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

An idea for a king-of-the-hill challenge:

You have a "memory arena" with a fixed size. You have several programs which "reside" in the memory arena (I mean you take the assembly and put it in the arena). The goal of the game is to get another program to access memory outside of this "arena" which then causes it to die because access outside of the memory arena is not defined. The last program standing wins.

You enter in assembly code (I have not determined which architecture yet). At the beginning of a round all of the entries get randomly placed in the memory arena. Each program will execute one instruction per turn.

It would be very similar to red code but in actual assembler.

Please feel free to post comments

Answer 2

Collatz or Hailstone sequence efficiently

fastest-code sequence number-theory

Sorry for everywhere I posted in the wrong place and thank you to all of the mods for helping me find the sandbox.

---

Winner is the shortest run time to check whether all numbers up to N will end in x=1 or goes 70 iterations without returning to the original number or without decreasing under a step over Log(N) steps in a row under iterating f(x)=x/2 if x is even and f(x)=(3x+1)/2 if x is odd.

Hint: all one needs to show is that for all x under iteration it hits another y in the sequence that has already been shown to hit 1.

---

Sandbox questions

• How can I phrase the above challenge. I set it with parameters that halt for all natural numbers n. I care more about the speed of the program then the shortness of the program.

Answer 3

Kill the mosketeers

Taken a NxN square field, where you are supposed to be on the extreme upper right corner, n mosketeers are waiting an execution instruction that begins with the first lefttmost shooter alternatively until the last righttmost one, in a continuous unceasable order, meanwhile, between any shot and another you are allowed to move one step either to 4 allowed perpendicular directions.

T a period permitted to reload the riffle from a shot to another, dependently of steps taken from a move to another, a step is expressed in other words, as the time taken from two consecutive shots that of a mosketeer and his neighbor, so once T steps are elapsed, the mosketeer takes turn to shot again where two shots can occur in real-time.

Your task, is more than saving your head on your shoulders, but it is rather the ability of killing all the mosketeers while they are reloading their riffles by a knife, noted that : a mosketeer can shot in an horizontal dimention if his turn comes out, and no moketeer is between him and you, morover, a mosketeer do never move.

Given two inputs, N T, say in term of integer output how many mosketeers you are able to kill, return -1 or nil the case you end up killed no matter what you tried.

Example:

input:

   4,3

steps:

...*  |... .|.. ..|. |..| .|.. ..|. |..| .|.. ..|. ...| .... ....
....  |..* .|.. ..|. |..| .|.. ..|. |..| .|.. ..|. ...| .... ....
....  |... .|.* ..|* |.*| .|*. .*|. |*.| *|.. ..|. ...| .... ....
$$$$  |$$$ $|$$ $$|$ |$$| $|$$ $$|$ |$$| $|$$ *$$$ .*$| ..*$ ...*

Output:

  4

---

example 2

input:

   4,2

steps:

...*  |... .|.. |.|. .|.| |... .|.| |... .|.| .... .|.| 
....  |..* .|.. |.|. .|.| |... .|.| |... .|.| .... .|.| 
....  |... .|.* |.|* .|*| |... .|*| |*.. *|.| .... *|.| 
$$$$  |$$$ $|$$ |$|$ $|$| |$*$ $$.$ $$.$ $$.$ *$.$ .$.$ 

Output:

  2

---

Answer 4

Scry sort

In Magic the Gathering, your library is a stack of cards, the effect Scry 2 causes you to take the top two cards of your library and arrange them as you choose on the top and/or bottom of your library.

You have six total choices:

• Put both cards on top in either order
• Put one cards on the bottom and one on top
• Put both cards on the bottom in either order

If you are able to Scry 2 at will, you can repeatedly do so to arrange your library in any order. In this challenge, the cards of your library will be numbered from 1 to n, and your goal will be to arrange them in sorted order.

---

What should be the challenge here?

• Code golf to find the minimum number of Scry 2's needed
• Code golf to find any sequence that arranges your library, no matter how long
• Fastest code or code challenge to sort in as few Scry 2's as possible.

Answer 5

International Choice of Urinal Protocol efficiency

code-golf

A long while ago, Randall Munroe of xkcd fame wrote a blog post entitled Urinal protocol vulnerability. The titular "International Choice of Urinal Protocol" is that when men enter a bathroom that has a row of urinals along the wall, they will first take the end urinals, and then take the urinals that are furthest from the other men. All men seek to avoid awkwardness, which happens when two men use adjacent urinals.

For example, if there are five urinals in a row, then by following this protocol, men will take urinals in this order:

UUUUU
1 3 2

In this case, the packing efficiency is optimal. However, when there are seven urinals, then this happens:

UUUUUUU
1  3  2

This is essentially the worst case. Fewer than half of the urinals are used, and Randall continues investigating when the best and worst cases happen. For this challenge, though, your only task is to calculate the packing efficiency of this protocol when given a number n of urinals, which is k/n where k is the number of urinals taken before awkwardness ensues.

Spec

• Standard I/O and code-golf rules apply.
• Input is a single positive integer n, which may be given as either decimal or unary.
• Output must be either a float or a simplified fraction. If your language cannot do either of these easily (e.g. BF or Retina), then you may simply output k (in decimal or unary).

Test cases

Decimal

 1 1.0
 2 0.5
 3 0.6666666666666666
 4 0.5
 5 0.6
 6 0.5
 7 0.42857142857142855
 8 0.5
 9 0.5555555555555556
10 0.5

Fractions

 1 1/1 {or} 1
 2 1/2
 3 2/3
 4 1/2
 5 3/5
 6 1/2
 7 3/7
 8 1/2
 9 5/9
10 1/2

Urinals taken k

 1 1
 2 1
 3 2
 4 2
 5 3
 6 3
 7 3
 8 4
 9 5
10 5

Note: this is A166079.

Related: The Urinal Protocol, which asks for all the possible ways men could take urinals with no restriction on the first and no awkwardness.

Answer 6

Matching a string using a huge number of steps

regular-expression code-challenge

Your task is to write a regex that matches a string you defined in as close to n steps as is humanly possible.

The regex must match the whole string without the global flag on.

Scoring

The score would be regex length + string length + absolute difference between the number of steps and n.

For example, if n = 65536, this example has 6 bytes as regex, 49152 bytes in the string, and 65539 steps, which would account for a total score of 6+49152+3=49161.

Lowest score wins.

Requirements

1. n = 65536 (2**16)
2. n = 59049 (3**10)
3. n = 40320 (8!)

The total score will calculated from the scores of the three programs.

Questions:

• How can I make this challenge better?

Answer 7

Find the smallest number bigger than the input whose digital sum is the input

code-golf arithmetic

"Digital sum" refers to the sum of all the digits in a number.

For example, the digital sum of 1324 is 10, because 1+3+2+4 = 10.

The challenge is to write a program/function to calculate the smallest number bigger than the input whose digital sum is the input.

Example with walkthrough

As an example, take the number 9 as the input:

9 = 1+8 -> 18
9 = 2+7 -> 27
9 = 3+6 -> 36
...
9 = 8+1 -> 81
9 = 9+0 -> 90

The valid output would be the smallest number above, which is 18.

Specs

Note that 9 is not the valid output for this example, because the reversed number must be greater than the original number.

Note that the input will be positive.

Test-Cases:

 2 => 11
 8 => 17
12 => 39
16 => 79
24 => 699
32 => 5999

References:

This is OEIS A161561.

Answer 8

Light the Way!

This is based on the Lights Out game. There is a grid of tiles, and clicking on a tile (performing a "move") toggles the state of the clicked tile as well as the (orthogonally) adjacent tiles. This variation will also toggle the diagonally adjacent tiles.

It is helpful to note that (on a board with only two states) all moves commute, so the order in which they are performed is not important. It follows that performing a collection of moves a second time will undo what was done the first time.

There are a few ways to present this challenge, so I'll describe some possibilities. Let me know what you think. The challenge could be one of the below:

• Given a board size n (optional) and the initial state of the n-by-n board, determine an optimal collection of moves that will toggle every lit ("on") tile into its dark ("off") state.
• Given n and a sequence of moves performed on an initially dark board of size n, provide the resulting matrix of states.
• A variation on the above involving graphical output.

