $DISPLAY ]] && shopt -s checkwinsize

Here are two accepted outputs for the above patch file:

diff --git a/afile b/afile
index bf70e9e..d2df230 100644
--- a/afile
+++ b/afile
@@ -1,8 +1,9 @@
 Lorem ipsum dolor sit amet,
+++ (good luck parsing this line)
 consectetur adipiscing elit.
    Duis est elit, imperdiet ac dolor quis,
    volutpat commodo nunc.

diff --git a/afile b/afile
index bf70e9e..d2df230 100644
--- a/afile
+++ b/afile
@@ -1,8 +1,9 @@
-Lorem ipsum dolor sit amet,
 consectetur adipiscing elit.
    Duis est elit, imperdiet ac dolor quis,
    volutpat commodo nunc.
diff --git a/bfile b/bfile
index c484b2b..db4afe5 100644
--- a/bfile
+++ b/bfile
@@ -1,11 +1,7 @@
 #
 # /etc/bash.bashrc
 #
 
 # If not running interactively, don't do anything
 [[ $- != *i* ]] && return
 
 [[ $DISPLAY ]] && shopt -s checkwinsize

Assumptions

Any other corner cases I'm missing?

You do not need to handle the following cases:

• A file is deleted, renamed, or added
• A file has changed its mode

You do need to handle the following cases:

• An added line starts with ++
• A removed line starts with --
• There are changes in multiple files (although you can remove one of the diffs and git will still patch okay)

Input/Output

Is this much explanation necessary?

I added the stdin/stdout method since I imagine it's more conducive to golfing in some langs... Should I do any kind of bonus/penalty?

Your program may either take the name of the patch file as its first parameter and do an in-place edit (this will let GIT_EDITOR=/path/to/your/program git add -e apply the patch), or read from stdin and write to stdout such that the following will correctly apply the patch:

$ cat > oneline.sh << EOF
#!/bin/sh
mv "$1" "$1.old"
/path/to/your/program < "$1.old" > "$1"
EOF
$ chmod +x oneline.sh; GIT_EDITOR=./oneline.sh git add -e

Refer to the EDITING PATCHES section of man git-add for some helpful info on editing the patch file.

code-golf parsing

Answer 5

A Gödel numbering

Task

In order to solve this challenge, you need to enumerate all possible programs in a turing-complete language given by you.

Rules

• Either, you need to provide a function from a string-like type into a big-nat-like type, or you need to provide a program reading the program from STDIN and printing its Gödel number into STDOUT.

• Your function needs to be bijective, such that every different (as given by its behaviour) function gets mapped to a different natural number.

  • Example: If your turing-complete language is Brainfuck where I/O is the tape before/after the program ran, +- and ++-- may be mapped to the same number, since they both are no-ops.
• Your program must terminate for every possible input.
• Give a specification of your used language in the post or link it.
• This is a code golf (measuring in bytes).

Answer 6

Mutual quine without sharing characters

Write a chain of at least 2 programs in different languages, that each program except the last one outputs the next, and the last program outputs the first. You may not reuse a character used in one program in any other programs.

Each language you use must have an entry in Fewest (distinct) characters for Turing Completeness.

Your score is the sum of the square of the best score in that challenge for each language you use. Highest score wins. Other users could challenge your score by posting better answers in that challenge.

---

Problems:

• Bytes / characters.
• How to define a proper quine for mutual quines? Without the restrictions specific to this challenge, someone will probably just print a string in most of the languages, and do all the encoding job in one most powerful language. But it might be not that relevant in this case, as that would most likely result in reusing characters.
• Scoring: sum(a_n^k - c), currently k=2 and c=0.
• Is this cops-and-robbers?

Answer 7

Is the Art Gallery Fully Guarded? (WIP)

code-golf decision-problem grid geometry

---

The Art Gallery Problem is a well-studied visibility problem concerning the minimum number of guards that must be placed within a polygon. This challenge will explore a simplified grid-based decision-problem variant to make input and visibility checking simpler.

You will receive a grid of walls and floors as input, representing the layout of the art gallery, and a number of guards (either as a list of locations or another value in the grid input.) You must determine whether all floor tiles are visible by at least one guard and return a truthy value if so and a falsy value otherwise.

