Sandbox for Proposed Challenges

Question

What is the Sandbox?

This "Sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to the main page. This is useful because writing a clear and fully specified challenge on 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.

To post to the Sandbox, scroll to the bottom of this page and click "Answer This Question", or click on the "Add Proposal" link below. Click "OK" when it asks if you really want to add another answer. Write your challenge just as you would when actually posting it. You may also add some notes about specific things you would like to clarify before posting it. Other users will help you improve your challenge by rating and discussing it. When you think your challenge is ready for the public, go ahead and post it, and replace the post here with a link to the challenge and delete the Sandbox post.

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Answer 1

Heads I win, tails you booze: coin tossing, pub trivia style code-golf probability-theory game

At my old pub trivia night, a free jug of beer or bottle of wine was awarded to the team that won Heads or Tails. This game requires players to correctly guess the outcome of successive coin tosses. The game proceeds as follows:

1. Before each toss the remaining players, who are standing, place both hands on their head (for heads) or their bottom (for tails). If all remaining players choose the same outcome (which would lead to a draw) the host refuses to toss the coin until at least one player changes his/her guess.
2. The host then tosses a coin (assumed fair) and announces the outcome. All players who guessed incorrectly are eliminated and have to sit down.
3. Play continues until there is only one person left standing to claim the prize for their team.

In perfect play, the remaining players on each team always divide as evenly as possible between heads and tails:

• If the number of remaining players on a team is \$2k\$ for some positive integer \$k\$, then exactly \$k\$ of them guess heads and \$k\$ of them guess tails.
• If the number of remaining players on a team is \$2k+1\$, then with equal probability
  • exactly \$k\$ of them guess heads and \$k+1\$ of them guess tails, or
  • exactly \$k+1\$ of them guess heads and \$k\$ of them guess tails.

An interesting consequence of players not acting independently is that a team's probability of winning is not, in general, equal to \$\dfrac{\text{number of players on the team}}{\text{number of players on all teams}}\$, as the examples below illustrate.

Challenge

Assume that there are \$n_0\$ players on our team and \$n_1, n_2,\ldots, n_N\$ players on the opposing \$N\$ teams (\$N\$ and the \$n_i\$ are all positive integers). Given the \$n_i\$ as input, write the shortest program or function that calculates the probability that our team wins the booze, assuming perfect play by all teams.

Input format is flexible: you may (for example) take

• an integer \$n_0\$ and a list \$[n_1, n_2, \ldots, n_N]\$ (this format is used in the test cases),
• a flat list \$[n_0, n_1, \ldots, n_N]\$,
• a nested list \$\left[n_0, [n_1, n_2, \ldots, n_N]\right]\$.

The \$n_i\$ may be taken in any order. Output should be in a suitable numeric format. Floating-point approximations are acceptable provided that the underlying algorithm is theoretically exact. You may not return a list of winning probabilities for all teams (I don't care how likely it is that another team wins).

Examples

Example 1: \$n_0=1\$, \$n_1=2\$

Suppose there are only two teams: our team has one player and the opposing team has two players. After the first toss, exactly one player from the opposing team remains in the game (because one player guesses heads and the other guesses tails). For our team:

• Half of the time, our player has guessed incorrectly and is eliminated. The other team wins.
• Half of the time, our player has guessed correctly. A second toss occurs—a head-to-head battle with the remaining player on the other team—which our player wins half of the time.

The probability that our team wins is therefore \$\dfrac{1}{2}\cdot0 + \dfrac{1}{2}\cdot\dfrac{1}{2} = \dfrac{1}{4}\$.

Example 2: \$n_0=2, n_1=3\$

In this case, both teams survive the first toss. Exactly one player remains on our team. For the other team:

• Half of the time, one player remains. A second toss decides the winner.
• Half of the time, two players remain. From this point, the remaining tosses play out exactly as in Example 1.

The probability that our team wins is therefore \$\dfrac{1}{2}\cdot\dfrac{1}{2} + \dfrac{1}{2}\cdot\dfrac{1}{4} = \dfrac{3}{8}\$.