Input format would be flexible. n >= 1.

---

Snippet to show how the game works:

The board size may be adjusted in the first input field. The second field (functionality added by Conor O'Brien) will take a list of coordinates ([[0,0],[1,2],[3,0],...]) and perform the moves for you.

var table;
var color1 = "aqua",
	color2 = "yellow";
var moveList = [];

window.onload = function () {
	table = document.getElementById("lightGame");
	buildTable();

	var updateButton = document.getElementById("updateButton");
	if (updateButton) {
		updateButton.onclick = buildTable;
	}

	// added by Conor O'Brien
	document.getElementById("perform").addEventListener("click", function() {
		var toPerf = JSON.parse(document.getElementById("moves").value);
		//console.log(toPerf);
		function rec(arr) {
			var m = arr.shift();
			var x = m[0],
				y = m[1];
			var cell = table.rows[y].cells[x];
			update(cell);
			if (arr.length) {
				setTimeout(rec, 500, arr);
			}
		}
		rec(toPerf);
	});
};

function buildTable() {
	// get size
	var input = document.getElementById("size");
	var size = new Number(input && input.value || 5);
	
	var rows = size,
		cols = size;
	
	// clear moves
	moveList = [];
	moveHolder.innerHTML = "[]";
	
	// remove existing rows
	while (table.lastChild) {
		table.removeChild(table.lastChild);
	}
	
	// create new rows
	for (var y = 0; y < rows; y++) {
		var row = document.createElement("tr");
		
		for (var x = 0; x < cols; x++) {
			var cell = document.createElement("td");
			cell.style.backgroundColor = color1;
			cell.x = x;
			cell.y = y;
			cell.onclick = function () {
				update(this);
			};
			row.appendChild(cell);
		}
		table.appendChild(row);
	}
}

function update(cell) {
	var x = cell.x;
	var y = cell.y;
	
	var xMax = table.rows[0].cells.length;
	var yMax = table.rows.length;
	
	// update cell
	changeColor(cell);
	
	// update orthogonally adjacent
	if (x > 0) changeColor(table.rows[y].cells[x - 1]);
	if (x + 1 < xMax) changeColor(table.rows[y].cells[x + 1]);
	if (y > 0) changeColor(table.rows[y - 1].cells[x]);
	if (y + 1 < yMax) changeColor(table.rows[y + 1].cells[x]);
	
	// update diagonally adjacent
	if (x > 0 && y > 0) changeColor(table.rows[y - 1].cells[x - 1]);
	if (x > 0 && y + 1 < yMax) changeColor(table.rows[y + 1].cells[x - 1]);
	if (x + 1 < xMax && y > 0) changeColor(table.rows[y - 1].cells[x + 1]);
	if (x + 1 < xMax && y + 1 < yMax) changeColor(table.rows[y + 1].cells[x + 1]);
	
	// update moves
	// added by Conor O'Brien
    moveList.push([x, y]);
    moveHolder.innerHTML = JSON.stringify(moveList);
}

function changeColor(cell) {
	cell.style.backgroundColor = cell.style.backgroundColor === color1 ? color2 : color1;
}

function getStyle(elt, styleProp) {
	if (elt.currentStyle)
		return elt.currentStyle[styleProp];
	return document.defaultView.getComputedStyle(elt, null)[styleProp];
}

body {
	background-color: darkslategray;
	color: white;
}
#gameDiv {
	text-align: center;
}
header {
	margin: 25px;
}
h2, h4 {
	color: red;
	text-shadow: -2px -2px black;
}

#lightGame {
	border: 1px solid white;
	margin: auto;
}
#lightGame td {
	/*background-color: aqua;*/
	padding: 1px;
	height: 25px;
	width: 25px;
}
#updateDiv {
	margin: 25px;
}
button {
	margin-left: 10px;
}

#autoMoveDiv {
	margin-top: 10px;
}

footer {
	position: fixed;
	bottom: 0px;
	width: 100%;
}
footer small {
	color: cyan;
	position: absolute;
	bottom: 0px;
}
img {
	float: right;
}

<div id="gameDiv">
	<header>
		<h2>Light Game</h2>
	</header>
	<div>
		<table id="lightGame">
		</table>
	</div>
	<div id="updateDiv">
		<input id="size" name="size" type="number" min="1" max="20" pattern="\d{1,2}" value="5" required />
		<button id="updateButton" type="button">Update</button>
	</div>
	<div>
		Your moves: <span id="moveHolder">[]</span>
	</div>
	<div id="autoMoveDiv">
		Auto move: 
		<input id="moves" />
		<button id="perform" type="button">Do Moves</button>
	</div>
</div>

---

Related Questions

JsFiddle of the snippet I made.

Answer 9

Version Comparator

Given two version strings, return a positive, negative or zero value depending on which one is earlier. Version strings consist of one or more non-negative integers separated by full stops, optionally suffixed by a lowercase letter and a final non-negative integer. Examples of versions:

1.5a2
1.5b1
1.5
2.19
2.20b
2.20 or 2.20.0 (these should compare equal)
8.1a
8.1
9
10

When comparing versions the integers should of course be compared numerically, not lexically. Missing components should compare as zero against numbers, but they compare after letters. You should then be able to recognise that the above versions are in version order, but you can choose whether this should be a positive or negative result. Reversing the parameters should obviously negate the sign of the result, but you can return a different absolute value if you prefer.

Builtins that compare versions are disallowed, but things like regexes are OK.

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

Answer 10

Find the duration of a worst-case brute-force attack

Given the following information about a 7-bit ASCII-encoded password and the computer that will crack it with a brute-force attack:

• Length of the password in characters
• Charset size (i.e total count of the possible characters one character in the password can be)
• Number of passwords the computer can test in one second millisecond (rounded down)

Write the shortest program that finds out how long the attack will take in the worst-case scenario where the computer tries all possible passwords.

• The output is the duration in this format: years months days hours minutes seconds milliseconds
  • One "month" is 30 days long.
  • Fractions of milliseconds are rounded up.
  • You can assume that the cracking finishes immediately if it takes less than 50 milliseconds, and make the program print out Instant in such cases.
  • Similarly, the cracking can be considered Neverending if it takes more than 292 billion years.
• The program can output using any method, from merely printing to STDOUT to causing a kernel panic/bluescreen with the duration as the error message.
• The input method to get the info about the password/the machine can be anything, as well. Don't use standard loopholes though.
• It's not enforced, but strongly encouraged to write a standalone program.

Here's how to calculate the charset size:

• Start with 0.
• If there's a digit (in the password), add 10.
• If there's a lowercase letter, add 26.
• If there's an uppercase letter, add another 26.
• If there's punctuation, add 32 (7-bit ASCII has this many punctuation characters).
• If there's a whitespace character, add 2. Whitespace characters are horizontal tab (0x09) and space (0x20).
• Any other character counts as non-printable (including backspace (0x08), DEL (0x7F), line feed (0x0A) and carriage return (0x0D)). Add 29 if there's any of them.

Count of all possible passwords is (charset size)^{password length}.