Visibility

A floor tile is considered visible to a guard if the line connecting the center of the floor tile to the center of the tile containing the guard does not pass through any wall tiles. If this line passes through the corner of a wall tile, visibility is not obstructed. (Sandbox: this can be an issue for floating point precision. Maybe a more discrete method should be used? Perhaps Bresenham's line algorithm?) The tile a guard occupies is also visible to that guard.

Examples

Key: . Floor, # Wall, G Guard

# . # G . .
. . # . . #
. . # # . .
# G . . . #
# # # . . #
. . . G # #

==> YES


. # . # # . . .
. # . . . . . #
. . . . . G . .
. . . . . . . .
. # . . . . . #
. # . # # . . .

==> NO

More TBD after visibility is hammered down

Rules, Notes, Assumptions

• Standard challenge rules, IO methods, and loopholes apply
• Guards may be taken in either as a list of coordinates or embedded within the grid.
• You may assume that guards will always be standing on a floor tile
• You may assume that grids will always be perfect rectangles, not jagged arrays
• You may assume that grids will never be larger than \$100 \times 100\$

Happy Golfing!

Answer 8

Calculator using only addition

Your task is to create a program or function that emulates a four-function calculator, capable of performing addition, subtraction, multiplication, and integer division. However, the catch is that your code must not use any mathematical operations other than addition. In other words, you must use only addition to implement the three other basic arithmetic operations.

Input

Your program should take two numbers and an operation as parameters. Input can come in any form, whether it's through function parameters, standard input, etc. The operation can be represented however you want. You could use +, -, *, ÷, or "add", "subtract", "multiply", "divide", or whatever else is convenient. For division, you can assume that there will be no division by 0, and that the numbers will evenly divide.

Output

Your program should output one number to STDOUT, the result of the calculation.

Restriction

As mentioned earlier, you may not use any mathematical operation in your code other than the addition operator.

Rules

• No mathematical operators other than addition, as specified above.
• Bitwise operations are not allowed, but logical and comparison operators are.
• Data type conversion is allowed.
• Negation using a built in is allowed (e.g. -x or negate(x) are both fine).
• Standard loopholes are forbidden.
• It's code-golf, so shortest answer in bytes wins!

code-golf restricted-source math

Sandbox

• Wouldn't surprise me if this is a duplicate, but I couldn't find it. If it is, just put a link to the original in the comments please.
• The input section seems like it could use some work, but I don't know what to change about it.
• Other than that, let me know if there's anything that could be improved.

Answer 9

Word Calculator code-golf

This special calculator uses words instead of numbers, with these rules:

• Addition joins two or more strings together in the same order they were inputted.

Repeated letters (example: aa, bb, etc) in the output become a single letter. If there is more than one repetition, then this is performed only on the first such instance detected, when going in a left-to-right direction.

(eg: tt becomes t, tttt becomes tt, etc)

• cat+dog+tiger = catdogtiger

• dog+cat+tiger = dogcatiger

• dog+cat+tiger+tuna = dogcatigertuna

• dog+cat+ttiger+tuna = dogcattigertuna

• dog+cat+tttiger+tuna = dogcattigertuna

  (last example was originally = dogcattttigertuna, tttt is present but only the first repetition is removed, leading to the answer as shown)

---

• Subtraction follows the same rules as the addition, but with a twist. Addition proceeds as usual, but when a subtraction is encountered, this subtracts as many characters as that string from whatever the output would have been before the subtraction.

You will not be expected to handle negative values.

• cat+dog-tiger = c

• cat+tiger-dog = cati

• cat+dog+ttiger-tuna = catdogt

• cat+dog+tttiger-tuna = catdogtt

• cat+dog+ttiger-tuna-salmon = c

• cat-dog = 0

---

---

The shortest code in bytes that performs the above addition and subtraction functions as described, is the winner.

Standard loopholes are not allowed.

Answer 10

Compute the order of a Rubik's Cube cycle without trivially counting them

See: Compute the order of a Rubik's Cube cycle without trivially counting them

I asked this question here the other day and it was closed as being a duplicate of another question which I had already linked in the original question followed by an explanation of a constraint that made the my challenge different. A discussion ensued in the comment section debating what made my question a duplicate of the other, mostly revolving around whether this constraint was observable or not.

I understand that the challenge at face value is an example of Do X without Y but I think it's still a quality challenge because:

1. The constraint does not simply exist to require people to come up with loopholes or clever workaround to preform avoid a particular commonly used feature of programming languages. It's not the same problem with an unrelated constraint to "make it interesting".

