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

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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

Iterated Prisoner's Trilemma

king-of-the-hill python

Please send me problems or else I'm gonna post this on main.

---

Prisoner's dilemma ... with three choices. Crazy, huh?

Here's our payoff matrix. Player A on the left, B on the top

A,B| C | N | D
---|---|---|---
 C |3,3|4,1|0,5
 N |1,4|2,2|3,2
 D |5,0|2,3|1,1

The payoff matrix is engineered so that it's best for both players to always cooperate, but you can gain (usually) by choosing Neutral or Defection.

Here's some (competing) example bots.

# turns out if you don't actually have to implement __init__(). TIL.

class AllC:
    def round(self, _): return "C"
class AllN:
    def round(self, _): return "N"
class AllD:
    def round(self, _): return "D"
class RandomBot:
    def round(self, _): return random.choice(["C", "N", "D"])

class Grudger:
    def __init__(self):
        self.history = []
    def round(self, last):
        if(last):
            self.history.append(last)
            if(self.history.count("D") > 0):
                return "D"
        return "C"

class TitForTat:
    def round(self, last):
        if(last == "D"):
            return "D"
        return "C"

Your bot is a Python3 class. A new instance is created for every game, and round() is called each round, with your opponent's choice from last round (or None, if it's the first round)

If we get enough entries for the result to be statistically significant, there's a 50 rep bounty for anyone who can beat Tit For Tat.

Specifics

• Round count: [REDACTED]
• Standard loopholes disallowed.
• No messing with anything outside your class.

Answer 2

Posted: Find an array that fits a set of sums

Answer 3

Posted

Find the minimal initial values

Consider a sequence F of positive integers where F(n) = F(n-1) + F(n-2) for n >= 2. The Fibonacci sequence is one example of this type of sequence for F(0) = F(1) = 1, but any two initial values will yield a different sequence. For example F(0) = 3, F(1) = 1 produces these terms.

3, 1, 4, 5, 9, 14, 23, 37, 60, 97, ...

Challenge

The task is to find F(0) and F(1) that minimize F(0) + F(1) given some term of a sequence F(n). Write a function or complete program to complete the task.

Input

Input is a single positive integer, F(n). It may be accepted as a parameter or from standard input. Any reasonable representation is allowed, including direct integer or string representations.

Invalid inputs need not be considered.

Output

The output will be two positive integers, F(0) and F(1). Any reasonable format is acceptable. Here are some examples of reasonable formats.

• Written on separate lines to standard output
• Formatted on standard output as a delimited 2-element list
• Returned as a tuple or 2-element array of integers from a function

Examples

60  -> [3, 1]
37  -> [3, 1]
13  -> [1, 1]
26  -> [2, 2]
4   -> [2, 1]
5   -> [1, 1]
6   -> [2, 2]
7   -> [2, 1]
12  -> [3, 2]
1   -> [1, 1]

Scoring

This is code golf. The score is calculated by bytes of source code.

Answer 4

Implement LogiMuxi code-golf interpreter

The language

LogiMuxi is, as its name suggests, a programming language based on multiplexers.

Built-in gates

• M(A,B,C) (Multiplexer): If A is 0, returns is B, otherwise returns C.
• R() (Random): Returns either 0 or 1 uniformly randomly.
• I() (Input): Reads a bit from STDIN and returns it. Terminates program execution on EOF.
• O(A) (Output): Appends bit A to STDOUT and returns it.

Literals

0, 1 are literals. Literals are expressions, and can be used as values.

Gate calling

G(<arg1>,<arg2>,...,<argx>) calls gate G with the provided arguments in order. Gate calling is an expression.

Conditional loop

G
 <cmd1>
 <cmd2>
 <...>
 <cmdx>

Evaluates G. If G returns 1, the indented commands are executed, and this process repeats again. If G returns 0, the loop is skipped. If there are no indented commands under G, the loop is empty, and, therefore, if G is 0 then nothing happens, while if G is 1 we enter an infinite loop with no way out.

Value assignment

X=G

Assigns X to the result of G. After that, the identifier of the variable can be used as an expression, and it will evaluate to the current value of the variable.

Gate definition

G(<arg1>,<arg2>,...,<argx>)
 <cmd1>
 <cmd2>
 <...>
 <cmdx>

Defines gate G to take arguments <arg1> up to <argx> (actual argument identifiers are specified by the programmer) and return the result of H. The identifiers of the arguments are localized, as well as variables assigned inside the gate. This means that, if I assign variable X to value A outside of G and then there's an X=B command in the definition of G, calling G will not assign X to B. However, inside the gate's scope, X will take the new value B. Assigning the arguments themselves to new values is allowed. Example:

X=0
G(A,B)
 X=1
 O(X)
 :M(R(),A,B)
O(X)

This will output the bits 1 and 0 in order. For reference, G chooses randomly between A and B in this example.

Gate definitons may also be nested, in which case they will be localized too.

Returning happens by prepending a : (colon) to a value (e.g. to return value A, use command :A). This will exit the gate and return the value to the right of it. You can't leave the part to the right of : empty. A gate that doesn't return is invalid.

Additional notes

• Commands are separated by line separators.
• An identifier has to meet these criteria:
  • The first character has to be in ABCDEFGHIJKLMNOPQRSTUVWXYZ_
  • From the second character onward, the identifier must only be composed of characters in ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.
  • It can't be the identifier of any of the built-in gates.
• A variable and a gate may use the same identifier. They can be separated by the way they are invoked. Of course, this is bad practice, but this language is already pretty esoteric. ;-)
• Use of an undefined identifier is invalid.
• A gate is always to be called with parentheses, even if it doesn't take arguments. This includes the built-in gates.
• A gate may only return one output, and it must return one.
• Nested loops or gates are represented with the appropriate number of spaces used as indentation.
• Useless indentation is prohibited.
• Lines may be empty, but their indentation is significant. Empty lines do nothing.
• Calling gates with the wrong number of arguments is invalid.
• If the number of bits sent to STDOUT isn't a multiple of 8, the bits are post-padded with 0s (e.g. if STDOUT is 00010000 11100, it will be converted to 00010000 11100000 before actual printing).
• If 8 bits have been sent to STDOUT, they will be converted to a character and output immediately.
• Any syntax not defined above should be considered undefined.

Reference gates

You may skip this section.

NOT:

NOT(A)
 :M(A,1,0)

AND:

AND(A,B)
 :M(A,0,B)

OR:

OR(A,B)
 :M(A,B,1)

XOR:

XOR(A,B)
 :M(A,B,M(B,1,0))

NAND:

NAND(A,B)
 :M(A,1,M(B,1,0))

NOR:

NOR(A,B)
 :M(A,M(B,1,0),0)

XNOR:

XNOR(A,B)
 :M(A,M(B,1,0),B)

Simplification tips

You may skip this section.

M(A,0,1) → A

M(M(A,1,0),B,C) → M(A,C,B)

M(0,B,C) → B

M(1,B,C) → C

Sample programs

You may skip this section.