Here are some applicable-in-real-life cases you can test your program with (let's assume the computer that will crack them can test 1 billion passwords per second, which equals to 1,000,000 passwords/millisecond):

• 4 characters, charset size 10 (PIN) - 10,000 passwords, output is 0 0 0 0 0 0 1 or Instant
• 8 characters, charset size 94 (at least one uppercase letter, one lowercase letter, one digit and one punctuation) - 6,095,689,385,410,816 passwords, output is 0 2 10 13 14 49 386
• 10 characters, charset size 2 (weakest valid Discourse password, contains whitespace only) - 1024 passwords, output is 0 0 0 0 0 0 1 or Instant
• 25 characters, charset size 26 (correcthorsebatterystaple) - 236,773,830,007,967,588,876,795,164,938,469,376 passwords, output is 7612327353651221350 2 14 0 26 4 939 or Neverending
• 127 characters, charset size 96 (strongest password on newer Windows releases) - written below
• 1024 characters, charset size 36 (4096-bit PGP key represented as a hexadecimal number) - written below

These are the stats of the maximum-strength Windows password:

Passwords: 560,333,510,486,846,899,384,847,242,571,130,277,659,458,884,466,874,695,582,912,274,460,529,559,443,783,341,570,989,525,270,653,136,186,432,110,439,597,936,820,880,106,519,625,601,191,574,799,863,912,148,304,962,133,852,037,202,160,056,511,510,962,873,278,300,126,526,144,267,006,137,180,032,492,751,016,171,207,701,495,935,943,049,216
Output: 18014837657113133339276210216407223432981574217685014647084370963880194169360318337544673523362047845500003550655797865897637169483847774934889398916928636347805229296463546812516445182705545212838429981490065783731353925307067135133992 5 15 19 58 55 944
Alternate output: Neverending

And these are the stats of the PGP key:

Passwords: 4,505,684,579,918,576,285,346,738,866,335,056,898,110,301,685,668,199,078,230,938,179,212,682,315,156,231,410,185,391,761,603,272,976,014,035,539,665,517,248,679,228,261,440,294,129,198,036,262,705,242,310,399,830,546,082,361,923,420,737,260,766,677,891,361,176,003,624,143,368,380,527,062,643,297,677,246,518,686,688,642,023,537,863,317,793,178,302,508,440,097,154,593,959,832,175,055,427,351,149,410,096,495,695,380,712,810,868,774,475,142,767,054,868,274,802,269,522,299,482,066,464,842,097,715,922,988,138,315,118,067,288,670,934,735,264,524,936,706,249,961,394,413,647,964,221,767,703,673,264,468,419,121,528,644,906,680,808,060,759,817,669,970,046,776,525,266,199,099,671,937,918,801,013,826,958,891,378,841,908,663,991,372,649,027,188,879,525,186,690,599,345,723,173,064,252,017,258,129,131,786,488,462,307,158,861,824,049,980,863,991,149,295,162,169,512,952,373,415,599,734,988,691,348,925,488,351,712,593,858,837,027,205,238,618,188,975,201,320,681,214,515,875,812,195,250,605,867,622,987,451,763,883,339,709,733,502,125,838,221,788,546,339,051,347,360,900,518,381,976,167,289,930,943,228,024,924,785,158,428,496,314,937,921,503,359,298,542,415,845,218,449,360,806,235,379,253,546,728,753,218,950,843,742,471,105,739,555,344,908,900,309,982,913,223,331,321,839,212,821,903,239,320,600,564,890,951,140,667,647,680,682,245,252,370,183,758,578,065,733,075,207,856,432,661,797,090,351,101,165,469,273,829,754,476,555,209,675,613,232,875,323,406,611,257,057,059,099,019,633,298,079,410,970,345,108,939,943,042,100,267,260,413,671,556,828,411,902,575,269,208,445,279,433,655,878,082,023,068,697,154,581,711,817,787,688,949,105,583,339,471,599,190,831,084,304,744,483,799,555,478,063,729,574,297,623,870,804,763,558,027,580,772,927,971,329,879,231,979,556,301,616,929,595,576,646,883,067,201,999,872,899,862,889,211,861,332,535,050,455,387,251,034,043,732,447,006,164,551,883,918,733,705,027,099,846,583,024,013,092,062,384,703,436,459,115,108,358,829,136,251,317,699,709,899,140,949,893,425,335,769,021,022,912,434,045,643,544,474,460,899,799,213,759,568,795,794,758,914,390,056,283,305,470,380,859,003,818,724,678,434,816
Output: 144858686339974803412639495445442930108998896787172038266169565946909796654971431654622934722327449074525319562291578211137739886840732034401886018044055761311424449664413690224320369299057721231224396352345948448015131278860508182828147139982752631922511354755096078964028889980704480936709984283352948061204198196785328857204061945957268141550998891534834171375541476907019128991072373909056348731183618329634024763694746476776233417623704464804027405450152026906721990999895827471385353870130056140660354679074035526421905828555132520211676677361401337091034117370453939870215183392876069255694823382473711006907851853458746913295694931911314073828877816349504523255816791677974298928074750103049081088894521647398444396729546431174466495229648516324713327536964168664025148591452750098101445502202880078966283755495859954505040675103796820824907455740718188735077328268047865426806174561044520100917915500979652319301547868727504821981520811835192875926630119576922600465887060849654310721522802609638109522185755307201898676461606130734024600227278608209698963323356340446015796148617903068964091403666193996894642822309315198786075754477250953946657292049336910661279747924178751224344877465829301109562043071275369906871767991229129085786546569052197642684662087651029574035646976531236521763373563846425925268656816387911380422031991615290633773786744123323731112880994579065426763237282889858685438654794679302568796507941872848896038602862540480809810919146613018187362072374644736799940064590439265446053422181856817801562474722208358918298576208528044087753034364036 10 24 22 32 4 679
Alternate output: Neverending

code-golfcryptographydate

Answer 11

Array of Integers to Array of Digits

code-golf

Given an array of arbitrary length containing only integers, output an array of integers of each digit of each integer in the array.

Notes

• The input array will only consist of integers in base 10

• The integers will be in the range of [0, MAX_INT] where MAX_INT is the greatest value an integer can have in your language

• Assume that all integers will be positive, however you can interpret the integers as signed or unsigned

• String manipulation and the use of any regex is banned by default

• The outputted array must be exactly 1 deep and contain only integers

• The order of the digits in the outputted array must be exactly as they were in the inputted array

• Leading zeros are to be stripped, as they should be when parsed as an integer

Examples

[2, 3, 5, 7, 11, 13] -> [2, 3, 5, 7, 1, 1, 1, 3]
[1, 2, 3, 4, 5] -> [1, 2, 3, 4, 5]
[123, 456, 789, 101112] -> [1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 0, 1, 1, 1, 2]
[0, 000, 000123] -> [0, 0, 1, 2, 3] //'000' is treated as '0' and '000123' is treated as '123'

Answer 12

Ping Pong

The Challenge

This challenge is to make a program that prints a text ping-pong animation. Your program is to display a string of tildes with a PING on it moving to the right. Each tick, the text PING moves one to the right one character, reducing the number of tildes on the right by one and increasing the amount on the left by one. Once the PING reaches the right side of the string, it changes to a PONG and the reverse happens (i.e it moves to the left instead).

Rules

• The number of tildes must always be the same
• The number of tildes must be at least 30
• The number of milliseconds between ticks must be at least 10 ms and at most 1 s
• The PING must start at the left hand of the string

Scoring

Your score is the number of bytes plus/minus the following (all that apply):

• -10 bytes for browser implementation using the ping after the hash
• +10 bytes if your implementation does not clear previously outputted frames
• More suggestions welcome

Lowest score wins.

Example Implementation (JS, Ungolfed)

i=0;b=false;len=50;td=40;function urlPong(){location.hash=new Array(i+1).join("~")+(!b?"PING":"PONG")+new Array(len-4-i+1).join("~");if(!b){if(len-4-i<=0){b=true;}else{i++;}}else{if(i<=0){b=false;}else{i--;};}setTimeout(urlPong,td);}urlPong();

Answer 13

Implement this cipher

(I'm not sure what to call this cipher)

Goal

Use the algorithm (explained in the Algorithm section) to implement a certain cipher.

The program must read input from STDIN or the closest available equivalent, use the algorithm to generate the ciphertext and a key.

The ciphertext and the key will be written to STDOUT or the closest available equivalent, preferably with the format (ciphertext)\n(key).

Algorithm

Convert the characters in the string into the respective ASCII values. For example:

Hello -> 72 101 108 108 111

Next, you will need to generate a key as long as the string with random numbers in the range of 0-9.

Hello -> 62841

Add the integers in the random number sequence to the ASCII values of the string. In the above examples, 72 would become 78, and 101 would become 104.

72 + 6 = 78, 101 + 2 = 104, 108 + 8 = 116, etc

Next, convert the new ASCII values back to characters. In the above examples, the text Hello has become Nhttp.

