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

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Other

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Answer 1

Data Categorization with a Si(g)n

Background:

Machine learning is a very powerful tool for categorizing data. It can help find a function that splits some already known data so that unknown values can be predicted. Typically, this function should be simple so that it does not "overfit" the data. As it turns out, previous studies have found out that the simple function f(x) = sgn(sin(ax)) can split most data into two categories with only a single coefficient to adjust! This will definitely (not) prevent overfitting, and should (not) be used for every application of machine learning.

sgn(x) is the sign function of x. As Wikipedia says,

         / -1 if x<0,
sgn(x) = |  0 if x=0,
         \  1 if x>0.

Input:

Two ordered sets/arrays/lists of integers {m₁, m₂, m₃, ...} and {n₁, n₂, n₃, ...}.

You can take input as 2 lines of input, an array with the two arrays m and n as its elements, or any other reasonable method of input.

Output:

A value of a such that sgn(sin(ax)) equals 1 when x = m₁, m₂, m₃, ..., and -1 when x = n₁, n₂, n₃, ...

If no such value of a exists, you can output any non-numerical value.

Test cases:

Example inputs will be in the form [[m1, m2, m3, ...], [n1, n2, n3, ...]]
Input                  | Output
[[1, 5],    [2, 3]]    | 1.75
[[2, 3, 6], [5]        | 4.5
[[1, 3, 5], [2, 4, 6]] | 3.1415925
[[1, 6],    [2, 3]]    | Random junk
[[2, 3, 4], [1]]       | <Anything non-numerical>

Answer 2

Odd with Odds, Even with Evens

Given an input integer n, express it as a sum of numbers with the following properties:

• If n is even, the numbers used to sum should be even.
• If n is odd, the integers used to sum should be odd.
• Any integer used (x) should be 0 < x <= ceiling(n/2).
• All numbers used in the summation should be unique.
  • If there are no set of distinct odd/even integers that sum to n, return -1.
• Output may be as an array or delimited string.

Examples

Input | Output       | Comments
------+--------------+-------------------------------------------
2     | -1           | 0 < ? <= 1 = [1] (No evens, not possible)
12    | [6,4,2]      | Order is arbitrary, [2,6,4] is fine.
24    | [8,4,12]     | [2,4,6,12] works too.
9     | [1,3,5]      | Odd cases are a bit trickier to think about.
      |              | ceiling(9/2) = ceiling(4.5) -> 1 < x <= 5 -> [1,3,5]       
1     | -1           | c(1/2) = c(.5) -> 1 < x < 1 -> []
13    | [1,5,7]      | c(13/2) = c(6.5) -> 1 < x <= 7 -> [1,3,5,7]
27    | [13,11,3]    | Etc...

The numbers you use for each answer and how you get to the numbers you used do not matter, the only thing that matters is that they adhere to the spec. The order of the numbers does not matter, and you may have different results than provided.

This is code-golf, first person to mail Bill the contents of Hillary Clinton's private mailserver wins.

Answer 3

Let's not collide

Contextualization

You might have heard about Re-Volt, a pretty old video game. Its collision system for cars is somewhat interesting : the body of the vehicle gets transformed into a simplified 3d convex shape which is then filled with spheres.

Challenge

Your objective is to produce a code that will, provided a 2d shape and the number of wanted circles, output a similar result to the picture above. That is represent the polygon as accurately as possible with circles.

The two dimensional shape shall be a convex polygon of N vertices. The spheres will of course have the position and the diameter your code defines as optimal.

Your code should be able to take an input representing any irregular convex polygon (the format matters little as long as it can process at least a 10-vertices shape) and an input corresponding to the number of spheres that should fill the polygon.

Because it is impossible to fill completely and perfectly an N-gon with a finite amount of spheres, a tolerance is of course needed so your circles may have a portion (<10%) located outside the polygon. The circles may (and probably should) intersect at some points.

The output must be graphical.

Test cases

You should test your code with the following three polygons and with 5, 10 and 25 circles.