Infinite loop, no output:

1

Cat:

1
 O(I())

Hello, World!:

O(0)
O(1)
O(0)
O(0)
O(1)
O(0)
O(0)
O(0)
O(0)
O(1)
O(1)
O(0)
O(0)
O(1)
O(0)
O(1)
O(0)
O(1)
O(1)
O(0)
O(1)
O(1)
O(0)
O(0)
O(0)
O(1)
O(1)
O(0)
O(1)
O(1)
O(0)
O(0)
O(0)
O(1)
O(1)
O(0)
O(1)
O(1)
O(1)
O(1)
O(0)
O(0)
O(1)
O(0)
O(1)
O(1)
O(0)
O(0)
O(0)
O(0)
O(1)
O(0)
O(0)
O(0)
O(0)
O(0)
O(0)
O(1)
O(0)
O(1)
O(0)
O(1)
O(1)
O(1)
O(0)
O(1)
O(1)
O(0)
O(1)
O(1)
O(1)
O(1)
O(0)
O(1)
O(1)
O(1)
O(0)
O(0)
O(1)
O(0)
O(0)
O(1)
O(1)
O(0)
O(1)
O(1)
O(0)
O(0)
O(0)
O(1)
O(1)
O(0)
O(0)
O(1)
O(0)
O(0)
O(0)
O(0)
O(1)
O(0)
O(0)
O(0)
O(0)
O(1)

1-bit half adder:

A=I()
B=I()
O(M(A,0,B))
O(M(A,B,M(B,1,0)))

Challenge rules

• You may assume you'll not receive an invalid program, or a program with input that will make it do invalid actions, so you don't need to check it for validity.
• The program can be either separated by line separators, or given as a list of lines. Acceptable line separators are \n, \r\n and \r (\n denotes character 0x0A, \r denotes character 0x0D).
• Input can be taken in any reasonable form explicitly separated from the program, not necessarily from STDIN. Also, it can either be the actual input, or its bits (e.g. you can take 0100000001000001 instead of @A). It's guaranteed to be finite for this challenge.
• Output can be provided in any reasonable form, either as bits or as text. Also, you don't actually need to output while the program is executing, unlike what the specification above says.
• You may use any four distinct identifiers for the built-in gates M, R, I and O. Identifier rules will apply to your chosen identifiers in this case.
• You may use [] instead of (), and/or tabs instead of spaces in indentation. You must be consistent with these choices.

Answer 5

Sock Drawer Simulator

code-golf random

Socks are often kept in drawers, and when people wear socks they like the left and right socks to match ^{[citation needed]}.

Challenge

Given an array of the number of socks of each color, simulate the process of drawing socks, and output the color of the first pair found. You may assume that:

• Socks are drawn sequentially, randomly and without replacement.
• A pair is found when a sock of a color that has already been drawn is drawn.

Obviously, the precise algorithm doesn't matter as long as the output probability distribution is correct.

Input

A nonempty array of positive integers representing the frequency of each color of sock. For example, [3,1,4,1,5] could represent a drawer with three teal, one aquamarine, four green, one cyan, and five cerulean socks. There will always be at least one possible pair.

Output

A nonnegative integer representing the color (index) of the sock drawn. You may consistently use either one-indexed or zero-indexed arrays.

Answer 6

Survival Game: Alien Hunters (working title)

king-of-the-hill java

Based on Create Your Wolf, but the combat is very different.

---

Somewhere, deep in the heart of the galaxy, lies the planet Oizys. A toroidal planet in the habitable zone of its star, its bountiful land and beautiful oceans make it the perfect planet for your race of aliens to start colonizing as an interstellar civilization.

Unfortunately, a few dozen other alien races are also trying to colonize it, and you can't stand them. So you're going to have to kill them.

Your Alien

Your task is to write an implementation of the net.ramenchef.oizys.Alien class:

package net.ramenchef.oizys;

public class Alien {
    public enum Move {
        // a whole bunch of values; these are described in "the board"
    }

    /**
     * Used by the runner to keep track of the alien's energy.
     */
    double energy = 1.0;

    /**
     * Moves the alien.
     *
     * @param surroundings The alien's surroundings. The first
     *  dimension is North–South, with index 0 being North. The second
     *  dimension is East–West, with index 0 being West.
     * @return A {@code Move} object representing the direction to
     *  move the alien
     */
    public abstract Move move(char[][] surroundings);

    /**
     * Called when the alien is in battle.
     *
     * @param opponents The other aliens on this tile that need to be
     *  fought
     * @return The amount of energy to use in this battle
     */
    public abstract double attack(char[] opponents);
}

100 instances of your class will be spawned in random locations on the board for each trial. Each alien class will be assigned a unique character to represent them on the board.

There are a number of stock alien races that already inhabit Oizys:

• Rocks: they do absolutely nothing and don't pose any sort of threat (i.e., they attack with 0 energy), but for some reason your generals don't know what rocks are, so they appear just like any other alien.
• Random Bears: they act randomly. They move in a random direction (including possibly not moving at all) and attack using a random portion of their energy.

The Board

Oizys is a toroidal planet, so the board will be side-looped on both edges. The width and height of the board will be equal to \$\left\lceil\sqrt s\right\rceil\$, where s is the number of alien species. Each round, your aliens will have the option to move one tile horizontally and/or vertically with the move method. This method takes a 3x3 char[][] representing the alien's surroundings, with a[0][0] being Northwest and a[0][2] being Northeast, and returns a Move enum. The possible Move values are NORTHWEST, NORTH, NORTHEAST, WEST, HOLD, EAST, SOUTHWEST, SOUTH, and SOUTHEAST.

Combat

If two or more aliens attempt to move into the same tile, they will fight. What better opportunity to kill those annoying other aliens! Or maybe get killed yourself, who knows? Each alien starts with 1 energy, and uses it to fight other aliens. When aliens fight, they use the attack method, which takes a char[] representing their opponents and returns a double, to determine how much energy they will use for that battle. The alien that uses the most energy wins, and the others die. In the case of a tie, the winner is determined by coin flip. An alien cannot use more energy than it has or it will die; neither can it use a negative amount of energy.

Scoring

Five trials will be held, with each trial being scored by the portion of the aliens remaining that are your alien. These trials will be held on [1 month after the challenge is posted].

Other Rules

• Standard loopholes are forbidden.
• Aliens attempting to alter field visibility/writability will be met with mysterious SecurityExceptions.
• The order that aliens' methods are called is undefined, though there is a happens-before relationship between calls on successive rounds, as well as between aliens moving and those same aliens attacking each other.

Answer 7

Count smooth numbers

fastest-code number-theory primes combinatorics

Define \$\Psi(x,B)\$ as the number of integers between \$1\$ and \$x\$, whose prime factors are all \$B\$ or less. (These are the \$B\$-smooth numbers.)

For example, there are 34 integers between 1 and 100 that have only 2, 3 and 5 as prime factors. These are:

 1  2  3  4  5  6  8  9 10 12
15 16 18 20 24 25 27 30 32 36
40 45 48 50 54 60 64 72 75 80
81 90 96 100

Therefore, \$\Psi(100,5)=34\$. The next prime is 7, so \$\Psi(100,6)\$ is also 34.

This is a challenge to calculate exact values of \$\Psi\$ as quickly as possible.

Methods

You may not use libraries or built-ins that calculate this function. That being said, I don't know any language that has a built-in for this (not even Mathematica?)

I also can't seem to find any fast algorithms for this problem, except for a basic meet-in-the-middle by Daniel J. Bernstein which might be a good starting point.

Bernstein also describes an approximation method that may or may not be useful.

Input range

You may assume that \$1<B\leq x\leq 10^{100}\$ and \$B<10^6\$.

Scoring

You will be scored on tiers of increasing difficulty.

Each tier has several inputs \$(x,B)\$ such that the \$\Psi(x,B)\$ have similar values, and the \$x\$ values are distributed exponentially. Tiers will start at around \$\Psi(x,B)\approx 10^9\$ and go up to \$\Psi(x,B)\approx 10^{20}\$ or more, depending on how fast the entries get.

The time limit for each tier is 60 CPU seconds per input on average. In other words, if a tier has \$n\$ inputs, you will essentially have \$n\$ CPU minutes to obtain the outputs. You are welcome to submit parallel code but each thread will count towards the time limit.

Your score is the highest tier that your program can solve. If there is a tie, the program that is fastest on the highest tier wins.

For practical reasons, your program will be limited to 15GiB of memory.