Examples

(These are simply examples of what the output might look like. The output can and will vary.)

Hello, World!

Hgqqu/$\\p{ni$
0255634519253

---

This will be encoded
    
Zhjs$~koo gj$iuhofgj
60104723305544750226

Rules

• Submissions must be full programs.
• Languages newer than the challenge are allowed.
• Submissions will be scored in bytes.
• Standard loopholes are forbidden.
• This is code-golf, so the shortest code wins.

---

I'm sure this challenge needs a little tidying up and making it look and sound a bit nicer. I'm not very good at writing challenges, so I'd like some advice.

Answer 14

Latin vs Greek vs Cyrillic / Battle of the Alphabets

code-challengeimage-processingclassificationpattern-recognition

---

Meta: This is just a rough draft, the challenge is still under development, feel free to add suggestions as comments or via chat pinging @flawr

Points that are unclear so far:

• Is there one fixed typeface for all three?
• Will the image always be provided in the exact horizontal orientation?
• How long will the provided text be, just single words? A single line? A multiline piece of text?

---

These three alphabets are relatively similar and even have some letters in common, but also a lot of distinct letters. In this challenge, you have to write a classifier that can distinguish these three alphabets, when presented with a raster image of a corresponding text.

This is an image from Wikipedia that shows the differences in the capital letters:

This challenge was inspired by this message.

Answer 15

Don't let those functions get away

code-golf string

Introduction

My imaginary language, PremOpt discourages the use of functions. They are the source of every performance problem. Your task today is to fix beginner PremOpt programmer's code.

Every statement's and loop's (if, switch, while, for) content is enclosed in brackets:

<if/switch/while/for> <statement here> {
    <stuff>
}

Switch cases are one liners:

switch <value> {
    case <val1>: <statement1>;
    case <val2>: <statement2>;
    case <val2>: <statement2>;
}

Functions look like these:

function <name>(arg1, arg2, arg3) {
    // Stuff here
}

// Calling a function:
<name>(arg1, arg2, arg3);

Other lines end with a semi-colon.

Variables don't need to be declared, they're already initialized to null, you can set a variable to a value with

variableName = value;

Outputting a value is done by doing

out-><value>

Input

Your input is a string with a piece of code. Each row is separated with a line-feed. The input may or may not contain functions.

Output

You need to remove the functions from the code, and put their content to the where they were called.

Examples:

function hello() {
    sayHello1();
    sayHello2();
}
hello();

becomes

sayHello1();
sayHello2();

Multiple function calls:

function func() {
    doStuff1();
    doStuff2();
}
func();
func();

becomes

doStuff1();
doStuff2();
doStuff1();
doStuff2();

If the function takes in arguments:

function argFunc(arg1, arg2) {
    doStuffWithArg(arg1);
    doStuffWithArg2(arg2);
}
argFunc(myVar1, myVar2);
argFunc(myVar3, myVar4);

then you need to change the arguments inside the function to match with the calling arguments

doStuffWithArg(myVar1);
doStuffWithArg2(myVar2);
doStuffWithArg(myVar3);
doStuffWithArg2(myVar4);

Test cases

fibonacci sequence:

a = 1;
b = 1;
function getNextNumber(num1, num2) {
    return num1 + num2;
}

while(true) {
    a = getNextNumber(a, b);
    out->a;
    b = getNextNumber(a, b);
    out->b;
}

Should become

a = 1;
b = 1;

while(true) {
    a = a + b;
    out->a;
    b = a + b;
    out->b;
}

FizzBuzz:

for (counter = 0; counter <= 100; counter++) {
    checkNumber(counter);
}

function checkNumber(num) {
    if (num % 3 == 0  num % 5 == 0) {
        out->"Fizz Buzz";
    } else if (num % 3 == 0) {
        out->"Fizz"
    } else if (num % 5 == 0) {
        out->"Buzz"
    } else {
        out->num;
    }
    out->newLine;
}

Becomes:

for (counter = 0; counter <= 100; counter++) {
    if (counter % 3 == 0  counter % 5 == 0) {
        out->"Fizz Buzz";
    } else if (counter % 3 == 0) {
        out->"Fizz"
    } else if (counter % 5 == 0) {
        out->"Buzz"
    } else {
        out->counter;
    }
    out->newLine;
}

Rules

• There'll be no recursive functions in the input
• Standard loopholes are forbidden

Answer 16

fix show

Your task is given n, you must print first n character returned from Haskell expression fix show.

Let me explain how fix show produces the "magic" string.

show is just escaping the string and then add quote. Since the resulting string consists only double quotes and backslash, show then essentially just put backslash before every character then quote the resulting string.

show str = '"' : concat ( zipWith (\x y->[x,y]) (repeat '\\') str ) ++ "\"" -- Well, this is not what prelude give, but

fix is, well, fixpoint combinator. But thanks for laziness, it won't do a infinite loop first.

The string is equivalent to the string defined below:

Assuming there is a series of string. The first string is "" and the next series is just application of show to previous string:

"" "\"\"" "\"\\"\\"\"" "\"\\"\\\\"\\\\"\\"\"" "\"\\"\\\\"\\\\\\\\"\\\\\\\\"\\\\"\\"\""

For all n, there is k so that for all l above k, n-th character of l-th string from series is same. That character is the n-th character of fix show

TODO: I hate the sentence above, please fix it.

The first 100 character in resulting string

"\"\\\"\\\\\\\"\\\\\\\\\\\\\\\"\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

So, another implementation is

fixshow = '"' : zip (repeat '\') fixshow ++ "\""

Rules

1. You are not allowed to use function fix, show, and the equivalent functions.
2. Shortest answer wins.

Sandbox question

Is there another way to prevent answer like flip take$fix show, or without importing f k=k$f k;j n=take n$f show. And how about array programming language like APL, J and Jelly?

Answer 17

Golfing with ultrasound

Within medical physics, the percentage of ultrasound reflected between material boundaries can be calculated using two pieces of data: the density(p) and the speed(c) at which sound travels through the material.

To calculated the percentage reflection the following equation can be used

(Z1-Z2)^2 / (Z1+Z2)^2

Where Z1 and Z2 are the acoustic impedances(Z) of the two materials. Z is calculated such that Z=pc That is density * speed of sound in the material

This is where the issue lies

I have two ways of asking the question

1:

Given the acoustic impedance for two materials, calculate the percentage reflection.

2:

Given the density and speed of sound in two materials, calculate the percentage reflection

Reason

The first method will be much simpler, in the way you are just plugging values into a formula. However I feel that method 2 is heavy on the inputs, and I understand that four inputs is a large number of inputs in golfing challenges

On posting the question I will also add a number of test cases

Answer 18

Write a BF to Hexagony Converter!

---

code-golfbrainfuckcode-generationhexagonal-grid

---

According to community moderator Martin Ender ♦:

Hexagony is Turing-complete as any brainfuck program can be translated to Hexagony with some effort. (Source)

Your program's job is simple: take a valid brainfuck program, and convert it to an equivalent Hexagony program. For completeness, here are all the relavant commands in both BrainFuck and Hexaongy (taken from esolangs.org).

brainfuck

brainfuck operates on an array of memory cells, also referred to as the tape, each initially set to zero. There is a pointer, initially pointing to the first memory cell. The commands are:

• > Move the pointer to the right
• < Move the pointer to the left
• + Increment the memory cell under the pointer
• - Decrement the memory cell under the pointer
• . Output the character signified by the cell at the pointer
• , Input a character and store it in the cell at the pointer (-1 for EOF)
• [ Jump past the matching ] if the cell under the pointer is less than or equal to 0
• ] Jump back to the matching [ if the cell under the pointer is nonzero

All characters other than ><+-.,[] should be considered comments and ignored.

Modifications:

• Infinite tape in both directions
• Arbitrary precision integers (like hexagony)
  • No overflow/underflow
• [ acts the same for negative numbers as it does for 0

Hexagony

Source code

The source code consists of printable ASCII characters and line feeds and is interpreted as a pointy-topped hexagonal grid, where each cell holds a single-character command.