Test cases

\$n_0\$, \$[n_1, n_2, \ldots, n_N]\$ -> Output

1, [2] -> 1/4
2, [3] -> 3/8
5, [5, 5, 5] -> 1/4
5, [3, 5, 7] -> 5929/24576
8, [1, 2, 4] -> 485/768
6, [4, 5, 5, 6, 8] -> 45/256

Answer 2

Score an approximation code challenge code-golf

Given a list of inputs (strings) and their expected outputs (integers or floats)^[1], and a black-box program^[2], calculate the score using the following scoring system:

Let \$R_n\$ be the expected output of the \$n^{th}\$ input, let \$A_n\$ be the actual output given by the black-box program, and let \$ j \$ be the total number of input/output pairs. (All values are positive and non-zero)

Then the score is defined as: $$S=\left\lceil L\times\max_{1\le i \le j}\left({\max\left(\frac{A_i}{R_i},\frac{R_i}{A_i}\right)^2}\right)\right\rceil$$ where \$L\$ is the length of the black-box program in bytes.

Example:

If the size of the program is \$100\$ bytes and the worst approximation is on the input "moon", where the program outputs \$1000\$ instead of the expected \$1737\$, then the score would be:

$$S=\left\lceil 100\times{\left(\frac{1737}{1000}\right)^2}\right\rceil=302$$

This system is taken shamelessly from this challenge by @Arnauld. Here is his reference implementation.

---

[1]: You may take the inputs and outputs either zipped ([(in1, out1), (in2, out2), ...]), or not zipped (([in1, in2, ...], [out1, out2, ...]), with both lists of the same length), at your option.

[2]: You may take the black-box program as either:

• a black-box function, and its length in bytes, as two separate inputs
• a string of code to be evaluated, as one input (the length will not be given separately unless necessary)

Rules

• You may use any sensible I/O method
• Standard loopholes are forbidden
• This is code-golf, so the shortest code in bytes wins.

Answer 3

Stack half full or half empty? (worldview of a programming language)

Is the glass half full or half empty? It's a common rethoric question to determine a person worldview, which can be optimistic or pessimistic based on the answer given. If i were dealing with a machine i would probably ask "Is the stack half full or half empty?" Let's try and see if programming languages have a worldview too.

Write a full program or a function which prints or returns one of "The stack is half full." or "The stack is half empty." when given as input the question "Is the stack half full or half empty?" but wait.. you have to provide a stack to be observed.. which stack you provide is up to you: input one or check an already existing stack. Your solution will then output one of the two sentences mentioned above for a non empty / non full stack, your choice which one to print, just make sure your answer is as short as possible because this is code-golf. For an empty stack it must produce the "empty" output while for a full stack "full".

Survey

I will make a chart of the pessimistic Vs optimistic languages based on the half outputs. If you find the same byte count for both choices you can provide both, in which case they will count on both sides of the chart, but you just can select one if you like.

input

• A sentence in any reasonable method.
• The behavior is defined only for the question "Is the stack half full or half empty?" and exactly this.
• Indeed your solution can also completely ignore the input as long as it works with the specified input.
• Question mark is mandatory.

output

• One of "The stack is half full." or "The stack is half empty.", for a non full / non empty stack.
• "full" or "empty" for a full stack or an empty stack respectively
• upper / lower case or a mix are fine.
• ending dot not mandatory.

Rules

• Only the mentioned input allowed.
• Loopholes allowed.
• This is code-golf and the answer with the fewer bytes of source code wins.

Answer 4

Bytewise look-and-say sequence code-golf

The look-and-say sequence is a sequence which begins with 1, 11, 21, 1211, 111221, 312211. To get a term of the sequence from the previous, read the previous out literally:

312211 => one three, one one, two twos,two ones => 13112221

So the next term is 13112221.

Given this javascript code (Node.js), which outputs the look-and-say sequence indefinitely, delimited by newlines:

function nextTerm(x){
  return x.replace(/(.)\1*/g,z=>z.length+z[0])
}
function printUpTo(x){
  var str = '1';
  for(var i = 0; i < x; i++){
    console.log(str);str = nextTerm(str);
  }
}
printUpTo(Infinity)

It will output a string that begins 1\n11\n21\n1211\n111221 etcetera. Your job is to write a function that takes a number as input and outputs that byte of the output string.

Rules

You may output a different character for newline instead of \n, e.g. # or something.

Scoring

Your program should be able to handle 100 million.

The first answer to handle 1e+18 correctly will receive a 100-rep bounty. This cannot be hard-coded.

