Sandbox for Proposed Challenges

Question

This "sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to main. This is useful because writing a clear and fully specified challenge on your first try can be difficult, and there is a much better chance of your challenge being well received if you post it in the sandbox first.

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Answer 1

Pi, continued

The task: generate an arbitrarily precise rational approximation to pi by using a continued fraction.

One way to calculate pi is by using this continued fraction (from Wikipedia):

The first few approximations can be calculated as follows:

You may not use this particular continued fraction. The reason is that in order to calculate this sequence to arbitrary precision, you have to already know pi to arbitrary precision. The series [3,7,15,1,292,...] does not repeat, like pi's own digits.

However, there are continued fractions that have a regular structure. You may use any of these you wish (like these on Wikipedia) in your program.

The rules

• Input: a single, non-negative integer n.
• Output: the nth (improper) fraction in your chosen continued fraction series, in lowest terms.
• Output may be in any form, provided that these conditions are met: 1) the same base is used for numerator and denominator (and for all fractions), 2) the numerator and denominator are clearly distinguishable, and 3) the numerator comes first.
• Your program must use a continued fraction. It may not use any summation series like the approximation formulae here on Wikipedia.

Meta

• I feel like some of this may be confusing. What can I clear up, and how?
• Is it misleading to introduce continued fractions by using an unpredictable series when I want users to use ones that have a regular structure?

Answer 2

Rotate / Flip a Unicode Box Drawing

Given a Unicode box drawing, followed by a series of rotate and/or flip commands, output the result of those operations on the drawing. For clarification, a box drawing can be made from the following characters:

─ │ ┌ ┐ └ ┘ ├ ┤ ┬ ┴ ┼
═ ║ ╔ ╗ ╚ ╝ ╠ ╣ ╦ ╩ ╬
    ╒ ╕ ╘ ╛ ╞ ╡ ╤ ╧ ╪
    ╓ ╖ ╙ ╜ ╟ ╢ ╥ ╨ ╫

The rotate and flip commands are also presented using Unicode symbols:

↔  Flip the drawing horizontally
↕  Flip the drawing vertically
↷ Rotate the drawing 90° clockwise
↶ Rotate the drawing 90° counter-clockwise
↯  Convert all single lines to double and vice versa (Optional - 10% bonus)

All other characters should remain unchanged, but moved to fit where they would be in the modified drawing. For example, if given the inputs:

Input   Output          Input   Output
 ┌┴╖     ╓┴┐             ┌┴╖     ╔═╕
 │A║     ║A│             │E║     ╣E├
 ╘╦╝     ╚╦╛             ╘╦╝     ╙─┘
 ↔                       ↔↷

 ┌┴╖     ╒╩╗             ┌┴╖     ┌─╖
 │B║     │B║             │F║     ┤F╠
 ╘╦╝     └┬╜             ╘╦╝     ╘═╝
 ↕                       ↷↔

 ┌┴╖     ╓─┐             ┌┴╖     ╔╩╕
 │C║     ╣C├             │G║     ║G│
 ╘╦╝     ╚═╛             ╘╦╝     ╙┬┘
 ↷                      ↶↶

 ┌┴╖     ╒═╗             ┌┴╖     ╔╩╕
 │D║     ┤D╠             │H║     ║H│
 ╘╦╝     └─╜             ╘╦╝     ╙┬┘
 ↶                      ↔↕

The drawing may be of any size (let's say anywhere from 1×1 to 50×50), and not necessarily square.

The flip and rotate commands will always occur after any drawing to be flipped, and by themselves on one single line. They should be executed from left to right. (Note that order matters - the E and F examples use the same two commands but in reverse order, and produce different results.)

There may be an arbitrary number of flips and rotates, but you'll note that there are only 8 possible end-states for the final drawing. The G and H examples show two different sets of commands that produce the same result (other than the letter in the middle). It is possible that a series of commands will result in simply returning to the original drawing.

Input may be supplied via command line, user input, file I/O, or any other means you see fit. (Though it should obviously support multiple lines of input. You may use \n to represent line breaks if your input mode only supports a single line.) Likewise, output may be to the screen or a file at your discretion.

This is code-golf, so shortest code wins.

Some more complicated examples:

Input    Output        Input    Output
          ┌─┐                    ┌─┐
          │A│                    │B│
┌─╥─┐     ╞═╡          ┌─╥─┐     ╞═╡
│A║B│     │B│          │A║B│     │A│
└─╨─┘     └─┘          └─╨─┘     └─┘
↷                     ↶

   Input           Output
┌─┐╔═╗╒══╓──    ──╖══╕╔═╗┌─┐
├─┘╠═╝│  ║ ╖    ╓ ║  │╚═╣└─┤
│  ║  ╘══╙─╜    ╙─╜══╛  ║  │
↔

┌─┐╔═╗╒══╓──    ╔═╗┌─┐╓──╒══
├─┘╠═╝│  ║ ╖    ╠═╝├─┘║  │ ╕
│  ║  ╘══╙─╜    ║  │  ╙──╘═╛
↯

┌─┐╔═╗╒══╓──    ┌─┐╔═╗╒══╓──
├─┘╠═╝│  ║ ╖    ├─┘╠═╝│  ║ ╖
│  ║  ╘══╙─╜    │  ║  ╘══╙─╜
↔↯↷↷↕↶↯↶↕↔

Answer 3

Create a spiraling image

popularity-contest graphical-output image-processing

Introduction

WIP

Task

Given an image, output the image with a spiraling effect.

Scoring

This is a popularity-contest, so the submission with the highest number of votes wins!

Test cases

Note that your program should work for images with any size. The output should be a 512×512px image. Also, note that the test cases are examples, you may use any algorithm to produce these images and do not have to match the images below. Use your creativity!