2. There really is no ambiguity in terms of whether or not the constraint is being followed for a particular answer. "Without Y" is not hard to define regardless of the language being used.

3. It changes entire approach needed for the algorithm itself, not just specifics of the implementation. The trivial solution to the question will automatically be preferred by golfers, so the answers of the "duplicate" were not very interesting to me because they mostly worked in the exact same way. By prohibiting this trivial approach, there is still a very wide range of different degrees of efficiency that are possible to achieve through different implementations, and some of these are likely better suited for some languages than others, so I feel the answers will actually show significant diversity in their implementations, which in my opinion is a hallmark of a high quality challenge.

I really think this constraint introduces a meaningfully different and interesting challenge when compared to the other question and I want to see the creative solutions that golfers will come up with to solve it. But as I originally wrote it, and even with the addition of edits I made to make it more clear, it was apparently not sufficient to reopen the question.

Can anyone think of a way to write this question or define the constraint in a way that would make it more clearly not a duplicate, or eliminate the problems brought up in the comments without restricting the implementation further?

Do you think I'm only facing this scrutiny because I'm a newer member who hasn't posted much? Would someone with more reputation that me be willing to post it on my behalf?

Answer 11

Product and Sum free set

code-golfmathsequence

Given some non-negative integer \$n\$ find a sum- and product-free subset \$S \subset \mathbb N = \{1,2,3,\ldots \}\$ of size \$|S|=n\$

EDIT: with the least possible maximum \$\max_{s\in S} s\$.

Details

• A set \$S\$ is called sum-free if for all \$a,b\in S\$ their sum \$a+b \not \in S\$.
• A set \$S\$ is called product-free if for all \$a,b\in S\$ their product \$a\cdot b \not \in S\$.

related

Examples

Note that the sets for each \$n\$ might not necessarily be unique.

  n  S
  1  {2}
  2  {2,3}
  3  {3,4,5}
  5  {4,5,6,7}

EDIT: Ok, no this doesn't work either.

Answer 12

Use input letters to create as many words as possible

---

I have the scrabble letters as magnets on my fridge and I was thinking: how many actual words could I make using only these letters. Obviously it would be hard to work out myself, so I challenge you to create a program which will take a string of characters as input, and your goal is to output as many words as possible using those characters.

Input

• The characters will be one string
• Only the 26 letters of the alphabet will appear.
• Letters may appear more than once
• Letters can appear in any order. 5 e's might appear next to each other, and there might be other e's in the string.
• There will always be at least a single letter, but it might not always be possible to create a valid word

Example, using the letters from Scrabble:

eeeeeeeeeeeaaaaaaaaaiiiiiiiiioooooooonnnnnnrrrrrrttttttllllssssuuuuddddgggbbccmmppffhhvvwwyykjxqz

Output

A list of valid English words, which you can separate with a space, newline or comma. A trailing newline at the end is fine.

Default loopholes are forbidden.

code-golfwordnatural-language

---

Meta discussion (not apart of the question)

• Is code-golf a decent challenge for this? I'm more interested in more words being output than I am short code, but how best can I frame this challenge that the best result would be most words created and fewest characters left?
• Should I restrict the input list to just the letters from Scrabble? I mean how can I evaluate whether a program prints as many as possible?
• Should I provide a word list? I know there are challenges on this site where a word list is provided 1 and 2 and I'm sure there are a few others which I could not find.
• This is my third question, so any other feedback

Answer 13

Who's serving in table tennis?

Table tennis, also known as ping pong, is a well-known game in which players hit a ball back and forth across a table. One player serves the ball twice, and each time the ball is served, either player can score a point. Once the first player serves the ball twice, the second player gets to serve twice. Every two serves, the player which serves the ball switches. The game ends when one player has a score of 11 or more points and is two or more points higher than the other player.

Your task is to take the current score as input, and output a value depending on if player 1 should serve, player 2 should serve, or the game is over.

Input: The score of the first player to serve followed by the score of the other player. This can be as separate values or in a list, or another convenient data type.

Output: A distinct value for each possible case of output. For the test cases, I will use 1 to represent the player who serves first, 2 to represent the other player, and 0 to represent that the game is over.