Standard loopholes apply.

Test cases:

1 => \n
5 => 2
10 => 1
20 => 3
50 => 3
100 => 1
1000 => 1
100000 => 3
10000000 => 1

This is code-golf, so shortest bytes wins.

Answer 5

Self improving program

quine code-golf restricted-complexity

In this challenge you will write a program or function which when run will output a faster solution to this challenge.

Formally speaking: you will write a program or function, \$T_0\$, which takes an integer \$x\$ as input and outputs a program or function (in the same language), \$T_1\$, which is itself a valid solution to this challenge, such that there exists a function \$f\$ where \$T_1\$ is in the time complexity class \$O\left(f\right)\$, but \$T_0\$ is not. That is to say the output program must have a strictly faster asymptotic time complexity.

Note that since \$T_1\$ must be a valid solution to the challenge it must output a program or function \$T_2\$ which is even faster, and so on and so forth, creating an infinite chain each faster than the last.

Answers will be scored by their length in bytes with fewer being better.

---

Precision

In keeping with the tradition of this site, and to remain inclusive: The order notation of a function will be assumed to be measured by the algorithm implemented by your answer. Thus we will pretend not to notice the behavior of your actual program for inputs out of the range of your language's numeric type.

However that being said, in order to ensure that you are actually changing the algorithm at every step, for constants initialized in your program this leniency is not given. e.g. If you use a double precision floating point 1.0000000000000001 is equal to 1.0. So if your method relies on an increasing or decreasing constant embedded in the program you should be careful that the algorithm actually changes.

Simply put for \$T_n(x)\$ you are forgiven for errors arising from very large \$x\$, but not from very large \$n\$.

Answer 6

Posted at Convert Gemtext to HTML but moved here to discuss

Gemtext is a very simple markup format used by the alternative web protocol Gemini. Write a Gemtext to HTML converter.

From the Wiki:

A line of text is a paragraph, to be wrapped by the client. It is is independent from the lines coming before or after it.

A list item starts with an asterisk and a space. Again, the rest of the line is the line item, to be wrapped by the client.

A heading starts with one, two, or three number signs and a space. The rest of the line is the heading.

A link is never an inline link like it is for HTML: it’s simply a line starting with an equal-sign and a greater-than sign: “⇒”, a space, an URI, and some text. It could be formatted like a list item, or like a paragraph. Relative URIs are explicitly allowed.

Example:

# This is a heading 
This is the first paragraph.
* a list item
* another list item 
This is the second paragraph.
=> http://example.org/ Absolute URI
=> //example.org/ No scheme URI
=> /robots.txt Just a path URI
=> GemText a page link

This should produce this HTML tree (just the equivalent tree, not the exact formatting):

<h1>This is a heading</h1>
<p>This is the first paragraph.</p>
<ul>
<li>a list item</li>
<li>another list item</li>
</ul>
<p>This is the second paragraph.</p>
<a href="http://example.org/">Absolute URI</a>
<a href="//example.org/">No scheme URI</a>
<a href="/robots.txt">Just a path URI</a>
<a href="GemText">a page link</a>

HTML in the text must be escaped, e.g paragraph <p> is cool becomes <p>paragraph &ltp&gt is cool</p>.

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

Answer 7

Dedekind, cut!

Objective

Given a Dedekind cut and a nonnegative integer \$n\$, print the real number represented by the Dedekind cut up to \$n\$ precisions, rounded.

Dedekind cut

A Dedekind cut representing a real number \$x\$ is a boolean-valued function on \$\mathbb{Q}\$ that gives a falsy value for rational numbers under \$x\$, and a truthy value otherwise.

Note that Dedekind cuts can represent arbitrary real numbers. Irrational, nonconstructible, transcendental, or even uncomputable numbers.

Rules

• Direction of rounding is implementation-defined.

• For the inputted Dedekind cut, it shall accept arbitrary rational numbers. That is, the numerator and the denominator must be arbitrary-length integers. (Though the denominator is nonzero, of course) Accepting the rational number as a pair of integers is acceptable. In this case, the denominator is expected to be positive, and the fraction is expected to be irreducible.

• Invalid inputs fall in don't care situation. This also applies to the rational numbers the Dedekind cut accepts.