Test case 1

Becomes:

Test case 2

Becomes:

Test case 3

Becomes:

Test case 4

Becomes:

Test case 5

Becomes:

Important

The full size images:

• Test case 1
• Test case 2
• Test case 3
• Test case 4
• Test case 5

Answer 4

Random Physics Golf #1: Net Gravitational Force code-golf math

Introduction to the Series

Every week or so I will be posting a physics challenge. My goal here is to design challenges that in the end, teach some people some physics. Overall, the challenges will be very basic with little information. All of these challenges will have the minimal information necessary to solve them, and the goal is for users like you to do some research, watch some videos, and understand how these concepts work to teach you how to approach these types of physics problems and explain how they work. Of course, I will also give two optional hints per challenge, which are there if you do not have the time or determination to do the research, or you cannot figure out how to do the problem after researching. The two hints will be "necessary equations for this challenge" and "process to solve the problem". The hints are completely optional to use and it is encourages to not use them, but as stated above to learn the information for yourself. The series will have one main leaderboard. Whoever has the least combined byte count for all of the challenges gets a to be determined prize. Each challenge will range in difficulty, with an upwards trend of difficulty. I wish you all luck and I hope you learn a thing or two!

Challenge #1: Net Gravitational Force

Note 1: this challenge highly requires knowledge of the mathematical vector quantity, if you do not know what that is, I suggest reading this and this before attempting this challenge.

Note 2: this challenge considers gravity in CLASSICAL MECHANICS. Disregard general relativity for this challenge.

Lets start with the definition of a force. A force is a vector quantity, a number with both direction and magnitude. Simply put, force is mass times acceleration. Many mathematicians will know the name of this formula as Newton's Second Law. Now, that is a well known formula, but here is something less known: all forces are classified in one of four categories: weak nuclear, strong nuclear, electromagnetic, and gravitational. These four are called the four fundamental forces of the universe. We will be focusing on the gravitational force in this called.

The gravitational force is then classified as a field force. This means that the force acts on all objects in a certain radius around another object. In this case, gravity pulls down on objects from anywhere in a radius around them. However, I still have not defined where gravity comes from. Well, the simple answer is from mass. An object with more mass has a bigger gravitational pull on objects around it. In case you are wondering, the earth has a gravitational pull of -9.81 m/s^2 (an object will gain 9.8 m/s of downward velocity every second). But here is where it gets fun: because gravity comes from mass, every object with mass has a gravitational pull. This is where you come in. I want you to calculate the net gravitational pull of all the objects surrounding another object. Here is a better explanation:

You will receive co-ordinates and masses of objects in space for input. So an example input could be visualized as this: You can easily see each force being applied on the target object by the three larger objects. Objects will smaller masses have a smaller gravitational field (as shown by the orange force arrow). Your job in this challenge is to find the net gravitational force being acted on the target object. To do this, it is a simple vector addition problem with the forces from the other objects. So, the resultant vector (net force), may look something like this: This is all of the information that I will give you. It is now your job to find the equations, and research how this all works.

Challenge Specs

• Input will be several lists of numbers consisting of the x co-ordinate, y co-ordinate, and mass of each object. The numbers could be either integers or decimals. You may take this in any convienent format ([[1 2 3][4 5 6][7 8 9], [(1,2,3),(4,5,6),(7,8,9)] and 1,2,3|4,5,6|7,8,9 are all acceptable. The first list of inputs will always be the target object (red in the pictures above), and the other lists will be the other objects. All inputs will have at least two objects. No objects will have the same co-ordinates.
• Output will be two numbers, in any human-readable format, in any order. One will be the magnitude of the net force, using your desired unit system (SI, Planck units, Imperial units, etc.) and the other will be the direction in radians OR degrees of the net force. Output must be precise to the least number of significant figures in the input (Input: 2, 3.5, 6.1 -> Output: 200 (232.34 before rounding), note this is not an actual test case). Output may or may not be in scientific notation, its up to you.
• You may assume input will not cause any error during execution, and you may assume all inputs will be valid.

META NOTE: Help me decide the precision of the output: http://strawpoll.me/6825341

Test Cases

Meta Note: WIP

Hints

These hints are for those who do not want to put in the time and effort of research, or those who could not find a solution. So, here are the two hints:

Hint 1: Equations:

You need the following equations for this challenge:

You will also need the standard vector equations for this challenge:

Hint 2: Sample Solution Process:

It would take up too much space to fit it all here, so I made this to aid you for this hint.

Leaderboard

Meta Note: blah blah blah, working leaderboard will eventually go here! This leaderboard will contain and combine scores for all of the weekly challenges. It will only be visible on this question, though.

Answer 5

Temperature in a line of rooms

You have a line of rooms that are different temperatures.

      1       2       3  
 1.2  |  3.5  |  4.0  |  3.7

The doors between adjacent rooms start out closed. When you open a door, the now-connected rooms average out their temperatures. For example, opening door 2 gives

      1       2       3   
 1.2  |  3.75 _  3.75  |  3.7

Then, opening door 1 equalizes the first three rooms to their average (1.2+3.75+3.75)/3 = 2.9

      1       2       3   
 2.9  _  2.9 _  2.9  |  3.7

Finally, if we close door 2 and then open door 3, the last two rooms will average out without affecting the other rooms.

      1       2       3   
 2.9  _  2.9 |  3.3  _  3.3

You can think of the instructions to open and close doors as a sequence of toggles that switch between open and closed, here 2, 1, 2, 3, with the doors starting closed. Given the initial temperatures of the rooms and the sequence of door toggles, output the final temperatures. Fewest bytes wins.

Input:

• A list of initial room temperatures, which are positive reals. There will be at least two rooms.
• (Optional) The number of rooms n.
• A list of doors to toggle in order, which range from 1 to n-1. Optionally, these may be zero-indexed.

Output: The list of final room temperatures to some reasonable precision.

TODO: Test cases.

Answer 6

Senior Prank

We're graduating to a full site soon, and there's only one thing left to do before graduation: pull a senior prank! I think we should do a variation on the classic "fill a hallway with cups of water" gag.