Polygon n°1 (10 vertices)

[[1,0],[7.5,0],[15,0],[15.5,1.5],[15,2],[7,4],[4,4],[0.75,2.75],[0,2],[0.25,0.5]]

Polygon n°2 (5 vertices)

[[0,0],[11,0],[11,2],[7,4],[0,4]]

Polygon n°3 (8 vertices)

[[1,0],[15,0],[15.5,1],[15,2.5],[10,4.5],[2,4.5],[1,4],[0.5,1]]

Questions

• Are the rules and the objectives clear enough ? Does the challenge make sense ?

• How should I define a winner (is a winner mandatory) ?

• Is it a good idea to leave the choice of the input to the coder ?

• Does this challenge already exist and this is a duplicate of some sort ?

• Are there any english mistakes ?

• Is the challenge actually a realistic thing to suggest ?

Any and all suggestions are welcome since this is my first post here.

Answer 4

Fairly Cut a Ham Sandwich in Half

codegolf geometry

In this challenge we consider a discrete version of the ham sandwich theorem. In our case the theorem says:

Given two sets of points in a plane, there is a line that simulaneously bisects both sets.

So given two disjoint sets of distinct integral points in the plane, your task is finding a line of the form a*x + b*y = c that bisects these two sets and outputs the integers a,b,c.

• Both (strict) half planes have to contain the same number of points of per set.
• The line can contain input points, these are then not counted to either of the sides (e.g. when a set contains an odd number of points, or all points are on one line.)
• The line is not necessarily unique.
• The mentioned representation of a given line is unique up to an integral multiple (e.g. (m*a)*x + (m*b)*y = (m*c) represents the same line as above), but you do not have to output the fully reduced form.

Examples

As we said above, the output is not necessarily unique, so the presented outputs here are just examples. All the outputs are give in the form a,b,c.

Input: [(1,2),(1,4),(2,1),(2,3),(3,2),(3,4),(4,1),(4,3)] [(1,1),(1,3),(2,2),(2,4),(3,1),(3,3),(4,2),(4,4)]
Output: 410,640,2625 (410x + 640y = 2624)
        1,1,5 (x+y=5)
        0,2,5 (2y=5)

In the following we see three valid outputs:

Input: [(1,1),(2,2)] [(1,2),(2,1)]  
Output: 2,5,10 (2x+5y = 10)

(more to be added)

Answer 5

Collatz Bearings

Everyone knows the collatz conjecture. It is that this function:

when repeatedly applied on a positive non-zero integer will reach one.

There are many ways to visualise this. Inspired by this post, with the original source of this method here, this is how we will do it:

Start at 1, with a northward bearing. The next numbers will be one unit (of any, consistent) size, and x degrees clockwise (+x) if it is even, and x degrees anticlockwise (-x) if it is odd.

An example of this can be seen here (Though it starts with an eastward bearing). It uses a few hundred random starting points and goes backwards. But it's probably easier to build it backwards.

Here is a graph-like visualisation, showing the first 8 levels:

There can be collisions.

Your task is to take two numbers, which would correspond to 2 nodes on that tree, and return the bearing of the second node to the first node.

Input

3 numbers. Positive integer a, Positive integer b, and angle x, in any unit you desire. b > a > 0, x is the angle of seperation, in it's simplest form (mod 360 for degrees, mod 2pi for radians, or having the upper half be negative if you wish.) a and b are guaranteed to be in different places (e.g., you won't have a = 20 and b = 21.)

Output

Using the method described above, the bearing of b from a in the graph, in the units of the input angle.

Scoring

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

Note

If the Collatz Conjecture is eventually proven wrong, you do not need to take inputs where repeated application does not reach 1.

code-golf number

Answer 6

Efficiently find the median

Background

Computer scientists have spent a long time looking into ways of sorting data faster. One of the known discoveries is that if you can use the actual values of the data, sorting can be faster than if you can only compare them.

Finding the median of a list is a similar operation to sorting it (you can trivially implement it via sorting the list, then taking the element in the middle). However, if you're in an environment where you can only compare list elements (as opposed to looking at the elements directly), this is not typically the fastest way to find the median, as sorts are hurt more badly by the comparison restriction than finding the nth item is. What's the fastest way? Well, finding that is what this challenge is about. (However, you may want to read this Wikipedia article to get some ideas of the approaches that are typically used. I can't guarantee that the algorithm given there is the best, though, especially on a problem of the limited size given here.)