• Note that negative numbers also must be handled. For nonnegative numbers, however, it is implementation-defined whether to output a leading plus sign.

• Outputting leading or trailing whitespaces is permitted.

• All digits after the decimal point shall be considered significant in this regard. The amount of significant digits after the decimal point must be exactly \$n\$. Trailing zeros cannot be discarded.

• If \$n = 0\$, the decimal point may be omitted.

• If the decimal representation has no significant digits before the decimal point, the leading zero may be omitted.

• The omission from the previous two rules cannot be present simultaneously.

Examples

• For \$x = 0\$ and \$n = 0\$, output one of 0, 0., +0, and +0..

• For \$x = 0\$ and \$n = 2\$, output one of .00, 0.00, +.00, and +0.00.

• For \$x = ½\$ and \$n = 0\$, output one of 0, +0, 1, +1, 0., +0., 1., and +1..

• For \$x = ½\$ and \$n = 3\$, output one of .050, 0.050, +.050, or +0.050.

• For \$x = \sqrt{2}\$ and \$n = 3\$, output either 1.414 or +1.414.

• For \$x = -\pi\$ and \$n = 3\$, output -3.142. Note the rounding.

Ungolfed solution

Haskell

An implementation with exponential time complexity.

import Text.Printf

showDedekind :: (Rational -> Bool) -> Int -> String
showDedekind x n = go (0.5 * 10 ^^ negate n)
  where
    go p = let
        epsilon = 10 ^^ negate n
        in if x p
            then if x (p - epsilon)
                then go (p - 2 * epsilon)
                else let
                    str = printf "%0*d" n (floor (p / epsilon) :: Integer)
                    (str1, str2) = splitAt (length str - n) str
                    in str1 ++ '.' : str2
            else go (p + epsilon)

Answer 8

Let's rise higher!

answer-chaining, number, restricted-source

(I am posting this challenge in sandbox because this kind of exceptional challenges are often closed, and then downvoted to oblivion, so I want to get your feedback and with kind help you fix the specifications in this challenge, and make it interesting, Thanks!)

---

Challenge

The main objective of the challenge is pretty simple, this is an answer chaining contest, where you have to serially print numbers from 1. That means User 1's answer will print 1, then User 2's answer will print 2 and so on. But there are some rules to make the contest tougher.

Rules

• You can't use the characters of the source code used in the previous answer.

• Each answer cannot use more than 12 distinct bytes.

• Use of comments in your code is disallowed.

• You cannot post 2 answers in a row, let me explain, suppose you have written answer no. 5, now you cannot write answer no. 6, you have to wait someone to post a valid answer no. 6 (That prints 6 without using characters in answer no. 5), and after that you can write a valid answer no. 7 following the rules.

• Program cannot take input or access internet.

• Standard loopholes apply.

Scoring criterion

This is not code-golf challenge, so there is a custom objective scoring criteria. Try to make your score higher.

• Each answer's initial score is 1. (Only chain beginning answer has score 0).

• For each distinct byte you use, your score is increased by the number of distinct bytes. That means if your number of distinct bytes is 6, then your score increases by 1+2+3+4+5+6, and if your number of distinct bytes is 7, then your score increases by 1+2+3+4+5+6+7 and so on.

• You have to calculate distinct byte difference with the previous answer, and add/subtract score using the 2nd rule. So if byte difference is 3 then you will get a +1+2+3 score, or if -3 (Previous answer has 3 more distinct bytes than yours), then -1-2-3.

• For first 40 bytes you will get a 0.15 score, but from then you have to minus 0.5 score. An example if your score has total 45 bytes then your score bonus will be (40*0.15)-(5*0.5)=6-2.5=3.5, so you have to add +3.5 to your score. (The score criteria is to encourage medium length smart answers.)

A total example:

Suppose,

• Your previous answer has 4 distinct bytes, and a total of 20 bytes
• Your answer has 7 distinct bytes, and a total of 56 bytes

So your score will be:

Distinct byte difference: (7-4)=3
Total score: 1+(1+2+3+4+5+6+7)+(1+2+3)+(40*0.15)-(16*0.5)=33

So you get a score of 33 for this condition.

Answer format

# Answer Number. Language Name, x Bytes, y Distinct bytes, Score: Z

    source code

(TIO/Any other interpreter link) -> Not required, but preferred

example

1. Powershell, x Bytes, y Distinct Bytes, Score: Z

......