Sample tiers

Warm-ups:

3:
  Ψ(10^3, 997) = 1000
  Ψ(10^6, 7)   = 1273
  Ψ(10^9, 5)   = 1530
6:
  Ψ(10^6,  999983) = 1000000
  Ψ(10^9,  59)     = 1060717
  Ψ(10^12, 29)     = 1469549
  Ψ(10^15, 17)     =  919814
  Ψ(10^36, 7)      =  936046

Tiers:

9:
  Ψ(10^9,  999983) =  616220853
  Ψ(10^10, 4567)   =  954965955
  Ψ(10^12, 337)    = 1180049403
  Ψ(10^15, 97)     = 1016358704
  Ψ(10^18, 59)     = 1106651678
  Ψ(10^24, 31)     =  791377032
  Ψ(10^30, 23)     =  812060729
  Ψ(10^48, 17)     = 1435897064
10:
  Ψ(10^11, 11987) = 10016301575
  Ψ(10^12, 1499)  = 10753426440
  Ψ(10^15, 199)   = 12766644440
  Ψ(10^18, 89)    =  9052115006
  Ψ(10^24, 47)    = 11298682134
  Ψ(10^30, 37)    = 14838208717
  Ψ(10^48, 19)    =  7868307089
11:
  Ψ(10^13, 2297) =  84344528150
  Ψ(10^15, 443)  =  96272828440
  Ψ(10^18, 163)  = 107816435926
  Ψ(10^36, 37)   =  94053521936
  Ψ(10^24, 67)   =  81421195505
  Ψ(10^48, 29)   = 151266342065

etc.

I may choose to do the actual scoring on different inputs, including using \$x\$'s that are not powers of 10.

Answer 8

Squish these Numbers

META: I think my wording is not very clear, if you have a suggestion to make it easier to understand, feel free add a commment or edit it directly in to this post.

code-golf math array-manipulation arithmetic statistics

Given a finite sequence of real floating point numbers, map it into the Interval \$[-1,1]\$, such that the order of these numbers is preserved.

Details

• You can choose any mapping you like, it doesn't have to be linear.
• The mapping you choose doesn't have to stem from a function, that means some number \$x\in \mathbb R\$ doesn't have to get mapped to the same number in \$[-1,1]\$, the value it does get mapped to can change depending on the other values in the input list.
• Two equal values in the input list, should remain equal in the output.
• If some value in the input list is strictly smaller than some other value, then the corresponding values in the output should satisfy the same relation, in theory. In practice it might happend that two different numbers will get mapped to the same output due to floating point arithmetic issues, which is fine - as long as it would work with an arbitrary precision.
• You can assume the input sequence contains at least two distinct entries.

Examples

Following example finds a linear map that maps the least entry to \$-1\$ and the greatest entry to \$1\$. Note how this map depends on the sequence.

$$ (x_1,x_2,\ldots,x_n) \mapsto \left( \frac{x_i - \min_k x_k}{\max_k x_k - \min_k x_k} \right)_{i=1}^n $$

Following example is a fixed function that always behave the same. Because it is monotonic and strictly increasing, it satisfies all conditions. $$ (x_i)_{i=1}^n \mapsto \left(\frac{\arctan(x_i)}{\pi} \right)_{i=1}^n$$

Thanks @PeterTaylor for following example. Here \$\operatorname{sort}(x)\$ sorts the input sequence in ascending order and \$\operatorname{indexof}(u,v)\$ returns the index of the first occurence of \$v\$ in the sequence \$u\$.

$$(x_i)_{i=1}^n \mapsto \left( \frac{1}{n} \operatorname{indexof}(\operatorname{sort}(x),x_i)\right)_{i=1}^n$$

Answer 9

Shortest JsFuck code for a number

JsFuck is a language using only []()!+ to run and express anything in JavaScript. Below is a simplified model of JavaScript to express numbers:

• Types
  1. Number
  2. String
  3. Boolean (true)
  4. Array
• Functions
  • IEEEdouble(x):
    • Let \$u\$ is the number in \$\{a\cdot 2^{b}|-2^{53}<a<2^{53}, b>-1075, a,b\in \mathbb Z\}\$ nearest to x, maximizing \$b\$ on tie
    • If \$|u|<2^{1024}\$, return \$u\$
  • toNumber(x):
    • If x is a Number, return x;
    • If x is a Boolean, return 1;
    • If x is an Array [y], return toNumber(y);
    • If x is an Array [], return 0;
    • Otherwise, x is a String. In this case,
    • If x matches /^([\+\-]?(?:\d*\.?\d+|\d+\.))(?:e([\+\-]?\d+)?$/, let \$v=\text{＄1}\times 10^\text{＄2}\$ ($2 is zero if not present)
    • Return IEEEdouble(\$v\$)
  • toString(x):
    • If x is a String, return x;
    • If x is a Boolean, return 'true';
    • If x is an Array [y], return toString(y);
    • If x is an Array [], return '';
    • Otherwise, x is a Number. In this case,
    • Find \$p, q\in \mathbb Z\$ such that IEEEdouble(\$p\times 10^q\$)=x, maximizing \$q\$(there may be multiple \$p\$ satisfying the restriction, in which case choosing which one is unknown);
    • Let \$y=p\times 10^q\$;
    • If \$y=0\$ or \$10^{-6}\leq|y|<10^{21}\$, write it normally without scientific notation mapping the RegEx /^([1-9]\d*|0)(\.\d*[1-9])?$/;
    • Otherwise, write it in scientific notation mapping the RegEx /^[1-9](\.\d*[1-9])?e[\+\-][1-9]\d*$/
  • x+y
    • If either x or y is a String or an Array, return toString(x) concatted with toString(y);
    • Otherwise, return IEEEdouble(the sum of toNumber(x) and toNumber(y))
  • +x
    • Return toNumber(x)
  • [] and [x]
    • Return an Array.
  • x[y]
    • If x is a String, return the y^th character(0-index) in x
  • !![] and !+[]
    • Return a Boolean

A valid JsFuck code is always parenthesis balanced without two symbols + together. Expression in parenthesis is calculated before the one out. On the same layer operations go from left to right.

You are required to output the shortest JsFuck code that generates a given IEEE double (A possible output of IEEEdouble). Shortest generator wins.

It's fine if your generator runs slow, but beware of potential infinite loop if you eval.

Samples

1     -> +!![]
2     -> !![]+!![]
10    -> +[+!+[]+[+[]]]
1e10  -> +(+!![]+(!![]+[])[!![]+!![]+!![]]+(+!![])+(+[]))
0.1   -> +((+(+!![]+[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+!![])+(+[]))+[])[+!![]]+(+!![]))
1e-10 -> +((+(+!![]+[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+!![])+(+[]))+[])[+!![]]+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+!![]))
5e-324-> +(!![]+!![]+!![]+(!![]+[])[!![]+!![]+!![]]+(+((+(+!![]+[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+!![])+(+[]))+[])[+!![]]+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+!![]))+[])[!![]+!![]]+(!![]+!![]+!![])+(!![]+!![])+(!![]+!![]+!![]+!![]))
9999999999
      -> +(+!![]+(!![]+[])[!![]+!![]+!![]]+(+!![])+(+[]))+(+((+((+(+!![]+[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+!![])+(+[]))+[])[+!![]]+(+[])+(+[])+(+[])+(+[])+(+[])+(+[])+(+!![]))+[])[!![]+!![]]+(+!![])))

SN: Another way to ask is requiring to be testable and shouldn't be longer than a chosen generator

Answer 10

Is it shifted?

code-golf decision-problem keyboard

Consider a standard US-International QWERTY keyboard, without a numeric keypad, and Caps Lock mysteriously missing.

< insert image >

The goal is to write two programs or functions that take no input, and each give a distinct output through any default output method: Shift and No shift respectively. The program that outputs No shift has to be written without use of the ⇧ Shift key. The program that outputs Shift has to be written while holding the ⇧ Shift key throughout. Both programs have to be written using the exact same sequence of keypresses. A valid entry would be a1b2 + A!B@, if they output No shift and Shift respectively.

The symbols allowed for the "No-shift" program are as follows:

`1234567890-=
qwertyuiop[]\
asdfghjkl;'
zxcvbnm,./
<space> <newline> <tab> 

The symbols allowed for the "Shift" program are as follows:

~!@#$%^&*()_+
QWERTYUIOP{}|
ASDFGHJKL:"
ZXCVBNM<>?
<space> <newline>

Note that Tab ↹ is missing, since Shift+Tab ↹ does not produce a \t tab symbol in most editors.

Sandbox note

I think using case-sensitive output makes the challenge more challenging, but it might become too challenging. What are your thoughts?