Challenge

Your program will read in text and output that text, covered in upside-down cups of water. An upside-down cup of water looks like this: /~\
These cups can only be placed in whitespace in the input, and can only be placed so that all three characters of the cup are directly above a non-whitespace character (otherwise the water would spill out!). Cups cannot be stacked on top of other cups. Cups must be placed in every available opening, and it is assumed that every input is surrounded by an infinite field of whitespace.
We need to pull the prank off quickly and without anyone noticing, so fewest bytes in each language wins.

Test Cases

Input:

     ____________________________________________
    /   ___    /   ___    /   ______/   ________/
   /   /__/   /   /__/   /   /     /   /_______
  /   _______/   _______/   /     /   //__    /
 /   /      /   /      /   /_____/   /___/   /
/___/      /___/      /_________/___________/

Output:

     /~\/~\/~\/~\/~\/~\/~\/~\/~\/~\/~\/~\/~\/~\
     ____________________________________________
    /   ___    /   ___    /   ______/   ________/
   /   /__//~\/   /__//~\/   /     /   /_______
  /   _______/   _______/   //~\  /   //__    /
 //~\/      //~\/      //~\/_____//~\/___//~\/
/___/      /___/      /_________/___________/

Input:

 L
LOL  ROFL:ROFL:LOL:ROFL:ROFL
 L\\        ____I____
    ========    |  |[\
            \___O==___)
            ___I_I__/

Output:

 L   /~\/~\/~\/~\/~\/~\/~\
LOL  ROFL:ROFL:LOL:ROFL:ROFL
 L\\/~\/~\  ____I____
    ========/~\ |  |[\
            \___O==___)
            ___I_I__/

Answer 7

king-of-the-hilljavascript

City Life

A cellular automation war game.

In this game, each player will control group of cites on a grid. Each city takes up one cell, and all cells with no city are "wilderness", and have no owner. The game will consist of a series of rounds, called "generations". Play continues until a player gets 1000 points, or 200 rounds, whichever happens first.

Setup

The board will start with one city controlled by each player. It will be square with sides length ceil(sqrt(25*n)) for an n player game. Cities will be placed randomly in such a way that no two cities will see each other the first round.

Phase 1: give orders

At the start of each generation, each city gets n actions where n = # of adjacent wilderness spaces + 2. So a city surrounded by wilderness gets 10 actions while a city surrounded by cites gets only 2. The Actions will be divided into these three categories:

Attack/Spread : used to Attack Cites or spread into the wilderness.

• Takes a direction as a parameter. Will add one "Attacker" to that cell, even if the cell is a city with the same owner. (See resolve attacks)

Defend : used to protect your city.

• Will add one to the defender count of the city performing this action. (If no defend actions are used, the city will become wilderness.)

Score : used to win.

• Adds one to the score the cites owner.

Phase 2: resolve attacks

After all cites have put in orders, all cells are checked for takeover.

• A wilderness cell will become a city if at least three attackers are there. The new city's owner will be determined randomly from among the attackers.(for example, if player A sent 2 attackers and player B sent 3, than A has a 2/5 chance of owning the new city)

• A city will become wilderness if the number of attackers is equal to the number of defenders (even if both are 0).

• A city is taken over if their are more attackers than defenders. The city's new owner is determined randomly from among the attackers, as above.

After the round is complete, all attackers and defenders are reset.

---

To enter the competition, you must create a bot to perform the "give orders" step. All bots will be written in JavaScript.

I/O

You will provide a character to represent your city and a function that takes as parameters:

1. Your vision. each city can see a 5x5 square with the city as its center. It will be represented as an array of arrays of characters, " " representing wilderness, and each players character to represent their cites.

Example:

if you have a map like This ("Y" represents you)

+-----+   
|AA  B|    N
|A    |    ▲
|  YY | W< O >E
|C   C|    V
|   C |    S
+-----+    

Your sight parameter will be:

[["A","A"," "," ","B"],["A"," "," "," "," "],[" "," ","Y","Y"," "],["C"," "," "," ","C"],[" "," "," ","C"," "]]`

2. The number of actions you can perform this turn. (which can be calculated, but I will give it to you as most bots will need it.)

You must return an array of strings, each string representing an order.

"N" - Attack North

"NE"- Attack North east

"W" - Attack West

...

"D" - Defend

"$" - Score

If you return more moves than you have actions allotted, the moves at the end of the array will be ignored. If you have less, extra moves will be set to "D".

---

I have made a controller that is reasonable, although I would like add to it and finalize the rules before publishing. If you have any advice or criticism, please comment below.

---

Example Answer:

---

Random Bot [?]

function(map, moveCount){
    var allMoves = ["N","S","E","W","NE","NW","SE","SW","D","$"];
    var orders = [];
    while(orders.length < moveCount){
        orders.push(allMoves[Math.floor(10*Math.random())]);
    }
    return orders;
}

This bot will just assign a random move for each action. Its cites are represented by ?.

Answer 8

Super Smash Bots

king-of-the-hill

This is an idea for a KOTH based off of the Super Smash Bros video game series by Nintendo.

The basic mechanics of this KOTH would be an every-man-for-himself battle between a large number of players simultaneously. Players can execute a variety of moves, like short/medium/long-ranged attacks or blocking. As opposed to most combat-based games, players do not have a health bar, but rather die when knocked off of the stage (the arena). When an attack hits a player, it deals damage to that player but also causes knockback. The amount of knockback a player experiences is proportional to the total amount of damage he's received so far in the game.

The Arena

The game takes place on a vertical stage with gravity. There will be several fixed platforms surrounded by empty space. A player too far from a platform is killed. More ideas about the design of the stage are covered in the Stage Design section.

Character Selection?

The actual game offers players the selection of different characters, each of which have different abilities, strengths, and weaknesses. If I am to include character selection, that will be a way for players to pick the strategy they think works best and choose a bot that has those strengths. Another KOTH which had this feature was the Pokemon-themed KOTH (citation needed).

On the other hand, balancing stuff can be hard.