Winning criterion

Winner will be determined after 30 days, winner is determined by total score. But users are welcome to continue the chain after that!

Suppose you have three answers with score 33,16,78 then your total score will be 33+16+78=127.

And there is two special prizes from me after 30 days:

• +150 bounty for the winner.
• +50 bounty for the single answer with highest score! (Such as man of the match in Cricket)

Chain beginning answer:

---

1. PowerShell, 1 byte, 1 distinct byte, Score: 0

1

Try it online!

---

Meta

• Are all rules clear?

• Please improve the scoring criterion and rules. (Especially please improve the second rule, I am not very sure about that.)

• Please make me a javascript snippet for leaderboard, to sort users by their total score.

• Any other feedback please.

Answer 9

Finish what John McCarthy started (WIP) code-golf interpreter lisp

This does not have anything to do with Joseph McCarthy or communism. Some background from Wikipedia (you can skip ahead if you like):

John McCarthy published the first paper on Lisp in 1960 while a research fellow at the Massachusetts Institute of Technology. In it he described a language of symbolic expressions (S-expressions) that could represent complex structures as lists. Then he defined a set of primitive operations on the S-expressions, and a language of meta-expressions (M-expressions) that could be used to define more complex operations. Finally, he showed how the meta-language itself could be represented with S-expressions, resulting in a system that was potentially self-hosting.[3] The draft version of this paper is known as "AI Memo 8".^[4]

Example M-expressions

McCarthy had planned to develop an automatic Lisp compiler (LISP 2) using M-expressions as the language syntax and S-expressions to describe the compiler's internal processes. Stephen B. Russell read the paper and suggested to him that S-expressions were a more convenient syntax. Although McCarthy disapproved of the idea, Russell and colleague Daniel J. Edwards hand-coded an interpreter program that could execute S-expressions.2 This program was adopted by McCarthy's research group, establishing S-expressions as the dominant form of Lisp.

Task

Interpret a subset of M-expressions, where 9 primitive functions have already been defined.

Syntax

Atoms: An atom is a series of any characters excluding [, ], ;. While an atom name can include whitespace, leading and trailing whitespace is ignored. Some examples include foo, lambda (also a function name), and nil (also a list). Atoms act as both variables and data (they're like strings).

Booleans: The atom t is truthy, whereas the atom nil is falsy.

quote: A series of expressions between square brackets, delimited by semicolons. [a; [b; c]; de] is equivalent to the S-expression (QUOTE (A (B C) DE)). It is somewhat like this JS list: ["a", ["b", "c"], "de"].

cond: A series of if-then pairs between square brackets, delimited by semicolons, with an arrow -> (you can use any other character(s)) separating the if-then pairs. e.g. [atom[x] -> x; t -> car[x]] yields x if it's an atom, or the first element of x if it's a list. It is guaranteed that at least one of the cases will be true.

Function application: Functions can be called using functionname[arg1; arg2; ...; argN].

• car - Return the first element of its argument.
• cdr - Return its argument without the first element.
• cons - Prepend its first argument to its second argument.
• eq - Check if its two arguments are equal.
• atom - Check if its argument is an atom.
• lambda - Define an anonymous function using the syntax lambda[[param1; param2; ...; paramN]; bodythatusesparams].
• label - Store a function using a name. For example, label[drop2; lambda[[xs]; cdr[cdr[xs]]]] defines a function drop2 that drops the first two elements of its first argument.

Rules

• Functions may use lexical or dynamic scope, or some crazy mixture of both.

_{Much of this question is copied from this challenge and the Wikipedia article on M-expressions.}

Questions for Meta

• For cond, should I use the [condition -> res; condition2 -> res2; ...] syntax, or should I keep it like the linked challenge?
• Should answers support higher-order functions?
• Does anyone have any good examples using Mexprs?

Answer 10

Hello, Permutations!

Answer 11

I ain't no Fortunate sum

Answer 12

Uppercase JSON member names

Given a single valid JSON value, uppercase all member names. That is, you must also return valid JSON that encodes an equivalent value, except that all names of members in all objects, have been converted to uppercase according to one of the Unicode methods (simple or full).