Answer 11

Touch-typing distance

Tags: code-golf, string

Related: Levenshtein distance

---

There are many different string metrics, a simple one is the Levenshtein distance given by \$\texttt{ld}_{a,b}(|a|,|b|)\$:

$$ \texttt{ld}_{a,b}(i,j) = \begin{cases} \max(i,j), & \text{if $i = 0$ or $j = 0$} \\ \\ \min \begin{cases} \texttt{ld}_{a,b}(i-1,j) + c_\text{deletion} \\ \texttt{ld}_{a,b}(i,j-1) + c_\text{insertion} \\ \texttt{ld}_{a,b}(i-1,j-1) + w(a_i, b_j) \end{cases}, & \text{otherwise} \end{cases} $$

The avid reader may have noticed that there are missing pieces in the above definition, it makes use of a weight function \$w\$ which was never defined and the costs \$c_\text{deletion}\$ as well as \$c_\text{insertion}\$.

The Levenshtein distance uses an indicator function which evaluates to \$1\$ if the two characters are not equal and \$0\$ otherwise and costs \$1\$ for deletion and insertion. This does not take into account that a mistake of typing u instead of w should cost more than mistakenly typing an e. Let's try to fix this!

Challenge

For this challenge we'll assume a QWERTY keyboard and only take lower-case letters into account. We will use the usual letter-to-finger assignment (left-most finger to right-most) ["qaz","wsx","edc","rtfgvb","yuhjnm","ik","ol","p"]:

Left Hand

• pinky: qaz
• ring finger: wsx
• middle finger: edc
• index finger: rtfgvb

Right Hand

• index finger: yuhjnm
• middle finger: ik
• ring finger: ol
• pinky: p

---

Now, to define a new string metric we will use the following definitions in the above generalized Levenshtein distance: Set \$c_\text{deletion} = c_\text{insertion} = 8\$ and for \$w(a_i,b_j)\$ we will use the distance of the two characters plus \$1\$ according to the above assignments (unless they are equal, then we'll use \$0\$). Here are a few examples:

'q' 'q' -> 0
'q' 'a' -> 1
'q' 'w' -> 2
'l' 'g' -> 4
'p' 'a' -> 8

Rules

Input will be two strings \$a\$ and \$b\$ which

• are non-empty
• only contain lower-case letters (ie. match ^[a-z]+$)

Output will be the "touch-typing distance" as defined above.

Test cases

"todo" "todo" → 0

Answer 12

Shift right by half a bit code-golf math number arithmetic

The challenge is to implement a program or function ^{(subsequently referred to as "program")} that takes a nonnegative integer \$n\$ as input and returns \$n\over\sqrt{2}\$ (the input divided by the square root of two) as output, rounded to a nonnegative integer.

You may take your input and output in any reasonable format; for example stdin/stdout, files, or arguments/return values would all be acceptable.

You are required to use, at minimum, the largest fixed-size integer type offered by your language, and if an unsigned variant of this is available, you must use it. If your language has no built-in integer type (e.g. JavaScript) you are allowed to use its default numerical type (e.g. floating point); for languages with no concept of a number (e.g. regex), input and output can be e.g. the length of a string.

It is not required to reject negative integers; a submission that returns correct answers for negative inputs is allowed, but not required. Undefined behavior with negative inputs is allowed.

You are allowed and encouraged to use arbitrary-precision integer types if you so desire, but the type must either be a built-in, part of a standard library, or implemented from scratch in your program.

Despite what the title might imply, you may use any rounding algorithm you want (floor, ceiling, nearest half up, nearest half even, arbitrary, or even random), as long as the difference between the integer returned value and the theoretical exact (irrational) value is always less than \$1\$ for all inputs that fit in your chosen integer type. All inputs up to the maximum representable value must return a correct output.

In a way, the job of this program is to calculate the irrational number \$\sqrt{2}\$ to the requested precision, presenting it in the form of an integer. This is why solutions using arbitrary-precision types are encouraged, but not required.

This is a code-golf challenge. Standard loopholes are denied. The program with the least number of bytes wins. If there's a tie, the choice of accepted answer will be at my discretion. That said, this challenge is not only about which answer wins; it's also about seeing how concisely the challenge can be solved in each language, and seeing how each language "prefers" to handle rounding. And for those submissions that choose to use arbitrary precision, it's about seeing how concisely this can be done in the language.

Meta

The primary reason for the question is that I want to post my ECMAScript regex solving it. Currently all I have is an 849 byte _{^{(very heavily golfed down from an initial 1159 bytes)}} ECMAScript + molecular lookahead regex, i.e. not purely ECMAScript-compatible and only works on my regex engine, so this question can stew in the Sandbox for a while until I port the regex to pure ECMAScript at some point, and/or put the regex engine on TIO.

That said, I am genuinely interested in what submissions PPCGers will come up with for this challenge (including in the languages more frequently seen in PPCG posts), and will treat the hosting of it seriously. Also there's the chance that someone will attempt solving it in a more powerful regex flavor, and I'd be fascinated to see if this could be done in significantly less length than ECMA (I actually doubt it can). Or somebody could come up with a crazy solution for it in some other language that has limits imposed which make it hard to do.

And if somebody could think of a way to solve it in ECMA in fewer bytes than I have (or even just golf down my regex), that would be fascinating (or thrilling) as well.

I'd be interested in putting up a bounty for the regex aspects of this question, and would appreciate any suggestions people would have as to how to do this and how much the bounty should be.

Answer 13

Irregular English Verbs

text-processing string code-golf compression kolmogorov-complexity

Given the infinitive of an irregular English verb, output its simple past and its past participle.

Rules

• The input and output can be given in any convenient format.
• No need to handle verbs not in the given list.
• Either a full program or a function are acceptable. If a function, you can return the output rather than printing it.
• If possible, please include a link to an online testing environment so other people can try out your code!
• Standard loopholes are forbidden.
• This is code-golf so all usual golfing rules apply, and the shortest code (in bytes) wins.

Example

fall    --> fell; fallen
beat    --> beat; beaten or beat
bereave --> bereaved or bereft; bereaved or bereft
shall   --> should;(no participle)