Test cases:

player1score, player2score -> output

2, 0    ->  2
0, 0    ->  1
11, 0   ->  0
4, 4    ->  1
3, 2    ->  1
6, 9    ->  2
81, 82  ->  2
0, 29   ->  0
16, 13  ->  0

Answer 14

Help the library sort books

code-golf natural-language

A library needs to sort its books, located in separate sections by language. Of course, each language has its own rule for collating strings, so your method should handle that ability.

Most languages will want to treat titles case-insensitively, but unfortunately, the library has a section of Klingon books. And Klingon's romanisation, in case you don't already know, is case-sensitive. As a result, you need to give a way to have the sorter treat two given characters as the same.

Some of the titles also contain numbers, and you need to deal with those as well. Fortunately, the friendly people at the library have written some functions for you to deal with that, so all you have to do is take in a handle to a function as one of your inputs.

Your challenge: Sort a list of book titles, given a collating sequence and a function handle that converts a number to its string representation in the respective language.

• The collating sequence is a list of lists of strings. Given two strings A and B that appear respectively in the entries at indices i and j, respectively:
  • if i > j, then A should sort after B
  • if i = j, then A should sort the same as B
• In case some elements of the sequence have multiple characters, use the max-munch rule to tokenise the string: e.g. if both l and ll appear in the collating sequence, then lll should be tokenised to ll l.
• Any string of digits should be parsed as a number and passed to the callback. Each such string should be replaced by the result.
• Any characters not appearing in the collating sequence should be ignored. If two strings differ only by such characters, then sort them however you like.

Test cases

Assuming

english_letters = [["A", "a"], ["B", "b"], ["C", "c"], ["D", "d"], ["E", "e"], ["F", "f"], ["G", "g"], ["H", "h"], ["I", "i"], ["J", "j"], ["K", "k"], ["L", "l"], ["M", "m"], ["N", "n"], ["O", "o"], ["P", "p"], ["Q", "q"], ["R", "r"], ["S", "s"], ["T", "t"], ["U", "u"], ["V", "v"], ["W", "w"], ["X", "x"], ["Y", "y"], ["Z", "z"]]
arka_letters = [["t"], ["k"], ["x"], ["s"], ["n"], ["v"], ["f"], ["m"], ["d"], ["g"], ["p"], ["b"], ["h"], ["y"], ["c"], ["r"], ["z"], ["j"], ["w"], ["l"]]
function english_num_callback(num) {
  // convert a number to its representation in English
}
function arka_num_callback(num) { // handles nonnegative integers up to 9999
  if (num == 0) return "yuu";
  let kot = 0 | (num / 1000);
  let gal = 0 | (num / 100 % 10);
  let on = 0 | (num / 10 % 10);
  let ko = num % 10;
  let digits = ["yuu", "ko", "ta", "vi", "val", "lin", "kis", "nol", "ten", "los"];
  return (kot == 0 ? "" : digits[kot] + "kot") +
    (gal == 0 ? "" : digits[gal] + "gal") +
    (on == 0 ? "" : digits[on] + "on") +
    (ko == 0 ? "" : digits[ko]);
}

["Stack Exchange", "BB94 Channel!", "BB guns: all you wanted to know about them",
  "carrots", "A Grammar of Jbl", "69"], english_letters, english_num_callback =>
  ["A Grammar of Jbl", "BB guns: all you wanted to know about them", "BB94 Channel!",
    "carrots", "69", "Stack Exchange"]
["melidia", "diaklel", "44 miiko", "I Mess With the Librarians", "an isk ris tu lei",
  "lei e xion", "xagrisren et xep!", "on melkadren"], arka_letters, arka_num_callback =>
  ["xagrisren et xep!", "44 miiko", "melidia", "diaklel", "lei e xion",
    "an isk ris tu lei", "on melkadren", "I Mess With the Librarians"]

Answer 15

Will it be red sauce, brown sauce, or no sauce at all?

Unfortunately Danny Baker's Sausage Sandwich game has been taken off the air again, and I'm suffering from withdrawal already. Please alleviate my symptoms by writing a program or function to play the Sausage Sandwich game.

You need to guess how the target prefers to eat a sausage sandwich, given one of the three sauce options. Given an input positive integer n, then the following applies:

• There is a uniformly random 1 in n chance that the target chooses no sauce at all.
• Otherwise, there are equal chances of red sauce or brown sauce.
• However, if n is even, then there are n-1 remaining chances, which don't divide by 2. If you draw this n-1th chance you should consistently (for a given n) output the same answer. Please indicate how this is chosen in your answer.
• Output must consist of the phrases "red sauce", "brown sauce", or "no sauce at all", in any of lower, sentence, title or upper case.