Because of this restriction, the number of commands in the source code will always be a centered hexagonal number. For reference, the first 10 centered hexagonal numbers are:

1, 7, 19, 37, 61, 91, 127, 169, 217, 271

When reading a source file, Hexagony first strips all whitespace characters. Then the remaining source code is padded to the next centered hexagonal number with no-ops and rearranged it into a regular hexagon. This means that the spaces in the examples above were only inserted for cosmetic reasons but don't have to be included in the source code. The following three programs are identical:

   a b c  
  d e f g 
 h . . . .  
  . . . .   
   . . . 

abcdefgh...........

abcdefgh

But note that

abcdefg

would instead be the short form of

   a b 
  c d e  
   f g

Control flow

Hexagony has 6 instruction pointers (IPs). They start out in the corners of the source code, pointing along the edge in the clockwise direction. Only one IP is active at any given time, initially the one in the top left corner (moving to the right). There are commands which let you switch to another IP, in which case the current IP will make another move (but not execute the next command), and then the new IP will start by executing its current command before making its first move. Each IP has an index from 0 to 5:

   0 . 1
  . . . .
 5 . . . 2
  . . . .
   4 . 3

The direction of an IP can be changed via several commands which resemble mirrors and branches.

The edges of the hexagon wrap around to the opposite edge. In all of the following grids, if an IP starts out on the a moving towards the b, the letters will be executed in order before returning to a:

   . . . .          . a . .          . . k .          . g . .   
  a b c d e        . . b . .        . . j . .        . h . . a  
 . . . . . .      g . . c . .      . . i . . e      . i . . b . 
. . . . . . .    . h . . d . .    . . h . . d .    . j . . c . .
 f g h i j k      . i . . e .      . g . . c .      k . . d . . 
  . . . . .        . j . . f        f . . b .        . . e . .  
   . . . .          . k . .          . . a .          . f . .   

If the IP leaves the grid through corner in the direction of the corner there are two possibilities:

-> . . . .   
  . . . . .  
 . . . . . . 
. . . . . . . ->
 . . . . . . 
  . . . . .  
-> . . . .  

If the current memory cell (see below) is positive, the IP will continue on the bottom row. If it's zero or negative, the IP will continue on the top row. For the other 5 corners, just rotate the picture. Note that if the IP leaves the grid in a corner but doesn't point at a corner, the wrapping happens normally. This means that there are two paths that lead to each corner:

      . . . . ->   
     . . . . .  
    . . . . . . 
-> . . . . . . .
    . . . . . . 
     . . . . .  
      . . . . ->

Special characters

. is a no-op: the IP will simply pass through.
@ terminates the program.

Arithmetic

) increments the current memory edge.
( decrements the current memory edge.

I/O

, reads a single byte from STDIN and sets the current memory edge to its value, or -1 if EOF is reached.
; takes the current memory edge modulo 256 (positive) and writes the corresponding byte to STDOUT.

Control flow

$ is a jump. When executed, the IP completely ignores the next command in its current direction. This is like Befunge's #.
_, |, /, \ are mirrors. They reflect the IP in the direction you'd expect. For completeness, the following table shows how they deflect an incoming IP. The top row corresponds to the current direction of the IP, the left column to the mirror, and the table cell shows the outgoing direction of the IP:

  cmd │  E SE SW  W NW NE
──────┼────────────────────
   /  │ NW  W SW SE  E NE
   \  │ SW SE  E NE NW  W
   _  │  E NE NW  W SW SE
   |  │  W SW SE  E NE NW

< and > act as either mirrors or branches, depending on the incoming direction. The cells indicated as ?? are where they act as branches. In these cases, if the current memory edge is positive, the IP takes a 60° right turn (e.g. < turns E into SE). If the current memory edge is zero or negative, the IP takes a 60° left turn (e.g. < turns E into NE).

  cmd │  E SE SW  W NW NE
──────┼────────────────────
   <  │ ?? NW  W  E  W SW 
   >  │  W  E NE ?? SE  E

[ switches to the previous IP (wrapping around from 0 to 5).
] switches to the next IP (wrapping around from 5 to 0).
# takes the current memory edge modulo 6 and switches to the IP with that index.

Memory manipulation

{ moves the MP to the left neighbour.
} moves the MP to the right neighbour.
" moves the MP backwards and to the left. This is equivalent to =}=.
' moves the MP backwards and to the right. This is equivalent to ={=.
= reverses the direction of the MP. (This doesn't affect the current memory edge, but changes which edges are considered the left and right neighbour.)

Some commands/description omitted for conciseness, full list here.

Other rules:

• Input/Output may be done however is most natural for your language
  • Output does not have to be formatted like a hexagon
• Must run in a reasonable amount of time
  • Minimal brute-force
  • No brute-forcing the entire program
• You can only use Hexagony commands specified in this challenge.
• This is code-golf, so shortest code wins
  • {META NOTE: I know this challenge is hard, is there a better way to score?}
• As usual, standard loopholes are prohibited.

Test Cases:

Input: (cat)

,.[,.]

Output: (example)

   \ . .
  < _ . .
 . _ ; . .
  . . > ,
   . @ .

Input: ("123")

+++++++++++++++++++++++++++++++++++++++++++++++++.+.+.

Output: (example)

     ) ) ) ) )
    ) ) ; ) ; /
   ) ) ) ) ) ) /
  ) ) ) ) ) ) ) /
 ) ) ) ) ) ) ) ) /
  ) ) ) ) ) ) ) )
   ) ) ) ) ) ) )
    ) ) ) ) ) )
     . . @ ; <

Input: (@primo's infinite Fibonacci)

+[[<+>->+>+<<]>]

Output: (example)

       ) \ . . . . |
      . | . / { } < .
     . . . . > [ . / >
    . . . . . . . . . .
   . . . . . . @ . . . .
  / . ] < . > < . ] . . .
 _ > " ' / | . > < . . . .
  _ / . . . / . . [ . . .
   . / . . . . . . ) . .
    . . . . . . . . ] .
     . . . [ . . . . |
      . . [ . . . . (
       . \ ) ] ) ] <

Answer 19

Platformer game

code-golf game

Write a platformer game.

Rules:

• Keyboard input, minimum three commands: left, right and jump;
• Real-time. Screen should update (and the game iterate) on timer. Update speed should not depend on CPU speed. FPS should be between 2 and 120;
• It should be possible both to win and to lose (the game can although be very hard and require preparing a special bot to win or to lose);
• Playing field should have at lest 64 positions, minimum width is 6, minimum height is 5.
• Player may move left, right or jump. Player moves down automatically unless on a platform. Jumping means moving up for some limited time (not higher than 67% of playing field's height), then falling down like usual.
• Falling down outside playing field is losing the game. Stepping on 6 distinct platforms is a win.

• Player, platforms and borders of area should be visible on playing field. If output method is ASCII art, it may looks like this:

  .....----...
  ............
  [email protected]
  ..---.......
  .......---..
  ............
  

• Platforms may be horizontal, vertical, diagonal. Platforms should not overlap (except of differently oriented). Platform's projection to horizontal and vertical axes should not overlap for at least 4 platforms. Example of too projection-overlapping playing field:

  ............
  ....@.......
  .--.--..--..
  ............
  .--.--..--..
  ............
  

• Platforms may move. Overlapping rules apply only to initial positions.

• The game should track losing and winning conditions and stop the game, outputting distinct messages in case of lose or win.

Answer 20

Compute h-index of PPCG users

code-golf stack-exchange-api internet number

Thanks to @Suever for his help refining this challenge.

Background

The h-index is a commonly used metric that measures the amount and quality of publications of a given scholar or researcher. It is defined as follows:

A scholar with an h-index of n has published n papers each of which has been cited at least n times.

Adaptation for PPCG

In this challenge I propose to compute the h-index of PPCG users based on the analogy

• paper → answer;
• paper's citations → answer's vote count, defined as upvotes minus downvotes.