List of Irregular Verbs

Infinitive;Simple Past;Past Participle
alight;alighted or alit;alighted or alit
arise;arose;arisen
awake;awoke or awaked;awoken or awaked
be;was or were;been
bear;bore;borne or born
beat;beat;beaten or beat
become;became;become
beget;begot;begotten
begin;began;begun
bend;bent;bent
bereave;bereaved or bereft;bereaved or bereft
beseech;besought or beseeched;besought or beseeched
bet;bet or betted;bet or betted
bid;bade or bid;bidden or bid or bade
bide;bade or bided;bided
bind;bound;bound
bite;bit;bitten
bleed;bled;bled
bless;blessed or blest;blessed or blest
blow;blew;blown
break;broke;broken
breed;bred;bred
bring;brought;brought
broadcast;broadcast or broadcasted;broadcast or broadcasted
build;built;built
burn;burnt or burned;burnt or burned
burst;burst;burst
bust;bust or busted;bust or busted
buy;bought;bought
can;could;(no participle)
cast;cast;cast
catch;caught;caught
choose;chose;chosen
cleave;cleft or cleaved or clove;cleft or cleaved or cloven
cling;clung;clung
clothe;clothed or clad;clothed or clad
come;came;come
cost;cost;cost
creep;crept;crept
crow;crowed;crew or crowed
cut;cut;cut
deal;dealt;dealt
dig;dug;dug
do;did;done
draw;drew;drawn
dream;dreamt or dreamed;dreamt or dreamed
drink;drank;drunk
drive;drove;driven
dwell;dwelt or dwelled;dwelt or dwelled
eat;ate;eaten
fall;fell;fallen
feed;fed;fed
feel;felt;felt
fight;fought;fought
find;found;found
flee;fled;fled
fling;flung;flung
fly;flew;flown
forbid;forbad or forbade;forbid or forbidden
forecast;forecast or forecasted;forecast or forecasted
forget;forgot;forgotten
forsake;forsook;forsaken
freeze;froze;frozen
geld;gelded or gelt;gelded or gelt
get;got;got or gotten
gild;gilded or gilt;gilded or gilt
give;gave;given
gnaw;gnawed;gnawed or gnawn
go;went;gone
grind;ground;ground
grip;gripped or gript;gripped or gript
grow;grew;grown
hang;hung;hung
have;had;had
hear;heard;heard
heave;heaved or hove;heaved or hove
hew;hewed;hewed or hewn
hide;hid;hidden or hid
hit;hit;hit
hold;held;held
hurt;hurt;hurt
keep;kept;kept
kneel;knelt or kneeled;knelt or kneeled
knit;knitted or knit;knitted or knit
know;knew;known
lay;laid;laid
lead;led;led
lean;leant or leaned;leant or leaned
leap;leapt or leaped;leapt or leaped
learn;learnt or learned;learnt or learned
leave;left;left
lend;lent;lent
let;let;let
lie;lay;lain
light;lit or lighted;lit or lighted
lose;lost;lost
make;made;made
may;might;(no participle)
mean;meant;meant
meet;met;met
melt;melted;molten or melted
mow;mowed;mown or mowed
pay;paid;paid
pen;pent or penned;pent or penned
plead;pled or pleaded;pled or pleaded
prove;proved;proven or proved
put;put;put
quit;quit or quitted;quit or quitted
read;read;read
rid;rid or ridded;rid or ridded
ride;rode;ridden
ring;rang;rung
rise;rose;risen
run;ran;run
saw;sawed;sawn or sawed
say;said;said
see;saw;seen
seek;sought;sought
sell;sold;sold
send;sent;sent
set;set;set
sew;sewed;sewn or sewed
shake;shook;shaken
shall;should;(no participle)
shear;sheared;shorn or sheared
shed;shed;shed
shine;shone;shone
shit;shit or shitted or shat;shit or shitted or shat
shoe;shod or shoed;shod or shoed
shoot;shot;shot
show;showed;shown or showed
shred;shred or shredded;shred or shredded
shrink;shrank or shrunk;shrunk
shut;shut;shut
sing;sang;sung
sink;sank;sunk
sit;sat;sat
slay;slew;slain
sleep;slept;slept
slide;slid;slid
sling;slung;slung
slink;slunk;slunk
slit;slit;slit
smell;smelt or smelled;smelt or smelled
smite;smote;smitten
sow;sowed;sown or sowed
speak;spoke;spoken
speed;sped or speeded;sped or speeded
spell;spelt or spelled;spelt or spelled
spend;spent;spent
spill;spilt or spilled;spilt or spilled
spin;spun;spun
spit;spat;spat
split;split;split
spoil;spoilt or spoiled;spoilt or spoiled
spread;spread;spread
spring;sprang or sprung;sprung
stand;stood;stood
steal;stole;stolen
stick;stuck;stuck
sting;stung;stung
stink;stank or stunk;stunk
stride;strode;stridden
strike;struck;struck
string;strung;strung
strive;strove;striven
swear;swore;sworn
sweat;sweat or sweated;sweat or sweated
sweep;swept;swept
swell;swelled;swollen or swelled
swim;swam;swum
swing;swung;swung
take;took;taken
teach;taught;taught
tear;tore;torn
telecast;telecast or telecasted;telecast or telecasted
tell;told;told
think;thought;thought
throw;threw;thrown
thrust;thrust;thrust
tread;trod;trodden
understand;understood;understood
wake;woke or waked;woken or waked
wear;wore;worn
weave;wove;woven
wed;wed or wedded;wed or wedded
weep;wept;wept
wet;wet or wetted;wet or wetted
win;won;won
wind;wound;wound
wring;wrung;wrung
write;wrote;written

Answer 14

Generate a 3D spiral

Inspired by this chat message

The spiral used in The Path Of The Wildebeest is a contiguous mapping of the positive integers to lattice points in 2D. Your task is to generalize this to 3D.

Specifically, create a function \$f\$ from \$\mathbb Z^+\$ to \$ \mathbb Z^3\$ with the following properties:

• \$f\$ is a bijection (All points are eventually reached).
• \$f(1) = (0,0,0)\$ (The spiral starts at the origin).
• \$ |f(n+1) - f(n)| = 1\$ (The spiral is contiguous).
• The Chebyshev distance from the origin \$ |f(n)|_\infty \$ is a nondecreasing function (\$f\$ fills all points in each concentric cubical shell \$k\$ before moving to shell \$k+1\$).

One possible \$f\$ is given by this Python implementation, but any \$f\$ that satisfies the above properties is allowed. Please describe the function your answer generates.

Because all your computer's memory is taken up by the wildebeest simulation you're running, typing is very slow, so your code must be as short as possible.

I/O

As is standard with sequence questions, either 1-indexing or 0-indexing is allowed. Any of these I/O formats are acceptable:

• Receive \$n\$ as input and output the \$n\$th point in the sequence
• Receive \$n\$ as input and output the first \$n\$ points
• Take no input and output the sequence infinitely.

Answer 15

Countries by Area

Answer 16

Least efficient field order

Background:

In C and other languages, a struct is a data type composed of fields of other data types. These fields may be different sizes (in bytes) and may have different alignment requirements (e.g. an int field may need to be on a 4-byte boundary).

Padding is added to a struct to keep all of its fields aligned, and to keep its size a multiple of each field's alignment.

For example:

struct test {
    char  a; // 1-byte, 1-byte aligned
    short b; // 2-byte, 2-byte aligned
    int   c; // 4-byte, 4-byte aligned
}

In this struct, there will be 1 byte of padding after a (to keep b on a 2-byte boundary), no padding after b (as c is already on a 4-byte boundary) and no padding after c (as the size is already a multiple of 2 and 4 bytes), so the total size of the struct is 8 bytes (1 + 2 + 4 + 2). However, if we rearrange the order of the fields, the struct size can be bigger.

struct test_2 {
    char  d; // 1-byte, 1-byte aligned
    int   e; // 4-byte, 4-byte aligned
    short f; // 2-byte, 2-byte aligned
}

In this struct, there will be 3 bytes of padding after d (to keep e on a 4-byte boundary) and there will be 2 bytes of padding after f (to keep the size a multiple of 2 and 4 bytes), so the total size of this struct is 12 bytes (1 + 4 + 2 + 3 + 2).

Challenge:

Given a list of pairs of positive integers (each pair representing the size and alignment of a field), return the same pairs in an order such that a struct with fields in that order would require the most padding, i.e. be the least space-efficient.

Givens:

• A field's size will always be greater than or equal to its alignment. (e.g. (4, 8) is not a valid input pair)

• A field's size will always be a multiple of its alignment. (i.e. (12, 5) is not a valid input pair)

Test cases: (other outputs that give the same total size are valid as well)

[(1, 1), (1, 1), (4, 4)] -> [(1, 1), (4, 4), (1, 1)] # size 12
[(12, 4), (1, 1), (2, 2), (8, 8)] -> [(12, 4), (8, 8), (1, 1), (2, 2)] # size 32
[(7, 7), (5, 1), (2, 2)] -> [(7, 7), (2, 2), (5, 1)] # size 28
[(6, 6), (6, 3), (4, 2), (2, 2)] -> [(6, 3), (4, 2), (6, 6), (2, 2)] # size 24
[(1, 1)] -> [(1, 1)] # size 1

Test case checker online!

Answer 17

The Minigame Challenge

cops-and-robbers code-golf

The idea of this CnR is fairly simple: The Cops must create a simple minigame (explained in more detail below), with a definite goal. That goal may or may not be achievable. The Robbers must then either complete the minigame, or prove its goal is not achievable.

Rules

The Minigame

The Cops will create a suitably simple minigame with a definite goal.

Acceptable minigame examples are functions that take some input and return some output, with the goal being to either achieve a specific output, or make the program terminate or error.

Minigames considered complex (and thus unnacceptable) would be programs/functions that will never terminate in up to 60s (using TIO as a benchmark here), or that simulate complex games (such as blackjack, chess, etc).