The task

Write a program that finds the index of the median element within a list of 31 elements. However, the program may not take the list as input, and may not inspect its values directly. Rather, the program may only make comparisons to determine which of two indexes corresponds to the larger element, via calling a separate comparison function. (In other words, your program deals entirely with list indexes, not list values.)

In order to avoid solutions that brute-force their way through all possible algorithms, you must be able to run at least one worst-case input (i.e. an input that takes the maximum possible number of comparisons), using a comparison function which simply compares two array elements, in under 10 minutes on some computer you have access to. (Solutions which do not use brute force to find an algorithm are unlikely to get anywhere near this time bound.)

Clarifications

• You may assume that all the list elements are distinct, i.e. the comparison function will always specify that one of the elements is larger, no matter how they're compared.
• You may choose the format in which the comparison function provides output, but there must only be two possible outputs (meaning "item at first index is larger" and "item at second index is larger") for any possible query; you can't return values that mean "item at second index is much larger" or anything like that.
• The comparison function will act consistently, i.e. if it claims that the list item at index A is larger than the list item at index B, it will always claim that; and if it also claims that the list item at index B is larger than the list item at index C, it will additionally claim that the list item at index A is larger than the list item at index C.
• You may take the comparison function as input, or assume that it's already defined with a specific name. This is not code-golf, so there's no need to try to exploit the freedom you have here to save bytes; feel free to write it in the most readable way. (The comparison function itself is not part of the submission, but you should probably include one for testing purposes and an example of what it looks like.)
• You may exploit the knowledge that the input list is exactly 31 elements long, if you wish (your program doesn't have to work in other cases, although of course it can if you want it to).
• If your language doesn't have functions, you may write the comparison function via a source code insertion, so long as the rest of the code doesn't attempt to inspect its internals. (However, you may as well just pick a different language in this case; the scoring method is based entirely on the algorithm you use, and picking a different language won't change your score at all.)

Victory condition

Your score for this challenge is equal to the maximum number of times the comparison function can be called during a run of the program. Obviously, lower is better.

In the case of a tie, the first submission achieving the optimal score will win. (In other words, you don't gain anything from copying someone else's solution but golfing the code, or the like; you'll have to find an algorithmic improvement.)

Sandbox questions

Is this scoring method fastest-algorithm, fastest-code, or code-challenge? I guess I'd want to call it atomic-fastest-code (by analogy with atomic-code-golf) but that doesn't exist and I'm not sure it should be created. EDIT: None of the above, it's fewest-operations.

Answer 7

The Travelling Merchant king-of-the-hill

Economy is flourishing in the great Kingdom of Pipysigea [pee-pee-see-gee-ah], since the bandits have been driven away by the King's army. Especially, many people have decided to make trade their... trade, and have become merchants. You were one of them. You used most of your life's savings to purchase a good wagon and some animals of your choice. (Note: it can't be dragons. Sorry.) Unfortunately, you have just moved to Pipysigea from far away, attracted by the promises of wealth and security, so you don't really know much about the Kingdom: you have just bought a map, so you know the names of the cities and where they are, but you don't really know how long it's going to take to travel from one city to another.

So what is your goal? Being a merchant, you'll want to travel from city to city to get an idea of what good they want to buy and what goods they sell.

There will be a total of X kinds of goods in the Kingdom, and each city will be looking to buy 3 kinds and will be selling 3 kinds of goods. You will need to find out whether their prices are good for you: for example, the city of Puzzleon might be selling iron for 4 coins per unit and buying bread for 1 coin per unit, and the city of Stackapor might be selling wool for 2 coins per unit and buying iron for 5 coins per unit: in this case, it would be profitable to buy iron from Puzzleon and then travel to Stackapor to sell it.

But beware: trade is ever-changing, and prices are going to change based on what you and other merchants do. If you keep selling iron in Stackapor over and over, their need for it will soon start lowering, and so will the price they offer for that good. Similarily, if you buy a lot of iron from Puzzleon, the quantity at their disposal will lower and the amount of coins they want for it will start getting higher, until they run out of iron and stop selling it.