The following examples illustrate the computation of h-index. The array to the left is the vote count of answers in descending order for a hypothetical user, and the number to the right is the resulting h-index:

[5 3 2 1 1]    2
[1 1 1]        1
[]             0
[-1 -2]        0
[0]            0
[9 4 3 ...]    3

Referring to the last example, note that we don't need to know the array entries after the 3.

The challenge

Given a user identification, output their h-index.

Rules

User identification can be defined as anything reasonable, such as user number, user name, or user name without spaces.

The result must be based on actual data from the PPCG site. You may want to take a look at the StackExchange API, for example here.

Note that some users have a lot of answers. For one such user the API may not give all the results, or may only give them split across several chunks. However, if you ask the API to provide the results with an appropriate sorting you may not need all of them to compute the h-index (see last example above). Also, you may assume that the h-index of any user will be less than 100.

If the answer can't be tested in an online compiler (for example due to restrictions to read web content), you are encouraged (although not required) to post some evidence that the answer works, such as a screen capture.

This is code golf. Fewest bytes wins.

Table of h-indices

After submitting your answer, you may optionally edit the table below to include your own h-index, in the indicated format. Please keep the table in decreasing order, so that users with higher h-indices appear higher on the table. I will remove the dummy user names when the table has some actual content.

Example user name: 5
Another example: 3
Yet another user: 3

Answer 21

What is closer?

Tags: math,code-golf

---

Inputs: a, b (Both integer and positive) .Output: Integer, in natural numbers sequence.

We have one single atom which has a electrons, we ionize the atom with b positive charges (take b electrons out).

The output is the sum of the orbital quantum numbers (n,l,ml) which is nearest to the atom shell.

EXAMPLE: We take 3 electrons from ₂₆Fe, Now we have ₂₆Fe³⁺. We need to get the sum of the nearest remained orbitals quantum numbers to the shell.

We have this configuration for Fe³⁺: [Ar], 3d³, 4s²

The nearest orbital to shell has these numbers:

n = 4
l = 0
ml = 0

In this case:

a => 26
b => 3
output => 4

---

My 3rd grade chemistry teacher asked me once to create such a program, but I didn't success, I found the paper that my teacher wrote these descriptions on it and I typed it here because I believe that someone might create an interesting code-golf for this.

Answer 22

king-of-the-hill

KotH Chess Warriors.

This game will be based on fairy chess, but really could be imagined to be anything else.

Submissions will include both: A function that determines the moves of the piece (as in, how the piece can move), called at the start, and a function that determines how it moves each turn, called each turn, of course. Bot's move simultaneously; strategy is needed. A piece may make 5 moves in a row before it must rest.

Bot's will be able to do any valid move they choose, and the input they will get when deciding what to do will be: a value that can be 2, 1, 0, or -1, for each possible move. 2 denotes that an ally is in that square, 1 denotes that an enemy is in that space. 0 denotes an empty space which could be moved to, -1 represents an illegal move, which may result from the board ending or another piece in the way. If a piece attempts to move into it's ally, the following things could happen; A) ally stays still; Piece stays where it is. B) ally moves; Piece moves where it wishes. C) ally is captured; Piece recaptures

See below for early stage point spending system

Sandbox

I don't have the experience to host this challenge, so someone who can program these kind of things will need to help.

I have sketched out some movement point system, but I need to figure out how large the board is, and so how valuable riders (pieces that move continously, like a rook), would be, compared to leapers, before i could finalise it

Here is the quick system done, which could clearly be improved (for one thing, the multiple move thing probably needs to be a bit more expensive):

---

Point buying system

Points: each piece receives (to be decided) points base move: points spent on a move are as so. Largest dimension + floor(small dimension/2). There are no riders in this mode; Only repeated movement Repeated movement by x cost:*ceil(x^1.25) make move-only=/2 It is possible to have a leaping attack and sliding attack on the same square; it is also possible to have only one of these able to attack; How this is sorted is that both moves get their own value, and so you can attack if the attack move by itself can reach there.

Examples for base move costs:

• Any king move: 1
• any knight move: 2
• Zebra move:4
• Camel move:3

PLEASE NOTE: These move values on their own are not representative of how powerful a piece with that move actually is; A knight is better than a camel or zebra. However, when paired with other moves, the zebra and camel moves may become effective.

Example of moves that can be purchased:

     1
7   2  3
6    @55555
     4

• move 1=(2+floor(0/2)):2 points
• move 2=(1+floor(1/2)):1 point
• move 3=(2+floor(1/2)):2 points
• move 4=(1+floor(0/2)): 1 point
• move 5=((1+floor(0/2))*ceil(5^1.25))=8 points
• move 6=(5+floor(0/2))=5 points
• move 7=(5+floor(1/2))=5 points

in total, this piece costs: (2+2+1+1+8+5+5) 24 points.

---

Considerations:

• How large the board is. I'm fairly sure of having a cylindrical board; the left wraps to the right and vice versa.

• how exactly turns work. So far, I have thought that the way it works is this: Everyone moves simultaneously. When you move, you deplete your remaining moves, which tops and starts at 5. You can choose to not move, and replenish your moves at any point.

  However, this could induce stale games which don't end properly.

Answer 23

Calculate my total hours

I record the work I do for one of my customers using a flat file in the following format:

0000-00-00 0000-0000 0.0 code0000 free text

The 0.0 represents the amount of time spent on the task identified by code0000, where 0000 is an optional numeric task ID and code is a project code (and does not contain digits or spaces).

Because I'm lazy, I need as short a program as possible to calculate subtotals of my total time for each project, plus a grand total. If you are using plain text output it should show the hours first and then the project code on the same line, and then the grand total on a line on its own with no code. You don't need to use a specific numeric format but you should be capable of dealing with half hours (0.5) in both the input and output.

Answer 24

Undone Mathematics

Definitions

I define the following:

nᵗʰ Undone Addition of A

Let ⁿ+ᵣ A denotes the nᵗʰ Redacted Addition of A; the sum of the elements of A after n layers have been removed in every dimension:

 ²+ᵣ [1,2,3,4,5,6,7] = ∑ [3,4,5] = 12    // 1D: remove leading and trailing elements

     [[1,1,3]
 ¹+ᵣ  [4,2,5]  = ∑ [2] = 2    // 2D: remove leading and trailing rows and columns
      [3,4,1]]

Then ⁿ+ᵤ A denotes the nᵗʰ Undone Addition of A; the nᵗʰ Redacted Addition of A plus the sum of the elements of A:

 ²+ᵤ [1,2,3,4,5,6,7] = ²+ᵣ [1,2,3,4,5,6,7] + ∑ [1,2,3,4,5,6,7]

     [[1,1,3]        [[1,1,3]      [[1,1,3] 
 ¹+ᵤ  [4,2,5]  = ¹+ᵣ  [4,2,5]  + ∑  [4,2,5]
      [3,4,1]]        [3,4,1]]      [3,4,1]]

nᵗʰ Undone Multiplication of A

Let ⁿ×ᵣ A denotes the nᵗʰ Redacted Multiplication of A; the product of the elements of A after n layers have been removed in every dimension:

 ³×ᵣ [3,2,1,1,2,3,1,1] = ∏ [1,2] = 2    // 1D: remove leading and trailing elements

Then ⁿ+ᵤ A denotes the nᵗʰ Undone Multiplication of A; the nᵗʰ Redacted Multiplication of A times the product of the elements of A:

 ³×ᵤ [3,2,1,1,2,3,1,1] = ³×ᵣ [3,2,1,1,2,3,1,1] × ∏ [3,2,1,1,2,3,1,1]

nᵗʰ Undone Average of A

Let μ denote the average (arithmetic mean), i.e. μA = ^(∑A)⁄_N and ⁿμᵣA denote the nᵗʰ Redacted Average of A; the average of the elements of A after n layers have been removed in every dimension:

 ³μᵣ [3,2,1,1,2,3,1,1] = μ [1,2] = 1.5

Then ⁿμᵤ A denotes the average of the nᵗʰ Redacted Average of A and the average of the elements of A:

                          ³μᵣ [3,2,1,1,2,3,1,1] + μ [3,2,1,1,2,3,1,1]  
 ³μᵤ [3,2,1,1,2,3,1,1] = ─────────────────────────────────────────────
                                               2

Task

With all this in mind, create an interpreter that will evaluate expressions that use the below operations (numbers are just examples). Alternatively, extend the language of your choice to include the notation.