Note: I'll try to expand further on what kinds of minigames are acceptable or not. Suggestions are appreciated.

Cops:

The Cops must provide one of the following:

• A solution for your minigame that achieves the goal, or
• A proof that the goal for your minigame is not achievable.

at least 7 days (168h) after the answer was posted for their answer to be considered safe.

If your minigame's goal is achievable, it must always be achievable, and it must not contain "insider information", such as a fixed seed for a pRNG, or pregenerated primes as factors of a number to be factored.

Robbers:

To crack an (unsafe) answer, the robber must provide either a solution to the minigame that achieves the stated goal, or a proof that the goal is not achievable.

Scoring:

Cops will be scored based on standard code-golf rules, with the fewest number of bytes in an answer being better. Cracked answers will always have a score of \$\infty\$.

Robbers are scored according to the number of answers they've cracked.

Standard loopholes are, as usual, forbidden.

Challenge is still under construction

This is the first CnR I've ever come up with. Suggestions and observations are always appreciated.

Answer 18

Challenge

Create a function takes in two 2-dimensional arrays of Characters (or Strings if the programming language does not have characters as a datatype) as inputs: a and b.

Your task is to determine if b contains a. If this is so, return true. Otherwise, return false.

Sample Test Cases

a:

123
456
789

b:

123
456
789

should return true.

a:

code
golf

b:

thisis
code!!
golf!!
ohyeah

should return true.

a:

abcd
efgh
ijkl

b:

abcdef
ghijkl
mnopqr

should return false.

Least bytes wins.

Answer 19

Finding Points in Convex Hulls

Convex hulls are notoriously hard to deal with, so today's challenge will deal with a relatively simple premise: given a convex hull defined by a set of points, and an additional point, find whether the additional point lies in the hull.

Now, for some definitions

1. The convex hull of a finite set X, a subset of R^n, is the set of convex combinations of points of $X$.
2. A convex combination of points x1,x2,...,xn is a point of the form a1x1+a2x2+...+anxn such that all ai>=0 and the sum of all of the ai is 1.

Input/Output

The input is rather flexible, as long as it contains the appropriate information to express the convex hull and additional point.

An example of a valid input format to express the convex hull represented by (0,1,2),(4,3,2),(8,8,8) and the point (5,5,5) is

([(0,1,2),(4,3,2),(8,8,8)],(5,5,5))

The output is a truthy/falsy value, depending on whether the point is contained in the hull.

Remarks

There are a lot of packages and libraries that deal with convex hulls, such as scipy.spatial. Such libraries/packages are explicitly banned. Libraries that facilitate matrix computations, such as numpy, are permitted.

The winning criterion is code-golf.

There is no limit on the number of dimensions the points can lie in, as long as they all lie in the same number of dimensions.

Test Cases

I will be using the following tio link for testing the validity of solutions.

Some smaller test cases:

([(1,1)],(1,1)) - True
([(1,1)],(1,2)) - False
([(1,1,1),(3,3,1)],(2,3,1)) - False
([(1,1,1),(3,3,1)],(2,2,1)) - True
([(0,0),(3,3),(0,6)],(2,4)) - True
([(0,0),(3,3),(0,6)],(1,1)) - True
([(0,0),(3,3),(0,5)],(2,4)) - False

Questions for Sandbox

Is code golf the best criteria for this? That might encourage brute force searches on every combination of points... any suggestions?

Answer 20

This is a post to pre-test for a duplicate question before I spend the time to finish the full post and add test cases.

So, have we ever had a question for a "snake rotation" of a matrix:

    +--------------+
      1  2  3  4  5|
    +------------  |
    |10  9  8  7  6|
    |  +-----------+
    |11 12 13 14 15
    +--------------+


    +--------------+
-->  13 14 15  1  2|
    +------------  |
    | 7  6  5  4  3|
    |  +-----------+
    | 8  9 10 11 12  -->
    +--------------+

The ascii walls are there only for clarity. Actual input/output would be normal matrices

Answer 21

WordArt reader

I've decided to leave this very open ended, so that I can write it based on community input. There are a lot of questions in the bottom. All feedback is appreciated, even minor suggestions/comments. :)

image-processing,classification,code-challenge.

---

Did you know WordArt is still a thing in MS Word? Let's parse it!

^{(I'll remove the Swag format)}

The challenge will contain a test battery with X jpg.files each with a word or sentence shown in WordArt. Your task is to parse as many as you can. The winner will be the submission that correctly parses the most images, with date stamp being the tie breaker.

---

Sandboxing:

• Good idea or not?
• Should there be many different styles, or should I stick to one? Colors? Shade/mirroring?
• How many test cases?
• Is jpg the best format (it was used in the Upgoat/Downgoat challenge)
• Should I have a more refined scoring mechanism? It's hard to mix two quantities into one score.
• Should I stick to just letters / alphanumeric / all printable ASCII / multiple lines? Long sentences or single words?
• Orientation? Waves? Circular?
• Resolution?
• Builtin functions?
• Should I require a complete match of images, or character by character?

Answer 22

How many right triangles can you find?

code-golf math

---

Challenge

You will be given an input represented by x, which is a string containing at least 3 characters. It will consist only of the standard numeric characters, 0 through 9. Your job is to find and output how many right triangles can be formed with the given numbers.

Rules

• Numbers must be kept in the order they were given in. No mixing them up!

• The numbers for each right triangle must be consecutive.

• The order of numbers has to be a first, b second, and c third, and must satisfy the formula a² + b² = c². a can be greater than or less than b, as long as it satisfies the formula.

• Decimal points may be added between any numbers.

• Decimals require one or more numbers to be placed before them, e.g. .5 cannot be used as a number but 0.5 and 12.5 can.

• Decimals with at least 4 digits after the decimal point truncated to the third digit, e.g. 1.2345 would truncated to 1.234 and 1.9999 would be truncated to 1.999.

• Numbers can be used more than once in 2 or more different triangles, but cannot be used multiple times in the same triangle.

• Multiple representations of the same value can count multiple times.

• Repeating zeros are allowed, e.g. 000.5 counts as a number.

• All possible combinations must be taken into account for your program to be valid.

Example Inputs and Outputs

Input: 345
Output: 1
This can be split into 3, 4, and 5, which, of course, form a right triangle.

Input: 534
Output: 0
While this does include the necessary numbers to form a right triangle, they are not in the correct order. It has to follow the formula a² + b² = c², but in this case it follows c² = a² + b². The order of numbers cannot be changed from the original input, so in this case no right triangles can be formed.

Input: 3415
Output: 0
This does contain a 3, 4, and a 5, which can form a right triangle, but they are not consecutive; there is a 1 splitting the 5 from the 3 and 4.

Input: 5567507
Output: 1
Because decimals can be added anywhere, it can be changed to 55.67.507, which allows splitting it into 5, 5.6, and 7.507 to form a right triangle. Remember that decimals are truncated to the third digit after the decimal point, which is how we get 7.507.

Input: 345567507
Output: 2
The first right triangle is formed by 3, 4, and 5. The second one is formed by 5567507 (read the previous example for explanation). Numbers can be used more than once, so the first 5 was used in the first and second triangles.

Input: 51125
Output: 0
Because of rule 5, you cannot use .5, 1, and 1.25. An integer is required before .5 for it to work.

Input: 051125
Output: 0
Unlike the previous example, there is a number before the first 5, so it is now legal to use 0.5, 1, and 1.25.

Input: 121418439
Output: 2
The numbers 12 and 14 would form a right triangle where side c has a length of approximately 18.43908891458577462000. Because long decimals are truncated to the third digit after the decimal point, we would be left with 18.439. This fits in with the original input, 121418439. Additionally, 1.2, 1.4, and 1.843 counts as a separate combination, thus giving us our second right triangle.

Input: 10011005
Output: 8
Numbers count separately if they're represented in different ways, so this allows for (1, 00, 1), (1.0, 0, 1), (1, 0, 01), (1, 0.01, 1), (1, 0.01, 1.0), (1, 0.01, 1.00), (1.0, 0.1, 1.005), and (1, 00.1, 1.005).