This is code-golf, so the shortest program or function that breaks no standard loopholes wins.

Answer 16

Print the Golfican sequence

---

The Golfican sequence is a sequence of integers, \$u\$, defined as follows:

• If \$n\$ is a power of \$2\$, then \$u_n=\log_2n+1\$.
• If \$n\$ in not a power of \$2\$, then \$u_n=u_p\$, where \$p\$ is the number of numbers from \$1\$ to \$n\$ inclusive which are not powers of \$2\$.

So, the first numbers in this sequence are \$1,2,1,3,2,1,3,4\$ and so on. Your job is to write a program which takes a number, \$x\$, as input, and outputs \$u_x\$. This is code-golf, so the shortest program in bytes wins.

---

code-golf math

---

I couldn't find a corresponding OEIS sequence for this. Thoughts?

Answer 17

Posted

Answer 18

Optimize Grocery Bagging

code-golf combinatorics optimization

---

You've gone to the store and are at the checkout. Now since you want to be environmentally conscious (or are somewhere that charges for bags and want to save money), you've brought a few reusable bags and would like to minimize the number of plastic bags you use (There are no paper bags here).

Each reusable bag can carry 5 kg (5,000 grams) of groceries and each plastic bag can carry 2.5 kg (2,500 grams) of groceries. You will be given a list of weights of groceries (in whole grams) and a number of reusable bags and your task is to output a configuration of bagging that requires the fewest number of plastic bags.

Examples

• Input: 1 reusable bag, groceries: [150, 500, 800, 1250, 2000, 300, 550, 400, 750, 900, 1000, 600]
  • Output: Reusable[2000, 1250, 1000, 750], Plastic[600, 900, 550, 150, 300], Plastic[500, 800, 400]

More TBD

Rules and Assumptions

• Standard rules and loopholes apply
• Any convenient input or output method is acceptable as long as which bags are reusable is unambiguous in the output (without calculating anything).
• You may assume that there are no groceries larger than 2.5 kg. (No jugs of milk)
• All groceries listed require a bag. Unbaggable groceries will not be listed. (No hypothetical 24-packs of toilet paper)
• Any grocery item can be bagged with any other. (No need to worry about bread and cans of beans being in the same bag)
• Groceries cannot be split into multiple bags.
• There is no double-bagging.
• Complexity doesn't matter. There may be inputs that would require computation past the heat death of the universe to complete.

Happy Golfing!

---

Related

Sandbox: This could work as a restricted-complexity problem or fastest-code due to the naive solution being in \$O(n!)\$. Thoughts?

Answer 19

Beziér me a curve!

code-golf

Task: Create a program that will, given a number N, create a Beziér curve with N control points and output its equation.

The definition of a Beziér curve is $$ B(t) = \sum_{i=0}^n{{n\choose i}(1-t)^{n-i}t^iP_i} $$

Practically, this means that for a quadratic Beziér cuve: $$ B(2) = \sum_{i=0}^2{{2\choose i}(1-t)^{2-i}t^iP_i}\\ B(2) = {2\choose 0}(1-t)^2P_0 + {2\choose 1}(1-t)tP_1 + {2\choose 2}t^2P_2\\ B(2) = (t^2-2t+1)P_0 + 2(t^2-2t+1)P_1 + t^2P_2\\ B(2) = P_0t^2-2P_0t+P_0 + 2P_1t^2-4P_1t+2P_1 + P_2t^2 $$

where \$P_0\$ is the first control point, \$P_1\$ is the second control point and \$P_2\$ is the third control point.

Note that De Casteljau's algorithm may be useful.

Rules

• The input will be a number (string or number).
• The output will be a list of lists. Take an element \$l_n\$ of the top-level list. The elements of \$l_n\$ will be all the terms that, in the expanded form, are multiplied by \$P_n\$. -1t and t^1, as well as t^0 are all fine.
• Standard loopholes are not allowed.

Test cases

2:

[
  ["t^2", "-2t", "1"],
  ["2t^2", "-4t", "2"],
  ["t^2"]
]

5:

[
  ["-t^5", "5t^4", "-10t^3", "10t^2", "-5t", "1"],
  ["t^5", "-4t^4", "6t^3", "-4t^2", "t"],
  ["t^5", "2t^4", "t^3"],
  ["-t^5", "t^4"],
  ["t^5"]
]

The program with the shortest length wins. Be creative!