Actions

• Move. Simple as that. Well, not exactly. I think this could make a very good contender for a continuous-surface (not a grid) area. On a surface, the character would walk, while airborne, the character's movement doesn't respond as quickly.
• Jump. Is like a move, but vertical. More specifically, this gives the player an upward velocity. Double jumping might be possible.
• Short Range. This deals damage to an immediately adjacent player.
• Medium Range. This deals damage to players within a certain range. It would likely involve your player physically moving as well.
• Long Range. This creates a projectile, which can deal damage to a player in the specified direction, no matter the distance.
• Area of Effect. All players within a given range take a little damage.

Respawning?

Is is often typical that players have three lives, and thus must be killed three times to be eliminated. By respawning players, the variance of each match outcome should be reduced.

Game Ticks

If I'm doing a continuous-field, then I would want something the emulates continuous movement. In order to give fair processing time, I can't really have all of the entrant programs running at once in an asynchronous fashion. Some possible solutions are as follows.

1. Priority Queue
   • Each action taken creates a certain time delay before the player can move again. Standing still is shortest delay, moving is second-shortest, and long-ranged attacks have the longest delay.
   • Turn order is determined by a priority queue. From the list of players, the player with the least delay is selected. Then, the game's physics are simulated for that amount of time ("virtual" time, not "true" time) and that much time is subtracted from everyone's delay. The selected player picks an action, and he is put back into the queue with that move's delay.
   • This creates a period of vulnerability after an attack which may be game-mechanically interesting.
2. Random Time-Steps
   • Play occurs in a semi-random order, with random, non-uniform time-steps between moves. This makes it so that the player cannot predict exactly what the world will be like in the future, or guarantee the exact timings of any moves.
   • After each player has taken a single move, the order of players would be scrambled.
   • Time-step duration would be approximately constant with a random variation of +/-20% or something like that.

Animation

This would be really cool to watch, but I don't think I could possibly animate this by myself.

Stage Design

Stage design will be important, because a large chunk of the entrant programs will be tailored the stage. I don't really have any clue what I'm doing here.

One idea I've had is to crowd-source the stage design.

Maybe something with a few ledges, like this? (scaled down for ASCII-artability)

..........................
..........................
...XXXX...................
...............XXXXXXX....
..........................
....XXXXXXXXXXXXX.........
..........................

I could add some more features like so:

..........................
....XXXX..................
........XXXXX.....XXXX...
......................\...
..XXXXXXXXXXXXX....XXXXX..
................../.......
............XXXXXX........
..........................

The slants represent ramps that the player could walk up.

Player Navigation

I foresee one of the most difficult things for entrants to do is to navigate the stage. Each player would definitely receive a copy of the current stage and players as input every turn (or as arguments/parameters, more details on that below).

I may choose to offload a bunch of pathfinding stuff onto the controller so that entrants, if they so desire, can give the destination and have their character move there. Given that the stage would be constant, this should not be difficult for the controller to do. On the other hand, the continuous-field design can make pathfinding more complicated.

One thing to consider during stage design is the ease of pathfinding.

Vertical or Horizontal?

Pretty much the whole proposal has been assuming a vertical map. I could change this to horizontal to allow a larger number of people to fight in one match.

Classes or Full Programs, and Language?

Personally, I think this would be easiest to do as a Java KOTH with classes. It will run quick(-er than several other methods) and I could give entrants access to a variety of methods that give information about the stage.

Controller

Literally no work has been done yet.

Answer 9

Golf all the 16 logic gates with 2 inputs and 1 output!

This question asked for 16 independent functions. I would like the opposite: a single function that takes an additional parameter that specifies which of the 16 logic gates is required using an integer from 0 to 15. If you don't want to use a 0-based index of the list in the linked question then you should specify which integers map to which logic gate (but they should still be 0 to 15).

Examples:

 0,0,0  falsey
 1,0,1  falsey
 2,1,0  truthy
 3,1,1  truthy
 4,1,1  falsey
 5,0,1  truthy
 6,1,0  truthy
 7,0,0  falsey
 8,0,0  truthy
 9,0,1  falsey
10,1,0  truthy
11,1,1  truthy
12,1,1  falsey
13,0,1  truthy
14,1,0  truthy
15,0,0  truthy

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

Answer 10

Fireworks code-golf ascii-art

---

Make me some fireworks !
And since we are super-late for the 4th make them as quick (read short) as possible !

Input
2 integer, the fuse (any value equal or bigger than 5) and the radius (1 - 2 - 3).

The fuse define the lenght of the tail, the last character of the tail is the center of the explosion. The tail must be centered with the explosion.
The radius define the explosion.

Rule
No need for exception handling, the input will be a valid one.
You may or may not padd your firework, the choice is up to you.
Input, Output and the choice beetwen full program or function is, once again, up To you and your lenguage of choice.
Standard loophole rules apply.
Hopefully no built-in (i'm looking at you mathematica) exist.

Example

fuse 5, radius 1  
     * *    
    * * *
     *|*
      |
      |
      |


fuse 10, radius 3  

   *     *
    *   *
     * *    
* * * * * * *
     *|*
    * | *
   *  |  *
      |
      |
      |
      |
      |
      |

---

while stretching the fuse is not a big deal, ence no limit to it, I found interesting see if it's gonna be cheaper to have hardcoded the strings for the part where the firework cross the fuse or is gonna be cheaper some fancy algorithm, ence I' ve set a limited number of alternative for the radius.

I'm really sorry if my english is bad, I usually can get my idea trought but more than often i stumble with some verbs.

Answer 11

Peter Piper and the Peck of Pickled Peppers

tags: code-golf kolmogorov-complexity

---

Without an introduction, output the following tongue twister:

Peter Piper picked a peck of pickled peppers.
A peck of pickled peppers Peter Piper picked.
If Peter Piper picked a peck of pickled peppers,
Where's the peck of pickled peppers Peter Piper picked?

with or without a trailing newline.

This is code-golf, so shortest code wins.

Answer 12

Transpose a Ragged Array

code-golf

Given an array of arrays of integers where the rows may not be of equal length, pad those rows with nulls, and transpose the array.