1 + 2        Addition
3 × 4        Multiplication
μ [5,6]      Average
7 +u [8,9]   Undone Addition
9 ×u [1,2]   Undone Multiplication
2 μu [3,4]   Undone Average

Note that you do not need to implement redacted operations. They were only defined above to facilitate the definitions of the undone operations.

You may substitute any ASCII or Unicode symbol for +, ×, and μ as long as you stay consistent: You may not choose * with ×u.

Each undone operator has a higher order precedence than their normal counterpart.

Test cases:

2+u [1,2,3,4,5,6,7] → 40

1+u [[1,1,3][4,2,5][3,4,1]] → 26

3×u [3,2,1,1,2,3,1,1] → 72

3μu [3,2,1,1,2,3,1,1] → 1.625

0.1 × 2+u [1,2,3,4,5,6,7] → 4

2+u [1,2,3,4,5,6,7] × 0.1 → 4

0+u [[[1,1][3,2]][[1,3][3,1]]] → 15

1+u [[[0,1,1][2,1,1][1,0,0]][[2,2,2][2,2,0][1,0,2]][[1,2,0][2,1,1][2,1,2]]] → 34

1×u [[[1,1,2][1,1,1][1,2,1]][[1,2,2][2,2,1][2,2,1]][[1,1,1][1,1,2][2,1,1]]] → 2048

1μu [[[2,2,3][3,2,1][3,3,3]][[1,3,3][2,1,1][2,1,3]][[2,3,3][3,2,3][3,2,1]]] → 3.259

code-golfmathinterpreterarithmetic

Answer 25

Family Tree, Folder Tree

Given a simple family tree in a format reasonably similar to the format outlined below, create a file tree to match it, as explained below.

Input

An ascii family tree in a similar format to the following:

                Grandpa Jim = Grandma Jane
                            |
                 -------------------------------------------------------
                 |          |          |                               |
               Bill Bob     Jim Jane   Sam Sammyson = Aunt Jimbo     Daddy McDad = Mommy McMom
                                                    |                            |
                                                  -----------                    Me
                                                  |         |
                                                Cousin One  Cousin Two

The scheme can be changed within reason, however the test cases provided will meet the following specs:

1. = Symbolizes a marriage
2. If there are any children from a marriage, there will be a | one line below the = symbolizing the marriage.
3. A - character that is below a |, or connected (by adjacency) to a - that is immediately below a | are used to signify multiple children. Below any of these - there may be a |, which will have a the first word of a name immediately below it. This full name is the name of a child.
4. The initial line of the family tree will only contain two people.

This spec maybe should be cleaned up more.

Note that there won't be any relationships more complicated than = marriage or | child linking two names. This means that more complicated relationships, such as divorce or step-children, will not appear in the tree.

Output

There will be no output as such, instead the program/function will create a directory structure matching the input. For example, the above example would lead to the following directory tree:

$ tree family_tree/
family_tree/
├── Grandma Jane
│   ├── children
│   │   ├── Bill Bob
│   │   │   └── parents
│   │   │       ├── Grandma Jane -> ../../../../Grandma Jane/
│   │   │       └── Grandpa Jim -> ../../../../Grandpa Jim/
│   │   ├── Daddy McDad
│   │   │   ├── children
│   │   │   │   └── Me
│   │   │   ├── parents -> ../Jim Jane/parents
│   │   │   └── spouse
│   │   │       └── Mommy McMom
│   │   │           ├── children -> ../../children/
│   │   │           └── spouse
│   │   │               └── Daddy McDad -> ../../../../Daddy McDad/
│   │   ├── Jim Jane
│   │   │   └── parents -> ../Bill Bob/parents/
│   │   └── Sam Sammyson
│   │       ├── children
│   │       │   ├── Cousin One
│   │       │   └── Cousin Two
│   │       ├── parents -> ../Jim Jane/parents
│   │       └── spouse
│   │           └── Aunt Jimbo
│   │               ├── children -> ../../children/
│   │               └── spouse
│   │                   └── Sam Sammyson -> ../../../../Sam Sammyson/
│   └── spouse
│       └── Grandpa Jim -> ../../Grandpa Jim/
└── Grandpa Jim
    ├── children -> ../Grandma Jane/children/
    └── spouse
        └── Grandma Jane -> ../Grandma Jane/

The directory tree must satisfy the following:

1. Create a directory called family_tree that will contain the entire family tree.
2. Inside family_tree/ there will be exactly two directories, these are the two people at the top of the family tree.
3. For every person in the tree, do the following in their directory:
   1. If they have a spouse, create a spouse directory. If the spouse already has a directory named after them, create a link to that directory within the spouse directory. Otherwise, create a directory in the spouse directory with the name of the spouse.
   2. If they have children, then they must have a spouse. If the spouse already has a directory named children, then create a link to that directory and name the link children. If their spouse doesn't already have this directory, create the children directory and add a directory corresponding to each child.

Again, this is a rough draft. The spec needs to be cleaned. I welcome comments

Note that, in all cases, it does not matter where the true directory and where the link is, as long as the link is properly setup. Also, it is okay to create links to other links.

Also, link means symbolic link throughout the challenge.

This is code-golf

Answer 26

The French Farmer in the Dell

code-golf string kolmogorov-complexity

I used to work with kids and The Farmer in the Dell was a popular song among them. Also, I like challenge like 99 bottles of beer or Polar Bear, Polar Bear, what do you hear?. Try them too!

Goal

In your programming language of choice, write the smallest program possible which will output the following text. Output should match exactly, including case, spacing, and punctuation. A trailing linefeed is fine but specify it in your answer. We will play with the french version of the song because I find it more interesting than the english version (also I am french so more memories for me!).

Le fermier dans son pre,
Le fermier dans son pre,
Ohe, Ohe, Ohe,
Le fermier dans son pre.

Le fermier prend sa femme,
Le fermier prend sa femme,
Ohe, Ohe, Ohe,
Le fermier prend sa femme.

La femme prend son enfant,
La femme prend son enfant,
Ohe, Ohe, Ohe,
La femme prend son enfant.

L'enfant prend sa nourrice,
L'enfant prend sa nourrice,
Ohe, Ohe, Ohe,
L'enfant prend sa nourrice.

La nourrice prend son chat,
La nourrice prend son chat,
Ohe, Ohe, Ohe,
La nourrice prend son chat.

Le chat prend sa souris,
Le chat prend sa souris,
Ohe, Ohe, Ohe,
Le chat prend sa souris.

La souris prend son fromage,
La souris prend son fromage,
Ohe, Ohe, Ohe,
La souris prend son fromage.

Le fromage est battu,
Le fromage est battu,
Ohe, Ohe, Ohe,
Le fromage est battu.

If you are french, you may note that I replace all é with e. It is not important for the challenge and I prefer to stay full ASCII.

If you want to code while listening to the song, you can find it on YouTube. :)

Sandbox Questions

A not so difficult challenge. I originally thought about posting it directly, but I prefer to share it first. I don't think test case are needed. I implemented both the english and french version and the last one is far better to my taste :)

Answer 27

Fix Pokemon Go's Servers code-challenge

Background

As you may or may not be aware, Pokemon Go's servers have not fared well under the stress of the game's extreme popularity. As an amateur programmer, I'm in the sweet spot where I know just enough to think I can solve all of their problems, but not enough to be able to understand how complex their problems actually are. Thus, I find myself constantly thinking "Why didn't they just do <insert naive suggestion here>? It would fix everything!" This challenge is focused on one of those probably-useless ideas I've thought up.

First, some very quick background, in case you haven't played the game (you can skip this paragraph if you have): In the course of gameplay, Pokemon can randomly appear at certain real-life locations. Every player in the same location sees the same Pokemon, and multiple players can catch one Pokemon.