Answer 20

Reading the text of the millitext font

There is a font here that fits each character into a single, 1x5 pixel block. It does this (assuming you're using an LCD screen) by using the RGB channels of each pixel to expand the one pixel into three subcolumns, one for each channel. Your task is to take in a string of text that describes this font and return the correspond text encoded.

Millitext Alphabet

CHARACTER: 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ
ENCODING:  WYWBMRRMMMWYWYWWWMWBMRMYGYGYCWMMMMMW
           MGBWMRRMMMMMRMRRRMGBMRWMMMMMRGMMMMMB
           MGWWWWWBWWWYRMWWMWGBYRWMMYMYGGMMWGGG
           MGRBBBMBMBMMRMRRMMGBMRMMMRWMBGMCWMGR
           WWWWBWWBWWMYWYWRWMWWMWMMGRCMYGWBMMGW

I've abbreviated each color to a one character symbol (R=red, G=green, B=blue, C=cyan, Y=yellow, M=magenta, W=white).

Input Format

The input format for this is pretty open. You can have the input be an array containing each column, an array containing each row, a char[][], or anything like that. You can also choose to use the full words "red", "green", "blue", with uppercase/lowercase of your choice (but it must be consistent for each word! You cannot use "RED" and also do "green" or "Blue").

If your language happens to support it, you can also have input be colors (however that might work, I don't know off-hand).

You can assume that the input will ONLY contain encoded characters in the alphabet above (in particular, there will be no spaces or punctuation in your output).

Output Format

You can either output a string or some sort of character array. You can chose whether the letters are uppercase or lowercase, but they must all have the same case.

Example

MWRRGMGYRY
MRRRMMMMRM
WWRRMWMYRM -> HELLOWORLD
MRRRMWMMRM
MWWWGMGMMY

Rules

This is code golf, so shortest answer wins!

Test set

WYWBMRRMMMWYWYWWWMWBMRMYGYGYCWMMMMMW
MGBWMRRMMMMMRMRRRMGBMRWMMMMMRGMMMMMB
MGWWWWWBWWWYRMWWMWGBYRWMMYMYGGMMWGGG -> THEQUICKBROWNFOXJUMPEDOVERTHELAZYDOG
MGRBBBMBMBMMRMRRMMGBMRMMMRWMBGMCWMGR
WWWWBWWBWWMYWYWRWMWWMWMMGRCMYGWBMMGW

Answer 21

I Love U So Much!

Just print i love u, or I Love U.

But, because i love u so much, there is two rule.

1. At least there must be one I, and one U. Capital or not is regardless.
2. Every I and U must be stick together. No sole i and sole u.

This is code-golf, so shortest code with byte wins.

restricted-source code-golf

Answer 22

Trace My Triangles

Triangular is a 2D programming language that reads its code in the shape of the smallest triangle that the code will fit into, ignoring all whitespace. Its IP starts at the very top point of the triangle, and traverses the code starting in a Southeast direction. The IP's direction can be changed with the following directional switches (Note that "." is a no-op):

   ^
  ` /
 < . >  
  , \
   v

---

Challenge

You will be given a single input string p which represents a valid Triangular program. Your task is to write a program or function, which will print or return the actual execution order of p. Instructions in p which are never reached by the IP can be ignored.

You may assume the following:

• p will contain only characters which are necessary for a Triangular program to be valid; no need to account for whitespace.
• p will only switch directions via the directional switches listed above. The o,e,c and z instructions will not be used.

Examples

Input:                    Output:
---------------------------------------------------
F\(?)1/%-<                F(1<-%/?\)

,%./                      ,%/

\@~/;<                    \~<;/@

123456                    136

This is code-golf, so the shortest byte count wins.

---

Sandbox

• Is this a good idea for a question/not a dupe?
• Is the requirement clear enough?
• What other test cases should I be adding, if any?
• Should jump-related instructions - (, ) and ] - also be among the things that can be disregarded?
• Should any other sorts of instructions be disregarded?
• Would any other assumptions make this more manageable/fun?

Answer 23

I'm not able to find a challenge which will return as an integer how many days until Christmas based on an input like DDDD-MM-YY. So...

How many days until Christmas?

Work out the number of full days until Christmas based on today's date based on the Western Christianity date source.