Rules

• Use any sane input for the array.
• Specify which null(s) you are using for this function.
• The output should be a transposed array, printed in whatever way is sane for your language.
• This is code golf. Aim for the shortest code possible.

Test cases

I: [[1, 2], [3], [4, 5]]          # Padding with nil here
O: [[1, 3, 4], [2, nil, 5]]

I: [[1], [2, 3], [4, 5]]
O: [[1, 2, 4], [nil, 3, 5]]

I: [[1, 4, 5], [8, 3, 2], [1, 7, 9, 6]]
O: [[1, 8, 1], [4, 3, 7], [5, 2, 9], [nil, nil, 6]]

I: [[1], [2]]
O: [[1, 2]]

I: [[1, 2]]
O: [[1], [2]]

I: [[4, 5, 6, 7], [8, 9]]                  # Padding with spaces here
O: [[4, 8], [5, 9], [6, ' '], [7, ' ']]    # as an example of a different null

As always, if the problem is unclear, please let me know. Good luck and good golfing!

Answer 13

Play a 1D chess variant

in this king-of-the-hill challenge, you must create a bot that plays a 1d chess variant I created, featuring all leaper pieces, and a 15 long board.

Esolangs are encouraged to participate

Game Rules

Goal

To capture the opponents royal (king/queen).

Board

The board is 15 squares long

Player _______________________________ Player
 one   |_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|   two
       player1 side       player2 side

Each player has their side of the board. (note that while playing, you will always be on the left side of the board). You have six squares that belong to you, the opponent has six of their squares, and three squares in the middle are unowned.

Setting up

At the start of the game, you will place your pieces into a configuration of your choice. The pieces will be set independently of each other; this game does not have perfect information. When setting up, you will pick where to place your four pieces, and whether they will be reversed (see next section). You may only place your pieces in your owned squares.

Pieces

There are 4 / 8 pieces; there are 4 distinct pieces, which you can have reversed, and unreversed. I have given them distinct names. Their movements are detailed here.

reversed

reversed means that all the moves of these pieces are reversed in their direction; 2 forward becomes 2 back, three back becomes three forward.

Capture means to move to a space occupied by an enemy piece, and remove that piece from the game. Move means to move to a space occupied by no pieces.

Ascii "diagrams" have been provided. P denotes the piece being showed, $ denotes a space the piece can move to, X a place the piece can capture on, # a piece can move and capture on. Diagrams are the same for both pieces in a pair, because one simply executes the moves backwards.

You must have exactly 4 pieces on the board, and have exactly one from each of the pairs below.

Footman (f)/Coward (c)

The footman may move to an empty space one (1) forward, and capture two (2) forward.

The coward may move to an empty space one (1) backward, and capture two (2) backward.

P$X

Horse (h)/spider (s)

The horse may move to an empty space two (2) or three (3) forward, and move or capture one (1) backward.

The spider may move to an empty space two (2) or three (3) backward, and move or capture one (1) forward.

#P $$

Archer (a)/Trickster (t)

(I doubt anyone will use trickster unironically)

The archer may move two (2) squares backward, one (1) forward, and may capture four (4) steps forward

The trickster may move two (2) squares forward, one (1) backward, and may capture four (4) steps backward

I have included some black and white squares for clarity in distance

# # # #
$ P$  X

King (k)/Queen (q)

Both Royal pieces will end the game when captured.

The king may move or capture one (1) backward

The queen may move or capture one (1) forward

#P

Misc.

Check does not exist: Royal pieces may be left en prise, capture of them results in a win for the capturing side.

There is no (pawn) promotion of any kind

A piece may not attempt to move of the board; the board is a fixed size and does not wrap.

Programs

Programs will take input. When they take input of "0", or a specific input of your choosing, they will output a setup for the game. when they take input "1", or a specific input of your choosing, they will then receive input of the board, and output a move. (the program will be run multiple times)

Moving

To move, you will output the square that the piece is currently on, and the space where you wish to move the piece to, or have the piece capture on. The format is as so (in regex):

[0-9a-e]\n?[0-9a-e]\n?

The board is zero indexed, a piece on the first square is on square 0.

There should be exactly 2 non-newline characters in the output

Input

when it is your turn to move, you will receive input. The input you receive will represent the pieces in the playing field. The input will fit the regex here:

[fFcChHsSaAtTkKqQ ]{15}

Caps represent enemy pieces, lowercase represent your pieces.

when you receive the board positions, you will always have the perspective of player one

WIP, will do more later

Sandbox

What should happen if bots enter an infinite loop? I could just make a draw on a time limit, but that seems not so great, since it is hard for bots to know when they are doing this.

Also just other feedback in general

Answer 14

(-: Emotional Programming ;-)

Write the most emotional program you can, i.e. which consists of emoticons as much as possible.

The program should receive a word and print an appropriate emoticon.

Scoring - I'm really not sure about this, and the question will be worthless without a good scoring algorithm. I want to:
1. Avoid giving an advantage to very short programs (e.g. (-:, is 100% emotional).
2. Avoid a meaningless help of emoticons - print '(-:' #(-:(-:(-: and such.
3. Prefer a variety of different emoticons.

Suggestion:
1. Count characters of code.
2. For each emoticon in the code, reduce a character. 2. For N different emoticons used, reduce further 2*N^2 characters.

What's an emoticon? Anything that somewhat resembles a face, or a closed list?

And should I ban Emoticon?

Answer 15

Create an Autostereogram (Optical Illusion w/ Hidden 3D Shape)

An autostereogram is a type of optical illusion requiring the viewer to, simply put, change distance at which your eyes are trying to view the image. In order to see the hidden image rather than just a nonsensical two-dimensional image, the viewer must either focus their eyes in front of the image (cross-eyed), or behind the image (wall-eyed). Depending on its type, autostereograms may be viewed either way, only cross-eyed, or only wall-eyed. Wall-eyed are the most common.

The illusion below taken from the linked Wikipedia article may only be viewed successfully using the wall-eyed technique. Viewing the full-sized image may help.