---

This is code golf, so shortest answer in bytes wins. Good luck!

Answer 23

\$n\$-Chess KotH king-of-the-hillgridchessboard-game

Introduction

Inspired by the challenge N-movers: How much of the infinite board can I reach?, I came up with an idea of applying the \$n\$-mover rules in chess.

\$n\$-Chess™ is a board game played on a 8x8 grid like the original chess. However, the pieces are very different from chess - they are named \$n\$-movers (\$n\$ can be any natural number) and can only move by the rules set on them (see Rules: Pieces).

Rules

Pieces

In \$n\$-chess, a piece is called an \$n\$-mover, where \$n\$ denotes its possible movements. Specifically:

1. The \$n\$-mover can only move one step of Euclidean distance \$\sqrt n\$ each time, i.e. for a move with \$x\$ units horizontal and \$y\$ units vertical, \$x\$ and \$y\$ must fulfill the equation \$x^2+y^2=n\$ in order to be valid.
   • For example, a 5-mover can only move 1 unit in one direction and 2 units in the another at the same time; while a 25-mover can move 5 units in either direction, or 3 units in one direction and 4 units in the another at the same time.
2. A piece can have at most 2 rules set at the same time. For a piece that can act as either an \$m\$-mover or an \$n\$-mover, we can call it an \$(m,n)\$-mover. An \$(m,n)\$-mover is allowed to move one step of Euclidean distance of either \$\sqrt m\$ or \$\sqrt n\$ or \$\sqrt{m+n}\$.
   • It is allowed to have \$m=n\$.
   • Only pieces that has captured other pieces can have multiple rules (See Rules: Capture).
3. If more than 2 rules are set on a piece, only 2 rules can be reserved. You can choose which 2 rules to reserve.

Board

The chess is played on a 8x8 board. The initial setup is as follows:

Capture

1. If a piece lands on a grid that an opponent piece has occupied (capture), that opponent piece shall be moved away from the board.
2. After that, the piece will be granted rules from the captured opponent piece. As stated in Piece, if there are more than 2 rules in total, only 2 shall be reserved.

Playing

1. In a turn, White and Black play a move in turn. White always moves first.
2. Only one piece can be move per turn.
3. You cannot move a piece in the way that is not allowed by the rules set on it, beyond the boundaries of the board, or onto a grid already occupied by your other pieces.
4. You cannot move your last piece in the way that after moving it it can be captured instantly.

Victory Condition

The game ends with either player winning if:

1. The last piece of the opponent is being checkmated, i.e. no possible moves that can save this last piece from being captured; or
2. The opponent resigns and loses. (In this challenge, no resignation will be allowed)

The game ends with a draw if :

3. No checkmate is possible for both sides;
4. Either player has no more possible moves, but is not in checkmate;
5. There is no capture in 50 moves; or
6. The identical board arrangement has appeared 3 times with the same player to move.

Implementation

A player bot is a class that implements a function nextMove(). This function receives 3 arguments and output an array of 6 integers:

function nextMove(
    color: int,                    // Your color: 0 = white, 1 = black
    board: int[8][8][3],           // Current board:
                                   //  First index: x-coordinate
                                   //  Second index: y-coordinate
                                   //  The third layer will be as follows - 
                                   //   [0]: the color of the grid
                                   //       (-1: Not occupied; 0: white; 1: black)
                                   //   [1]: rule 1 (0 if not exists)
                                   //   [2]: rule 2 (0 if not exists)
    moves: int[][10]               // Previous moves:
                                   //  First index: move number (0-indexed)
                                   //  The second layer will be as follows - 
                                   //   [0]: the color of the player
                                   //   [1]: is this a capture (0: no, 1: yes)
                                   //   [2]: source x-coordinate
                                   //   [3]: source y-coordinate
                                   //   [4]: source rule 1
                                   //   [5]: source rule 2 (0 if not exists)
                                   //   [6]: target x-coordinate
                                   //   [7]: target y-coordinate
                                   //   [8]: target rule 1
                                   //   [9]: target rule 2 (0 if not exists)
): int[6]                          // Return value: as follows:
                                   //  [0]: source x-coordinate
                                   //  [1]: source y-coordinate
                                   //  [2]: target x-coordinate
                                   //  [3]: target y-coordinate
                                   //  [4]: target rule 1
                                   //  [5]: target rule 2 (0 if not exists)

• Rule 1 and Rule 2 denotes the 2 rules a piece has.
• Source rule entries are used to denote which rules a piece has, while target rule entries are used to denote which rules are decide to keep.

You may use JavaScript, pseudo-codes, or any languages similar to JavaScript, but using JavaScript is strongly encouraged, because all submissions will be translated to JavaScript before using for competition, and the test drive only supports JavaScript.

Restriction

1. Standard loopholes are forbidden by default.
2. You cannot by any means read or modify other bots. You can only use data within the class and inputs passed to nextMove() function.
3. You may define other variables inside your class if needed.
4. You may use a random number generator.
5. Your bot, specifically the nextMove() function, must return value in 10 second per move. Timeout leads to disqualification.

Procedure

Round-robin will be used to determine the opponents, i.e. all bots will face each of the other bots twice, one as black and one as white. For each game, a win gets 2 points, a lose gets 0 points, and a draw gets 1 points.

The bot will the highest points wins, and if there are any ties, they will be broken by:

1. Number of victories;
2. Average time to checkmate opponent (shorter is better); and
3. Drawing lots. (Hopefully this step is not necessary)

TODO

• Add a sample implementation.

Answer 24

Multi-Digit × Single-Digit Checker code-golf arithmetic

Introduction

The story below is fictional, don't worry.

Times table hard. More curriculum. Class advance. Son behind. Horror. Help.

ahem Pardon me.

So... I've got a big problem. The times table is huge, and all the mnemonic rules we've taught our son haven't make him fully memorize it yet. However, his class must advance to the next chapter, long multiplication. As a result, he is prone to making many mistakes while multiplying numbers.

See, they're already making the students multiply a multi-digit number by a single-digit number. My son often forgets to carry digits over and, of course, his times table. The good thing is that he never misses digits!

The situation is awful. Help me before they start with two multi-digit numbers!

---

Challenge

Your challenge is to write a program that takes a multiplier, a multiplicand and a product, and analyzes the product for any of the following mistakes. Here's how:

• If a digit is the correct ones digit of the product of the multiplicand times the digit of the multiplier he's currently multiplying, but a non-zero carryover was supposed to be added to it, then this digit has a carryover error.
• If a digit is otherwise wrong, there's a times table error around it (we can't be sure if the ones digit was wrong or a carryover digit was wrong), so it has a times table error.
• There will never be another kind of mistake in the product, my son doesn't skip digits.

For each wrong digit, return an array of two or three elements:

• Position of the digit from the left or right, 0- or 1-indexed (your choice must be consistent). Keep in mind that, if the leftmost digit is absent due to a carryover error, then it's still the leftmost digit and the place has the relevant index.
• Correct carryover, if the mistake was a carryover error, or omitted otherwise. You may also put a 0 instead of omitting the element (you can't blame my son for forgetting to add a zero carryover!), but be consistent.
• Correct digit.

---

Rules

• The numbers will all be positive integers.
• The multiplicand will be an integer from 1 to 9, inclusive.
• You can get the three numbers via any reasonable way you want.
• The output can be in any order, as can the elements of each array, as long as the latter is consistent.
• You may not make use of any standard loophole.
• This is a code-golf challenge, so the shortest answer, measured in bytes, wins.