Details:

• The given value can be null, a number, a string, an array, or an object. There may therefore not be any names to convert, but such names can also "hide" as elements/members of arrays/objects in arrays/objects, …

• Dictionaries are considered unordered.

• Names and strings will only encode ASCII.

• Keys will be unique, even after case conversion.

• Floating point imprecision is tolerated.

Example input A

["a\":",{"b":"c"}]

Example outputs

["a\":",{"B":"c"}]

[
  "a\":",
  {
    "B" : "c"
  }
]

Example input B

{"h\u0065re":
"are'=",    "be"
:{"dra\u0000gons":true,"b\\e\"ar\ns":"two"},"\t":[1e-0,null,3e+2
,  {"":""} ,{
},
"name\":\"value",[false,[],[[]]]]}

Example outputs

{                      
 "BE": {               
  "B\\E\"AR\nS": "two",
  "DRA\u0000GONS": true
 },                    
 "HERE": "are'=",      
 "\t": [1,             
  null,                
  300,                 
  {                    
   "": ""              
  },                   
  {                    
  },                   
  "name\":\"value",    
  [false,              
   [],                 
   [[]]]]              
}

{"BE":{"B\\E\"AR\nS":"two","DRA\u0000GONS":true},"HERE":"are'=","\t":[1,null,300,{"":""},{},"name\":\"value",[false,[],[[]]]]}

code-golf string parsing unicode conversion

Answer 13

Minimally Making Change

Answer 14

Find the Best Set of Adapters

Moved here: Find the Best Set of Adapters

Answer 15

Fortuitous Numbers

Four is Magic is a very interesting math game.

1. We start out with a number: 1
2. We spell it into English: “one”
3. We find the sum of the letters: 3
4. Go back to step 2, until the game ends at “4”

The reason “4” is Magic, is that “Four” has 4 letters, and no other number has this property.

---

Fortuitous Numbers

In this game, I’m making one change.

1. Take for example the number: 24.
2. Write it out in English: “twenty four”
3. Note that there are 2 words
4. Take the product of the word lengths
5. 24 - “twenty four” - 6 * 4 = 24

4 and 24 are Fortuitous Numbers. Are there any more?

---

The challenge

Your challenge is to create a piece of code that will generate all Fortuitous Numbers.

Specifically:

1. Solutions should be found by the program, not chached by you.
2. We never say, “one hundred and one”. Exclude the “and”
3. The only output should contain a comma separated list of only the solutions:

4,
24,
n,
m,

4. The code should have no limit as to how large the number can go. If you have trouble finding names, used the ones mentions in this Wikipedia article. This will take you smoothly to 10³⁰⁰³ and beyond.
5. Hint: Look at the sequence, A058230.

---

Bonus!

1. Program generates the first 9 solutions relatively quickly (under 5 minutes time.)
2. Program also finds Fortuitous Numbers if type a -> b -> ... -> a instead of just a -> a

Answer 16

What's missing code-golfstringdecision-problem

Write a program which takes two arrays of strings as input. One of them (your choice which) will have one item missing compared to the other. Your program must figure out what is missing.

Rules

You can choose which array has one missing.

The arrays may be scrambled. (see testcases #3 and #4)

Testcases

["hello","world"] , ["hello"] => "world"
["Hello","Hello","Hello"], ["Hello","Hello"] => "He
["a","b","c","b","a"], ["c","b","a","a"] => "b"
["d","d","p","i","h"], ["p","i","d","d"] => "h"

This is code-golf, shortest bytes wins!

Answer 17

ROT47(code) code-golfciphersource-layout

ROT13 is a Caesar cipher where every letter is replaced by the 13th letter that follows it in the alphabet.

Every letter and its counterpart:

a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z
n	o	p	q	r	s	t	u	v	w	x	y	z	a	b	c	d	e	f	g	h	i	j	k	l	m

ROT47 is a deritave of ROT13 which includes all the ASCII printable characters except space. Rot47 substitutes every character with the 47th character that follows it in the ASCII range.