The hidden image is:

A shark

I didn't know they were called autostereograms until today, but I always liked this type of optical illusion, since I found the hidden image easy to spot using the wall-eyed technique.

Your goal is to take a depth map and either:

1. Take in an image to modify with the map, then return/display the resulting image
2. Create a random dot autostereogram

The quality of the image must be such that the image is hidden and can be viewed using one of the techniques listed above.

code-golf graphical-output

Answer 16

Generate a Call Tree code-golf graphical-output

Given a C program, generate a graphical call tree.

A call tree is a tree where the nodes represent stack frames, and the connections represent nested function calls. For example, here is a simple C program and its call tree:

#include <stdio.h>

int foo() {
    return 4;
}

int bar(int a) {
    return a + 2;
}

int baz(int a, int b) {
    return a + foo() + bar(a)*bar(b);
}

int main() {
    int a = baz(1, 2);
    printf("%d\n", a);
    return 0;
}

Layout

The layout of a call tree is as follows:

• The top function is always main().
• On the next level below are all of the functions that main calls, in order of calling (top-to-bottom, left-to-right).
• On the next level are all of the functions that those functions call, and so on.
• The leaves of the tree are functions which do not call other functions, or are standard library functions (which are treated as black boxes).
• Each function (with its argument list) is in a rectangle, large enough that the function name and argument list isn't touching the rectangle's borders.
• Rectangles must not touch other rectangles.
• The lines drawn between the rectangles must not touch or cross any line or rectangle other than the two rectangles they are connecting.
• The text must be a monospaced 14-point font.
• The colors of the text, rectangles, lines, and background are not important, so long as all text is one color, all rectangles are one color, all lines are one color, the background is a single color, and everything can be clearly distinguished from the background.

Note that the example image above does not perfectly follow these rules.

Rules

• You may assume that the C program is a valid, standalone program (all functions called are either defined in the input source code or exist in an #included header, and no input is taken from any source).
• Any functions not defined in the input source code are assumed to not call any other functions (this is not the case in reality, but it allows for simplification of the call trees, namely by avoiding implementation-specific details)
• All function calls in the call tree must include the arguments passed.
• main is assumed to not have any arguments.
• There will be no function pointers, gotos, setjmp/jonglmp calls, dynamic memory allocation/deallocation (so no malloc, calloc, realloc or free), or preprocessor macros in the input source code.
• There will be no infinite loops or infinite recursion (all programs are guaranteed to terminate and thus have a finite call tree).
• All arguments will be ints (to simplify matters, since the types don't really matter for this challenge). This means that the example program above would not be a valid input, because of the printf call.
• All functions will either return an int or will be void (non-returning) functions.

Answer 17

Regex Golf Generators

cops-and-robbers kolmogorov-complexity regex

Challenge:

Cops:

The cops must post a 150 byte or less program in any language that outputs between 20 and 200 strings of printable ASCII (this excludes newlines), half of them "match" strings and half "don't match" strings. You can't output an odd number of strings -- there must be one don't match for each match.

The strings can be output as two lists of strings, or one list with a fixed delimiter between the "match" and "don't match" sections. The "match" and "don't match" lists can come in any order.

The following special characters are not allowed in the strings: ()[]*+?.\|^$.

Note that the program must be deterministic, and the language must be revealed.

Robbers:

The robbers must pick a cop answer and submit a regex in any flavor that matches the "match" strings but does not match the "don't match" strings.

The regex must be shorter than min(<length of all the match strings> + <number of match strings>-1 + 4, <length of all the don't match strings> + <number of don't match strings>-1 + 10), as this is the length of the regex that simply hardcodes it: ^(<match string 1>|<match string 2>|...)$ or ^(?!(<don't match string 1>|<don't match string 2>|...)$).*.

The shortest regex posted for that submission wins (note that there can and should be multiple competing cracks for one submission).

Scoring:

The robber's score is simply their number of wins (posted the shortest regex for a given submission) -- higher is better.

The cop's score is max(byte count of winning regex - byte count of submission - 4*(number of match strings - 10) for each submission) -- again, higher is better (you should be maximizing the length of the cracks and minimizing the length of your code). The byte count of the winning regex for an uncracked submission is the length of the hardcoded regex. Self cracks are permitted but must be marked as non-competing and will not count toward your cop or robber score.

The winning cop and robber will be announced 2 weeks after the posting of this challenge. Submissions will be allowed after that, but will not count towards your score.

Answer 18

Machines learning arithmetic

Note: Feel free to take and use this challenge, either the entire challenge as is, or just parts of it.

_{I've made a complete rewrite of this question. I figured the original version was more complex than it had to be. The task is essentially the same. The original challenge text had 4 upvotes and can be found in the edit history.}

---

You will receive 30 lists of integers. Those lists are the result of a polynomial expression y = p(x) = a*x^4 + b*x^3 + c*x^2 + d*x + e, for x in the inclusive range [-1e5, 1e5]. Let's call those lists L1, L2 ....

I reserve the right to make changes to the lists by changing constants and the order if solutions seem to be custom made for those 30 lists.

Challenge:

Your task is to figure out what the constants a, b, c, d, e are for each of those 30 lists.

You will write a code that pulls numbers from each list (one list at a time). It must ask for the y-values for individual x-values, as many as you want, but one at a time. When you think you have enough information, you'll attempt to guess the value of the constants.

You'll do this for all 30 lists.

Scoring:

The lowest score wins!

• You get 1 point for every number you pull from the list
• You get 10 points for every attempt to crack the code (guess a, b, c, d, e)
• The scores for all lists will be added up.

If no submission cracks all lists successfully then the one that cracked the most will win. Tie breaker #1 will be fewest points, tie breaker #2 will be time of submission.

Rules and clarifications:

You can assume all constants to be integers

The lists will be formatted in this way (suppose the expression for L1 is: 2*x). I'm using MATLAB/Octave syntax for a cell array. You can change this to fit your needs (language).

L1 = {[-200000, -199998, -199996, ... -4, -2, 0, 2, 4, ... 199996, 199998, 200000], [0 0 0 2 0]};

You can change the format to fit your needs, but you must not mix the list and the values for a, b, c, d, e.