Write a program, method, function, routine or sub-routine that accepts an input of the current date according the the Gregorian calendar source. The date may be in any format as long as you use the full year (so 2019-09-11 rather than 19-09-11). Other than requiring the full year, the date format is up to you (DD/MM/YYYY or MM/DD/YYYY or even formally written dates like Wednesday 12th June 2019). Please state what date format you are using in your answer.

An integer is displayed according to your standard output.

Example:

input -> output:

12/06/2019 -> 196 days until Christmas*
12/25/2019 -> 0 days until Christmas**

* DD/MM/YYYY format
** MM/DD/YYYY format

Answer 24

Is this set doubly orderable?

For input you are given a set of four or five sets of strings. Each string is at least two characters long; those first two characters are always digits but the remaining characters can also be letters.

The set of sets is doubly orderable if an ordered list can be constructed using one element from each member of the set such that:

• The first characters of each element of the list are in nondescending order
• The second characters of each element of the list are separately in nondescending order
• If any elements of the list have more then two characters, then those elements are all wholly equal with each other and appear at the beginning of the list (while still satisfying the other conditions).

Although there is an ordering on the list itself, the original sets can be sampled in any order necessary to achieve a valid list.

Example valid lists:

13  24  25  36
13e 13e 13  13
33s 37  37  37

Example invalid lists:

13  33  15  35  (first character not in order)
13  15  33  35  (second character not in order)
13e 24s 25  36  (different overlong strings)
33  37s 37s 37s (overlong strings are not first)

For output you should have:

• A consistent value indicating that the set is not doubly orderable
• A consistent value indicating that the set is can be doubly ordered using only 2-character strings
• A list of all overlong strings of which one is needed to make a valid list.

Full example:

1. 13 23 33 14 24 34 15 25 35 16 26 36 17 27 37
2. 33s 15e 16 17e
3. 34 25
4. 17e 37

In this example the 34 and 25 in set 3 force us to use either 33s or 15e from set 2 and therefore the 37 from set 4, with a number of options from set 1. Since all the valid lists begin with either 33s or 15e, these are the outputs.

Answer 25

Proving that a Russian cryptographic standard is too structured

Answer 26

Continue a progression code-golf math

The \$k\$th generalized mean \$M_k\$ of a set of numbers is defined as $$M_k(a_1,\dots,a_n)=\root^k\of{\frac{a_1^k+\dots+a_n^k}n}.$$ \$M_0\$, the geometric mean, is defined through a limit \$\lim_{k\to0} \root^k\of{\frac{a_1^k+\dots+a_n^k}{n}} = \root^n\of{a_1\cdot\dots\cdot a_n}\$. \$k\$ does not have to be integer.

An arithmetic progression is (according to Wikipedia) a sequence of numbers such that the difference between consecutive terms is constant. A geometric progression is a sequence of numbers such that the ratio between consecutive terms is constant.

There is a simple way to generalize these (that also explains why on earth is geometric progression named geometric): for a progression of order \$k\$ for any 3 consecutive elements \$a\$,\$b\$,\$c\$ \$M_k(a,c)=b\$. This way, the arithmetic progression is of order 1 and the geometric progression is of order 0. The order does not have to be integer.

The task is, given 3 real positive numbers \$a,b,c\$, to find the next term in the progression formed by them.

Notes

• If multiple valid outputs exist, you can output any of them.
• It is guaranteed that a valid output exists.
• An output is valid if \$|o_{correct}-o_{program}| \le10^{-5} \cdot \max(o_{correct}, 1)\$.

Sandbox stuff

• I still have to prepare some test cases, especially for non-integer orders.
• Has this been asked before?
• Do multiple correct outputs ever exist? I feel like very often there are infinitely many.
• Does Mathematica have a built-in?
• Should I add a time limit? I feel like brute-forcing all floating point numbers and checking if they are valid outputs might be shorter than actually calculating.
• Should I restrict the order to be integer, or even just 0 or 1 (leaving only arithmetic and geometric progressions)?
• Is there a simple and beautiful formula for the next term that I was unable to find and that all answers will have to copy from each other? I could neither get Mathematica nor myself to solve any related equations.
• Is the grammar correct enough?

Answer 27

Nearest match with limited values

code-golf

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When writing my solution for this challenge, I found that I needed to generate a target value using nothing but multiplication and increments/decrements, using a restricted set of values to use in the multiplication. Given that my choice of values was restricted, I had to brute-force what the optimum solution was. gObviously, this seems like a programming challenge!