---

Test cases

Multiplier, Multiplicand, Product -> Mistakes (0-indexed from the left, possibly absent carryover)

5, 3, 15 -> [] (15)
3, 5, 5 -> [[0, 1, 1]] (05 -> 15)
7, 3, 31 -> [[0, 2]] (31 -> 21)
1551, 9, 4959 -> [[0, 1, 1], [1, 4, 3]] (04959 -> 14959 -> 13959)
2121, 7, 14847 -> [] (14847)
2121, 7, 4727 -> [[0, 1, 1], [2, 1, 8], [3, 4]] (04727 -> 14727 -> 14827 -> 14847)
33333, 9, 11111 -> [[0, 2, 2], [1, 9], [2, 9], [3, 9], [4, 9], [5, 7]] (011111 -> 211111 -> 291111 -> 299111 -> 299911 -> 299991 -> 299997)

---

Sandbox

• Is the challenge unclear?
• Is the output format weird or too strict?

Answer 25

Sandbox Notes

• Any other/better tags?
• Is my math right?

Knot Function

code-golf knot-theory function

TL;DR: Define a closed curve in 3D space that forms a knot.

A function \$f : [0,1] \to \mathbb R^3\$ is considered a loop function if the following conditions hold:

• It is continuous.
• \$f(0) = f(1)\$.
• It is injective everywhere else.

Intuitively, this means that the function traces out a curve in 3D space that does not intersect itself.

Let the set of loop functions be denoted \$\text{Loop}\$. One such function is \$\text{circle}(t) = (0, \sin 2\pi t, \cos 2\pi t)\$, which traces out a circle in 3D space.

A function \$f : \text{Loop}\$ is considered a knot function if there exists no continuous function \$d : [0,1] \to \text {Loop}\$ such that \$d(0) = f\$ and \$d(1) = \text{circle}\$. Intuitively, this means that the loop that the function traces out cannot be continuously deformed into a circle without intersecting itself.

The Task

Write a program or function that implements a knot function, where real numbers are replaced with (to best approximation) floating point numbers.

This is code-golf, so the shortest valid answer (measured in bytes) wins.

Answer 26

Print the sum of the previous answer's ASCII values

answer-chaining

Challenge

Output the sum of the previous answer's characters. For example, if the previous answer was print(25), the next answer would have to output the next answer would have to output 741.

Initial Answer

The initial answer has to output the number 1000

Rules

• Your code can only use ascii characters (sorry Jelly), no extended-ASCII or Unicode characters.
• Your output can be in Decimal, Unary or Base 256 (represented by ASCII characters)
• You cannot use a language that has been used before. (Note: Different versions of the same language are allowed, like Python 2 and Python 3)
• To prevent overly long languages (such as Unary) ruining the chain, your answer cannot be longer then 1000000 bytes.
• The same person cannot post twice in a row
• If two users post "at the same time", the earlier one will stand
• If a solution breaks one of these rules, it and all answers that chain off of it will be deleted
• Don't edit your code after you've posted it, otherwise it could invalidate code that chains off of it

Winning

The winner of the challenge is whoever has posted the most recent answer, since it will get harder and harder the more languages that are used.

Answer 27

I'm sorry, Code Golf

code-golf ascii-art

This challenge is inspired by a series of Garfield-inspired artwork in which Garfield is depicted as a horror creature, stalking his owner, Jon. Commonly referred to as "Creepy Garfield", the line "I'm sorry, Jon" can be found in one of the earliest Creepy Garfield images, created by DubbleBaby.

William Burke's Depiction

After being used over and over again by the Code Golf community, our beloved Jimmy has transformed - no longer bound to his weak, mortal body. He has become the embodiment of spaghetti code, the ascii manifestation of hours-long debugging sessions.

---

Your Task:

Take 3 ordered numerical inputs and output Jimmy's body

Inputs

Input is received in the form x y z where:

x is the number of left limbs (integer between 1 & 10)
y is the number of right limbs (integer between 1 & 10)
z is the number of heads (integer between 1 & 10)

----Sample Input----
2 8 1

Meta Note: I don't think increasing the possible amount of body parts will influence the solutions but please let me know if you think they should be higher.

Body Parts

Head =          <o>
Left Limb =     /
Right Limb =    \
Filler Limb =   |
Body Piece =    0

Body Generation Rules

   1. Left limbs must be attached to the left side of a body piece
    (excl rule 3)
    - Correct:  /0
    - Incorrect: /<o>
    - Incorrect: 0/
    - Incorrect: /0\0\

2. Right limbs must be attached to the right side of a body piece
    (excl rule 3)
    - Correct: 0\
    - Incorrect: <o>\
    - Incorrect: \0

3. Limbs must not touch
    - Correct: /00\
    - Incorrect: /0\/0\

4. An external body piece without a limb must have a | in its place
    - Correct: /0|
    - Correct: |0|
    - Correct: /00\
    - Incorrect: /0
    - Incorrect: 0\

5. Heads must be between body pieces (horizontally not vertically)
    - Correct: 0<o>0
    - Incorrect: 0<o><o>0
    - Incorrect: 0<o>

6. All lines must be aligned centre
    - Correct:      /0\
                  /0<o>0|
                    /0\

    - Incorrect:    /0\
                    /0<o>0|
                    /0\

7. The bottom line of Jimmy's body must always contain a left and right limb
    - Correct:      /0\
                  /0<o>0|
                    /0\

    - Incorrect:    /0\
                  /0<o>0\
                    /0|

8. Jimmy's body must be whole and cannot be separated into sections
    - Correct:    /0\
                /0<o>0|

    - Incorrect:    /0\   /0\   |0<o>0|

    - Incorrect:      /0\

                    /0<o>0|

Examples

Input:
2 8 2

Sample Output:

/0<o>0<o>0\
    |0\
    |0\
    |0\
    |0\
    |0\
    |0\
    /0\

    OR

  /0\
  |0\
|0<o>0\
  |0\
  |0\
|0<o>0\
  |0\
  /0\

---

Rules & Win Conditions

1. You may receive the stated input via any method into a program or function.
2. You may display the output in any clear and discernible way.
3. Your output must obey all Body Generation Rules.
4. The previous 3 rules must be followed for all 1000 combinations of inputs.
5. Standard loophole rules apply.

As this is code-golf, least amount of code in bytes wins.

Answer 28

Minimum string attractors

code-golf string optimization

---

String attractors

Let \$S\$ be a string of length \$n\$. An attractor of \$S\$ is a subset of indices \$A \subset \{0, \ldots, n-1\}\$ such that every nonempty contiguous substring \$S[i \ldots j]\$ of \$S\$ has an occurrence \$S[i' \ldots j']\$ whose index set \$[i' \ldots j']\$ intersects \$A\$. A minimum attractor is one with minimal size. Minimum attractors can be used to implement very efficient string compression algorithms. In this challenge, your task is to find a minimum attractor for a given string.

Example

Consider the string acabaccabc. Using 0-based indexing, one of its attractors is \$A = \{2,3,5,8\}\$. This graphic shows the positions of \$A\$:

acabaccabc
  ^^ ^  ^

For example, the occurrence of the substring ac in the beginning doesn't intersect \$A\$, but there is another occurrence after the first b that does. It turns out that no attractor of size 3 exists for this string, so \$A\$ is a minimum attractor.

Specifications

Your input is a nonempty string of lowercase ASCII characters. Your output is a minimum attractor for this string, in any reasonable format. You can use either 0-based or 1-based indexing.

There may be several choices for the minimum attractor. In that case you may return any one of them, but only one.

The lowest byte count wins.

Test cases

These are 0-indexed and show one possible output.

a -> [0]
aaa -> [0]
ababab -> [0,1]
qgqqgq -> [1,2]
abcbacaa -> [1,3,5,6]
abcdefgh -> [0,1,2,3,4,5,6,7]
jejjeeje -> [2,3,5]
sttststt -> [1,5]
ykkkkvyk -> [0,2,5]
assassins -> [0,2,6,7]
acabaccabc -> [2,4,6,8]
ssssssjjjsjj -> [5,8]
hrhrhhrhhhrr -> [3,7,10]
fubuaabubuau -> [0,1,4,6,10]
jjaahajjhahaaahjjh -> [2,6,8,11,14]

Answer 29

Posted here

Answer 30

Check If A Binary Search Tree Is Balanced

Now posted on CodeGolf.StackExchange.com:

Write The Shortest Program To Check If A Binary Tree Is Balanced