Example:

You ask for y for four different input values, and get the results:

L1(0) = 0
L1(1) = 0
L1(2) = 2
L1(3) = 12

Your function guesses (for some reason) that this is x^3-2x^2+1, and attempts to crack it:

L1([0, 1, -2, 0, 1]
false

You have tried 4 values, and attempted to crack it once. This gives you 4 + 10 = 14 points.

You try a few more values:

L1(-9) = 6480
L1(-7) = 2352
L1(7)  = 2352
L1(9)  = 6480
L1(100)= 99990000

You're now confident that this has to be: x^4-x^2, and attempt to crack it again:

f([1 0 -1 0 0])
true

You have successfully guessed the constants a, b, c, d, e, and get a score of `14 + (5 + 10) = 29 points.

You have 29 functions left.

---

• I'll have to post the lists on some suitable place (where)?
• Can I ban builtin interpolation functions somehow without risking the "unobservable requirements", "x without y" pitfalls?
• Anything else?

Answer 19

This message is open for anyone to adopt and post to main. For more details, see the chat room or meta post.

Ping an IP address continually and report the dropped to returned ratio

Create a console program that pings an IP address at most once per second and reports the ratio of dropped to returned packets to the screen in real time.

The IP address will be provided on the command line in standard IPv4 notation. (eg. 192.168.0.1)

The 'ping' method should be ICMP echo (See here for a summary of ICMP packet structure) with a packet size of at least 32 bytes.

Your program must be "standalone" and cannot rely on external programs, libraries, or resources.

This is code-golf so let the shortest answer win

Answer 20

Me, Me, Me!

quine code-golf

Edit: changed success when the input matches the source code to when the input is any permutation of the source.

Your code is clearly superior to all other code. In fact, your code is so great that it prints itself when the opportunity arises (but not when any other, inferior code is around.)

Task

Write a program or function that takes a string as input. If the string is equal to some permutation of the characters in your source code, then output the entire source code. Otherwise, output Gross.

If your language uses a non-ascii encoding, "character" is defined as whatever a character in your source looks like. If it's unreasonable to take input in that format, you can treat the bytes of your source as their respective extended ascii codes.

Input

Takes a string using whatever input mechanism your programming language provides.

Output

Prints either the entire source of your program or the word Gross. No additional output is permitted.

Rules

• You can take input using any reasonable method. (Stdin, function parameter, etc.)
• A string a is a permutation of a string b iff each character in the alphabet appears the same number of times in a and b.
• This is code-golf Shortest code (in bytes) wins.

Answer 21

What is your Operating System?

I can't believe we haven't had this one before

To avoid any doubts about what constitutes a separate OS, you must return an index into your chosen subset (containing minimum two) of the following OS families. You may order your set as you like, so include your ordered set, and state if you use zero or one based indexing. You may also bunch together families you cannot distinguish between.

  Windows, Minix, Linux, macOS, BSD, HP-UX, AIX, Solaris, Unix, Z/OS, OS/2, QNX

Your score is your byte count divided by the square of the number of indices your code can return – given that it is run on the appropriate OSs, of course.

You do not have to account for virtual machines, emulation layers etc., e.g. WSL and Wine.

Examples

Your code can detect Windows, macOS, AIX, and Linux. It returns 0 for Windows, 1 for macOS, 2 for AIX, and 3 for Linux. Your score is a sixteenths of your byte count.

Your code can distinguish between Z/OS, OS/2, and UNIX/Linux/AIX. It returns 1 for Z/OS, 2 for OS/2, and 3 for any UNIX-like OS. Your score is a ninth of your byte count.

code-challenge

Answer 22

One OEIS after another

Answer 23

Invisible Ink, Easy code-golf

In the physical world, invisible ink usually becomes invisible when it dries, and is then is readable if it is exposed to heat or chemicals of some kind. The invisible ink in this challenge will be readable when exposed to highlighting.

Create a full program or function that takes in text from the console (using a prompt) and outputs it the console so it cannot be seen unless highlighted.

Notes:

• Assume that the console is a solid color (black, white, green, etc.).

Answer 24

Let's play Othello (Reversi)! king-of-the-hill

Open for takeover

I don't have the time to devote to this right new, and not for the foreseeable future. Anyone who wants this idea, the post, and any code I have in the repo should comment below.

Side note on the code, I have a gorilla repl file in the repo that I can use to run test games on, and get screenshots of during any point of the game. If you want I can make up screenshots for the rules section since I have everything setup on my end for that.

---

This would be a king of the hill about reversi. Yep. I'm going to write up the post and controller later The controller is being written here: https://github.com/JJ-Atkinson/reversi-koth-ppcg , but I'm putting this here so show the idea is taken ;)

---

Post start

Rules

(you can probbably skip this if you've played Reversi before)

(images from http://www.coolmath-games.com/0-reversi)

Reversi is a two player game with a simple goal - own the most pieces on the board.

Wikipedia

Answer 25

Prime encode integers!

code-golf

In this challenge, you must convert inputted natural numbers into a prime encoding.

The sequence of the primes, and 1, is a complete sequence (We're going to consider 1 an honourary prime for this challenge). What this means is that it's possible to express any positive integer as a sum of the terms of the sequence (without reusing terms). For example, the powers of two are a complete sequence, and you can encode numbers in them (this is binary).

As with binary, you use a sequence of 1s and 0s to represent which terms are used. 1011 will represent 5 + 1 + 2, or 8. 8 could also be represented as 10001, or 7+1. the place values represent primes:

... 13 11 7 5 3 2 1

continuing with all of the primes to the left

In this challenge, you must output a string of 1s and 0s, such that the place value primes sum to inputted strictly positive integer

Test cases

8 -> 10001 or 1011
2 -> 10
11 -> 1111 or 10101 or 100000 (I might have missed one of the possibilities?)
13 -> 1000000 or any other possibility

you may use any valid representation of the in

input note:

input is 1 strictly positive integer

you do not need to consider the value 0, even though it is possible to represent in this system, by just outputting zero

Answer 26

Find the longest Factor-Multiple sequence

Inspired by this riddle.