One potential difficulty I see with this is storing all of that data. With millions of concurrent players, the game servers have to keep track of millions of Pokemon. That's a lot of IO for their database. Fortunately, I, a graduate of not one, but two introductory CS courses, have a solution! Because player interactions have nothing to do with where and when Pokemon spawn, it is essentially deterministic. This means that it should be possible to drop the database entirely (at least for this one specific task), and replace it with a function! This function could take the player's location, the current system time, and a random seed as input, and return a list of all Pokemon within a certain radius. Because no database lookup is needed, this function would be lightning fast and easily scalable to millions of players.

The Challenge

Your challenge is to write this function. Obviously, the actual game of Pokemon has way too many details to make a feasible code challenge for PPCG, so here's the simplified guidelines:

• Create a function that takes the following inputs, in any format you like:
  • Player location, as 2D coordinates
  • System time
  • Random seed
• The function should return a list of nearby Pokemon, with the following requirements:
  • "Nearby" means "within one unit of distance of the player", where distance is 2d euclidean distance. (Just ignore the edge case where the location is on a round planet)
  • Each Pokemon should have a species and an exact location
  • This list can be in any format you want
  • The results are deterministic (i.e., for the same location, time, and random seed, the same Pokemon are always returned)
  • The Pokemon should persist for some pseudorandom amount of time
    • Thus, if the function is called twice with the same location and random seed, and two times that are very close, then each Pokemon returned the first time should have a large possibility of being returned the second time
  • If the function is called twice with the same time and random seed, and two nearby locations, then any Pokemon that are near both locations should be returned both times
  • The Pokemon should be somewhat evenly distributed across the "world" (the coordinate plane).
    • The Pokemon should be distributed such that at any location and time, the probability of finding exactly n nearby Pokemon of any type is (0.5)^(n+1)
    • Thus, there is a 50% chance of finding no Pokemon at all, a 25% chance of finding exactly 1, a 12.5% chance of finding exactly two, etc.
    • Your algorithm should be capable of returning up to 10 nearby Pokemon, but is allowed to return more, as long as it follows the right probability distribution
• Sandbox question: I want a requirement to be that the algorithm can't simply generate all of the Pokemon in the world and then just return the nearby ones, but I don't know how to formally state this. I had some fleeting thoughts about O(1) memory usage, but that method could strictly speaking have O(1) memory usage if the world is a constant size (which I'm pretty sure it is).

Might this make a good fastest-code challenge? That would fit in with the premise, and might produce some interesting algorithms.

For the sake of making this challenge somewhat reasonable, the list of possible Pokemon and their probabilities of appearing will be small:

• Weedle: 60%
• Charmander: 30%
• Blastoise: 10%

Scoring

This is part of what I need help with in the sandbox. How should I distinguish two entries that both meet all of the requirements?

---

Thanks for reading this far! I know this question isn't nearly ready to be a real challenge. At the very least, it need more specific requirements. But I figured I'd post what I currently have in the sandbox to see if it's worth continuing with. I've never posted or participated in a PPCG challenge before, and I'm sure that's obvious, but hopefully with your help, I can refine this to the point of being a legitimate challenge.

Answer 28

Punch Buggy Probabilities

code-golf

A popular game among children in the USA is "punch buggy", and as with every such game, there are many variations. The one we'll consider for this challenge goes like this:

• The moment anyone sees a Volkswagon Beetle (the "buggy"), participants may punch each other (usually in the shoulder or upper arm).
• A punch must be accompanied by "punch buggy <color>!", where <color> is the color of the VW Beetle (red, green, black, gray, yellow, etc.).
• Whoever makes contact first gets priority (and for this challenge, there are no ties).
• Once person A punches person B, B cannot punch A back (usually accomplished by saying "no punch back!").
• Punches may occur between any pair of participants (for this challenge, every pair of participants).

The challenge

Assuming all possible punching configurations among n people are equally likely to happen, what is the probability of any particular punching configuration? To put it another way, for each distinct punching configuration, how many ways can it occur?

Rules

• Input is a single positive integer greater than 1.
• Output must be one of the following: A) a list of decimals, B) a list of fractions (simplified or not), or C) a list of counts. META: Should I allow these lists to be unordered, or should I require that they be associated with punching configurations somehow? I'm leaning towards the former since it seems like it'd be a headache to figure out how to specify the latter and it would likely be an extra task that doesn't really have anything to do with the core problem.
• Standard code-golf rules apply, and standard loopholes are banned.

Test cases

Input
Output A
Output B
Output C

2
1.0
2/2
2

3
0.75 0.25
3/4 1/4
3 1

Explanation of input 2: With only two people, there are exactly two possible ways: either A punches B or B punches A. These are equivalent, so the probability is 1.0, the fraction is 2/2, and the count is 2.

Explanation of input 3: There are two distinct punching configurations: A -> B -> C, A -> C; A -> B -> C -> A. The latter has only two varieties (the other is A -> C -> B -> A) and the former has six, since there are three choices for the person who punches two others and then two choices for the remaining pair. Thus, the probabilities are 0.75 and 0.25, the fractions are 3/4 and 1/4, and the counts are 3 and 1.

META

• I want to add 4 to the test cases, and I think I'm gonna need help on it since I'm having a hard time counting all 2^6 = 64 possibilities correctly.
• Any clarifications/corrections?

Answer 29

Teh Scrolling Codez

In many movies, computer often appear to be scrolling through some code. We should automate this process to make it easier. Your job is to write code that displays to a graphical console a scrolling view of its own source code. You have two options...

---

You may horizontally scroll the source as HTML's Marquee.

You also may vertically scroll through the source as if the source is code is on a cylinder, and only a fixed number of lines can be displayed

---

Sandbox Questions

Should this be a code golf or pop-con. Pop-con's could result in more visually pleasing solutions. quinegraphical-outputcode-golf or [tag:popularity contest]

Answer 30

image-processingcode-challenge

Autonomous Vehicle

I need a brain for my self-driving car. Something that will take still frames from the front-facing camera and give the navigation system commands. Obviously, if my car is driving me somewhere, I don't want to stop. However, I also don't want to:

1. Kill someone
2. Die

Knowing myself, we can assume that:

• At the speed I drive, hitting the curb or otherwise leaving the road will kill me and thus violate Don't #2

• With my luck, running a stop light, will violate Don't #1 or #2 or both

• Also hitting a pedestrian (or another car) violates Don't #1 (and possibly #2)

Input

The program/function should take an image as input. How it does this is flexible.

Output

The program/function should output one of these commands; ideally, one of the commands that doesn't result in one of the Don'ts being violated.

╔═════════╤═══════════════════════════════════════════════╗
║ Command │ Navigational Outcome                          ║
╠═════════╪═══════════════════════════════════════════════╣
║ Forward │ No course correction, continue straight ahead ║
╟─────────┼───────────────────────────────────────────────╢
║ Left    │ Veer left                                     ║
╟─────────┼───────────────────────────────────────────────╢
║ Right   │ Veer right                                    ║
╟─────────┼───────────────────────────────────────────────╢
║ Stop    │ Screech to a grinding halt                    ║
╚═════════╧═══════════════════════════════════════════════╝

Specifications

• Take an image as input in someway
• Output a command [ Forward, Left, Right, Stop ]
  • Commands can be aliased as [ 0, 1, 2, 3 ] respectively
  • Returning one valid command and no invalid commands is sufficient to pass a test
  • Stop is only valid iff every other command would violate one of the Don'ts
• Rules for valid commands:
  • No running stop lights
  • No running over people
  • No running into vehicles
  • No running off the road
  • If a command does not violate any of the above, then it is valid
• Program/Function must be deterministic

Scoring

Lowest score wins! The scoring function is:

• ( # of Bytes ) / ( Number of Passed Tests )

For example, a 450 byte Python solution that passes 2 test cases earns a score of 450 / 2 or 225.

---

Test Cases

1. Valid Commands: Forward

2. Valid Commands: Left, Right

   • Straight ahead there are pedestrians crossing

3. Valid Commands: Forward, Right

4. Valid Commands: Forward

5. Valid Commands: Left, Right

6. Valid Commands: Stop