Every character and its counterpart:

!	"	#	$	%	&	'	(	)	*	+	,	-	.	/	0	1	2	3	4	5	6	7	8	9	:	;	<	=	>	?	@	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z	[	\	]	^	_	`	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z	{	|	}	~
P	Q	R	S	T	U	V	W	X	Y	Z	[	\	]	^	_	`	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z	{	|	}	~	!	"	#	$	%	&	'	(	)	*	+	,	-	.	/	0	1	2	3	4	5	6	7	8	9	:	;	<	=	>	?	@	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O

I ROT47( your code) and you ROT47( the output)

• Your code is supposed to at least output 1 character within the [33,126] ASCII range.
  
• When ROT47 is applied on your code, the output should also be ROT47 of the previous output
• solve in the fewest bytes possible

Below a ROT47 converter taken from decode

var input = document.getElementById("input");
var editor = CodeMirror(input, {
    lineNumbers: true,
    tabSize: 2,
    mode: 'javascript',
    theme: 'monokai'
});
editor.setSize(900, 100);
document.getElementById("button").onclick = function(){
  editor.setValue(rot47(editor.getValue()));
}


//implementation below from https://www.dcode.fr/rot-47-cipher
// Javascript
function rot47(x){
 var s='';
 for(var i=0;i<x.length;i++){
  var j=x.charCodeAt(i);
  if((j>=33)&&(j<=126)){
   s+=String.fromCharCode(33+((j+14)%94));
  }
  else {
   s+=String.fromCharCode(j);
  }
 }
 return s;
}

<head>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta content="utf-8" http-equiv="encoding">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.60.0/codemirror.min.css" integrity="sha512-xIf9AdJauwKIVtrVRZ0i4nHP61Ogx9fSRAkCLecmE2dL/U8ioWpDvFCAy4dcfecN72HHB9+7FfQj3aiO68aaaw==" crossorigin="anonymous" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.60.0/codemirror.min.js" integrity="sha512-hc0zo04EIwTzKLvp2eycDTeIUuvoGYYmFIjYx7DmfgQeZPC5N27sPG2wEQPq8d8fCTwuguLrI1ffatqxyTbHJw==" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.60.0/theme/monokai.min.css" integrity="sha512-R6PH4vSzF2Yxjdvb2p2FA06yWul+U0PDDav4b/od/oXf9Iw37zl10plvwOXelrjV2Ai7Eo3vyHeyFUjhXdBCVQ==" crossorigin="anonymous" />
</head>
<body style="background-color:#333333
">
<div id="input">
</div></br>
<button id="button" style="background-color: #17202a
;color:white">ROT47</button>
</body>

---

Meta questions:

• Is it an interesting challenge?
• Is the explanation clear?
• suggestion for a title.

Answer 18

To count the sum of all Unicode characters of a given input under an interesting constraint

Answer 19

Sum of two squares

code-golf math number-theory decision-problem

Given an integer \$n\$, determine whether \$n\$ can be expressed as the sum of two square numbers, that is \$\exists a,b\in\mathbb Z|n=a^2+b^2\$.

   0 -> truthy
   1 -> truthy
   2 -> truthy
   3 -> falsy
   4 -> truthy
   5 -> truthy
   6 -> falsy
   7 -> falsy
  11 -> falsy
9997 -> truthy
9999 -> falsy

Relevant OEIS sequences:

• A001481 - should return truthy
• A022544 - should return falsy

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

Related, related.

Answer 20

Irreducible Rube Goldberg Sort (WIP)

sorting code-challenge

---

You are given a list containing at least 10 integers. You must sort them in the most complicated and roundabout way possible.

Your task is to write \$n\$ programs (or functions) which, when combined in a specific constant sequence (specifically, feeding the output of the current step into the input of the next step), result in a sorted version of the original list. This sequence of programs should be set up in such a way that the system will not work if any subset of steps is removed. (for example, compressing and decompressing the stream, roundabout encryption that cancels itself out, etc...)

Your score is \$n\$. Highest score wins.

Rules, Clarifications, and Notes

• Standard rules and loopholes apply
• Any method of I/O is fair game. It does not need to be consistent across all programs/functions.
• You may use any number of programming languages to solve the problem.
• It should not take an unreasonably long time to sort a list of up to 1000 elements using your system of programs. It should be reasonable to run it from start to finish during a lunch break (30 minutes)
• Lists can contain any integer from -999,999,999 to 999,999,999, inclusive, and may contain indistinguishable duplicates.
• Your system of programs should work for lists of any size if given enough time and space.