The challenge is this: Given a target value t and set of allowed multiplier/multiplicand values, find the solution t=x×y±c (x and y are from the set of allowed values), that has the smallest value of c. If c is zero, indicate the solution as an exact match.

As this is a code-golf challenge, smallest code size wins. The standard rules apply.

Example program (ungolfed): Try it online!

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I don't think that I saw this particular challenge before, but I may have missed some. This is my first challenge, so please let me know how I can make it better!

Answer 28

Conversion

Assume that there is a number a. In every conversion of that number, the number can either convert itself to its value plus the value of one of its digits, or convert itself to its value minus the value of one of its digits.

In this situation, find the minimum number of conversions one has to make in order to get to the number b. If b cannot be reached, output -1.

Input

Input one line containing the integers a and b (where 1 <= a, and b <= 10^6).

Output

Output a line containing one integer, which represents the minimum amount that one has to convert the number.

Example input and output (s)

Input:  1 10
Output: 5

Why?

   1
-> 1+1=2
-> 2+2=4
-> 4+4=8
-> 8+8=16
-> 16-6=10
=> 10

Answer 29

Meta command-line flag parsing code-golf

The challenge

Write a program or function which determines whether or not a chosen command-line flag has been passed into the compiler or interpreter, but without accessing command-line parameters directly.

Details

• You must take in no input.
• You are free to choose the flag that is being detected, but it must:
  • be a flag, meaning a boolean command-line parameter that does not take any arguments (e.g. -O3 in gcc)
  • not print anything by virtue of being present (e.g. flags that print a version number or usage help are disallowed)
• The output must be 1 if the flag is present, and 0 otherwise.
• The program must successfully run without errors, whether or not the flag is present.
• You may not make use of the arguments passed to the compiler/interpreter, whether directly by value or by a property such as string length, array length.
• Separately from the chosen flag, other command line parameters can be used, so long as they remain the same when running the code with and without the flag in question.
• This is code-golf; shortest answer in bytes wins!

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Sandbox Questions

• Are there any other edge cases or loopholes that should be accounted for here?
• Is this a decision-problem, despite the challenge not being related to input?

Feedback welcome!

Answer 30

GPA calculator

A GPA is sort of weighted average based on the grades obtained in certain courses. There are a number of different systems, but for this challenge we'll use the following grades and their numeric values:

A: 4
B: 3
C: 2
D: 1
F: 0
P: —

The grade is P is a special case. For some courses, students can sign up to take a course as Pass/Fail. In the case of a Pass (P), the course has no effect on their GPA whatsoever, but in the case of a Fail (F), the course does affect the GPA.

All courses are weighted by the number of hours/credits they are taken for. So give the following transcript:

Course            Hours   Grade
------            -----   -----
Next Gen Perl       6       A
Advanced C-minar    1       C
Starting with Java  3       B

We would calculate the total points as 35 (6*4 + 1*2 + 3*3), and then divide it by the number of hours, or 10 (6+1+3) for a final GPA of 3.5. If Starting with Java had been given an F, the total points would be 26 with 10 hours, for a GPA of 2.6. However, if it had been a P, the total points would still be 26, but with only 7 hours, the GPA would be 3.71428571429…

Input

An arbitrarily long list/array/sequence/etc of transcript entries. The entries are simply a two item list/array/sequence/etc with one item being an integer value (doesn't have to be an actual Int value, floats are fine) of hours, and the other being the string ('A','B'...). The above example would have been:

[
  [6, 'A'],
  [1, 'C'],
  [3, 'B']
]

You may assume that the list will have at least one computable grade (so no empty transcripts, nor transcripts consisting only of P). If your language does not have strings, then you may use numbers for A/B/C/D/F/P, but their values must be similarly spaced (e.g. 10,11,12,13,14,25)

Output

A number representing the GPA (float or other non-Int value)

Scoring and Restrictions

Codegolf, so shortest code in bytes wins. Standard rules apply.

Sandbox questions

I thought about allowing for either +/- grades (A+, A, A-, B+...) which would definitely prevent using ASCII values as easily, but then that led me to the thought of having a second input which is a list of possible grades with their equivalent value, but I think that would start over complicating it and way over benefit languages with built-in hashing. Thoughts?