A Factor-Multiple sequence is any sequence where A[n+1] is either a multiple or factor of A[n].

Task

Create a full program or function that, given a list (or any other accepted input) of positive integers, returns (one of the) the longest possible Factor-Multiple sequence containing those numbers. Each number can only be used once and each number in the input will be unique.

Input

As mentioned above, input is a list of integers. If your language only supports strings, or if you like doing so, you may take input as strings instead.

Output

You can output your sequence in any way you like as defined on meta.

Rules

• This is codegolf, shortest code wins.

Test cases

More need to be added.

Input                                                Output                 
1 2 3 5 7 11                                         2 1 3 or 3 1 2 or 11 1 7 etc.
1 2 3 4 5 6 7 8 9 10                                 5 10 1 4 8 2 6 3 9  

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20   11  1  7 14  2  8 16  4 12  6 18  9  3 15  5 10 20 

Meta:

• Need to add more test-cases

• Can't think of any relevant rules, did I miss any?

Answer 27

I'm symmetric, not palindromic! code-golf string

Background

Inspired by I'm a palindrome. Are you?, where it is presented the shocking fact that “()() is not a palindrome, but ())(”, I asked myself what instead is ()() and the answer is simply: it is a string with a vertical symmetry axis!

The task

Write a program or function that takes a string S (or the appropriate equivalent in your language) as input, checks for symmetry along the vertical axis, and returns a truthy or falsy value accordingly. You can use any reasonable means to take the input and provide the output.

Reflectional symmetry

Reflectional symmetry around a vertical axis (or left-right symmetry) means that if you put a mirror vertically at the exact center of the string, the reflected image of the first half of the string is identical to the second half of the string.

For example, the following strings are reflectional symmetric around a vertical axis:

()()
()()()
[A + A]
WOW ! WOW
OH-AH_wx'xw_HA-HO
(<<[[[T*T]]]>>)
(:)
)-(
())(()
qpqp

while the following are not:

())(
((B))
11
+-*+-
WOW ! wow
(;)
qppq

Rules of the contest

• Your program or function will receive only printable ASCII characters. You can include or not the empty string, (which is symmetric, of course!) as legal input, which is better for you.

• The ASCII characters that can be considered symmetric with respect to the vertical axes are the following (note the initial space, and the difference between uppercase and lowercase letters):

 !"'+*-.:=AHIMOTUVWXY^_ovwx|

The ASCII characters that can be considered “mirrored” and their corresponding characters are:

()<>[]{}qpbd/\

Note that, since they are mirrored, you can have both () as well as )(, /\ and \/, etc.

All the other ASCII printable characters must be considered asymmetric and without a mirrored corresponding character.

• This is a code-golf challenge: the shorter your program is, measured in bytes, the better, in any programming language.

• Kudos to people that will produce a symmetric program!

Answer 28

Simulate Alpha Decay

Answer 29

Zoom box drawing characters

Here are some sample box drawing characters:

  ╷
 ┌┴┐
╶┤ ├╴
 └┬┘
  ╵

How do we zoom them? Well, we need to triple their size. The result looks like this:

      ╻
      ┃
      ┃
   ┏━━┻━━┓
   ┃     ┃
   ┃     ┃
╺━━┫     ┣━━╸
   ┃     ┃
   ┃     ┃
   ┗━━┳━━┛
      ┃
      ┃
      ╹

As you can see, what happens is this:

• Each box drawing character is replaced by its heavy version (for extra thickness)
• The box drawing characters are extended using the heavy horizontal and heavy vertical characters, resulting in a separation of three between the original characters

You can use any reasonable character I/O format. You will only need to support spaces and the 15 basic box drawing characters, plus newlines if you need them as line separators. You can only require rectangular input, but your output may contain arbitrary whitespace padding, except on the left, so that the characters in the zoomed image are aligned.

This is code-golf, so the shortest solution in bytes that violates no standard loopholes wins, but if you're using UTF-8 encoding then you can score all box drawing characters as 1 each.

Answer 30

Does it have a square? (simple version) code-golf matrix

Given a matrix of 0s and 1s, determine if there are 4 points that are 1 and are the corners of a square.

Here's an example to clarify, with a possible square (in bold):

0 0 0 0 0 0 0 1
0 0 0 1 0 1 0 0
0 0 0 0 1 1 0 0
0 0 0 1 0 1 0 0
1 0 0 0 0 0 0 1
0 1 1 0 0 1 1 1
1 1 1 1 1 0 0 1
0 1 0 0 1 0 1 1
1 1 1 1 0 0 1 0
1 0 0 1 0 1 0 1
0 0 1 0 1 0 1 1
1 0 0 1 1 0 1 1

Another possible square is the following:

0 0 0 0 0 0 0 1
0 0 0 1 0 1 0 0
0 0 0 0 1 1 0 0
0 0 0 1 0 1 0 0
1 0 0 0 0 0 0 1
0 1 1 0 0 1 1 1
1 1 1 1 1 0 0 1
0 1 0 0 1 0 1 1
1 1 1 1 0 0 1 0
1 0 0 1 0 1 0 1
0 0 1 0 1 0 1 1
1 0 0 1 1 0 1 1

There are many squares in this matrix, but the point isn't to count the squares, just to determine if there's a square in it. Since there is a square in it, your solution, given this matrix, must return a truthy value.

Given this matrix, your solution must return a falsy value:

0 0 0 0 0 0
0 1 1 0 0 1
0 1 0 0 1 1
0 1 1 0 1 0

You can see there's no square in there.

Rules

• Since the input is a matrix, it will always be rectangular.
• Probably needless to say, the sides of a square must be equal.
• The corners of a square must all be 1.
• A square must have at least side length 2 to be considered a square, otherwise this challenge would be extremely trivial.
• Standard Loopholes, as usual, are forbidden.

Test cases

This section is under construction.