Answer 21

Ball game KoTH

Answer 22

Dominate a zero-sum game

Answer 23

Write a rectangular code that takes a rectangular input and output it. If the code is repeated horizonally and vertically for times, output the input rectangular repeated for same amount of times.

Take an example, if your submission is

CODE
HERE

, then program

CODECODECODECODE
HEREHEREHEREHERE
CODECODECODECODE
HEREHEREHEREHERE

inputting

01
23
45

should output

01010101
23232323
45454545
01010101
23232323
45454545

Answer 24

Create a C program that is less than 120 characters the produces the most ASM possible.

This limit does not include the def of main, or including headers. If a function is called the chars in the function count toward limit. The same goes for macros. The compiler used will be GCC 10.2 -O3 targeting x86-64.

The code conforms to these parameters and produces the most instructions wins.

I have a few questions regarding this. Is the character limit too limiting? Is the choice of compiler a good one? Is the optimization level being -O3 a good idea? Please share any other thoughts you have.

Thanks

Answer 25

KotH: Assembly Anarchy

Draft. Just posting this so I don't forget I had this idea. Feel free to suggest improvements to the general idea here.

Basically, there would be a computer with memory and a processor. Programs would be submitted in a custom assembly language, and they would try to run a function (their flag) as many times as possible. They could try to interfere with other programs, by doing things like replacing the pointer to another bot's flag with their own, or preventing other bots from being run.

Answer 26

Poor Man's DRM

Write a program that only prints Welcome at the first execution and first execution only. All executions after the first execution should only print Where money.

Anything is allowed as long as the following condition is met: An execution ends after the program exits. So the second execution can only start after the first execution exits completely.

code-golf

---

Reason for the condition: to prevent submissions that linger around in the memory and keep a runtime counter.

Answer 27

Cooperative counting

Answer 28

Multiplicative Persistence #2

Answer 29

Find the traitor cops-and-robbers (WIP)

In this challenge, the cops are the robbers/moles and the robbers are the cops/investigators.

Cops

Cops will write a program that will output one of the following strings:

• "Hello World!"
• "Totally not evil stuff"
• "Good morning"
• "Innocent things"

However, when n specific characters are removed, where 0 < n < length of cop's program, the resulting program should output one of the following strings:

• "Bye World!"
• "Top secret stuff"
• "Evil things"
• "Horrible morning"

Cops will reveal the original program and n, but not the resulting program. They will also reveal the 2 strings that must be outputted by the original and transformed programs.

A cop's score is \$\binom n r\$, or \$\frac{n!}{r!(n-r)!}\$, where \$r\$ is the size of the cop's program and \$n\$ is the number of characters to be deleted. The lower the score, the better.

Rules

• The original and transformed program may output in different ways, as long as the cop specifies what they are.
• The characters to be deleted do not have to be adjacent.

Robbers

Robbers must find a way to make the cop's program output the chosen 2nd string by removing any n characters (not necessarily the same as the cop's).

Example cop

Python, n = 1

a = ["Totally not evil stuff", "Hello World!"][01]
print(a)

The original string is "Hello World!", and the transformed program prints "Totally not evil stuff".

Example robber

Python, cracks Foobar's answer

a = ["Totally not evil stuff", "Hello World!"][0]
print(a)

Deleting the 1 at the end of the first line prints the target string.

Questions for Meta:

• Which original and transformed strings should I use?
• Is this a duplicate?

Answer 30

Exchange of money in least notes

Suppose A and B are two good friends. A has borrowed \$n\$ dollar from B. Now B wants the money back from A and A is also ready to give it. But the problem is A has only \$x\$ dollar notes and B has \$y\$ dollar notes. They both want to keep the number of notes in exchange as low as possible.

As an example if \$n=37\$, \$x=5\$ and \$y=2\$, then the least amount of notes in exchange will be nine 5 dollar noted from A then four 2 dollar notes from B will make 37. This solution is found through brute forcing with a python program.

Here in the challenge your input will be values of \$n, x, y\$ and output should be the least of amount of notes as possible for A, B. A will give notes first and B later. Input and output seperator can be anything, no leading zeros in input numbers, no negative numbers in input. Standard loopholes apply and shortest code wins.

Test Cases

37 5 2 -> 9 4
89 3 8 -> 35 8
100 12 7 -> 13 8