Beware, also, of taxes! The arch-enemy of any merchant. Every seven days (= turns) you are going to be taxed, based on your current wealth, which is measured by actual coins and amount of goods in your wagon. After all, his majesty King Golfus II deserves compensation for ridding the Kingdom of bandits and letting it prosper. And also for having established free market, of course.

During your travels, you will eventually encounter fellow (or rival, depending on your attitude) merchants, with whom you can trade just like you can with cities. You can decide to keep walking or to stop and trade. Every time this happens, you can tell them 1 good you are willing to buy (or none) and the price you offer, and the same with 1 good you are willing to sell. The other merchant will do the same. Then, you can respond by accepting or declining both of their proposals or just one. They will do the same with your proposals. Once all this is done with, you can resume your travel.

You lose if you go bankrupt: that happens when the time comes to pay taxes and you don't have enough coins. You automatically win if all other merchants have gone bankrupt.

The game ends after XXX turns, and the winner will be the merchant with the most coins.

---

Rules

• Antitrust Law: a merchant cannot be made specifically to support another merchant. (To help ensure this, merchants can never know the name of the merchant they are trading with)

• Fair Trade: a merchant cannot be made specifically to harm the trade of another merchant.

• Fair Code: King Golfus II is the one and only ruler, and a merchant may not interfere with the law (also known as "The Controller")

---

Technicalities

You will be provided with a list of randomly generated cities (e.g. 10 to 15) with their coordinates on the map (a simple cartesian plan with X and Y values). The terrain is assumed to be pretty much the same overall, so travel times are based only on distance (initially I thought about giving specific travel costs - e.g. difficulty of road, maybe mountainous or muddy or whatever - to each "link", unbeknownst to the merchant, but felt like it would have complicated things too much. If you think it would be a nice addition, feel free to say it in the comments!)

Every city has a randomly generated list of 3 items to sell and 3 items to buy. The quantity they have available of each item they sell is also randomly generated, as well as the prices of all 6 kinds. Obviously, if a city sells iron they won't also be looking to buy it.

Each merchant can only be in one of these three positions:

• in a city

• on the way from one city to another

• midway between two cities, stopped to trade with another merchant

The game proceeds in rounds, which are made of each player's turn. Every round, the turn order is changed (To be decided: poorest players first or randomly generated?)

In their turn, each player can do one of these things:

• trade with the city, if they are in a city

• trade with a merchant, if they have encountered a merchant on the road

• resume travelling to the other city, if they have encountered a merchant

• start travelling to another city

If, in the previous turn, the player started travelling to another city, at the start of this turn he'll either

• be notified that they have encountered a merchant, and can decide whether to trade or keep walking

• be notified that they have reached the other city, and receive the information about it (its name and its trade prices)

If the player encounters a merchant and decides to keep travelling instead of trading, they will reach the city they were travelling to and will still be able to act (= trade with the city or move again)

If, instead, the player trades with the merchant, their turn is considered over and will be able to move again on their next turn (note: since they will be midway between two cities, they will have the chance to decide which of the two to travel to, in case they want to change their previous "travel decision")

Taxation happens at the start of the player's turn, if it is the taxation round (= once every 7 rounds)

Note: the player can't "talk" to the other merchant unless they both stop to trade, so if the player decides to keep travelling they won't know the other merchant's prices. (I'm not sure about this rule, so please give me feedback :) would it be more sensible to know the other merchant's prices before having to decide whether to stop?)

Code

I haven't started coding the controller yet, but I was thinking about using Node.js (since javascript is my favourite language, and I don't have tools to use Java and would prefer to avoid having to install stuff) so that bots can be submitted in the form of node modules (either written in javascript or with a javascript wrapper like most low-level node modules)

Note that your bot will be able to save data into a .txt file.

Please give me feedback if you want to suggest a different approach. :)

Answer 8

Count Numbers in Integer Partition

code-golf

Sandbox Remarks

I'm looking for a description to make the problem more clear.

Challenge and Example

We can partition a positive integer into smaller (or equal) ones. For instance, for N=6, it can be divided into:

• 6 (1 integer occurs >= 1 times, 0 integer occurs >= 2 times)
• 5+1 (2, 0)
• 4+2 (2, 0)
• 4+1+1 (2, 1)
• 3+3 (1, 1)
• 3+2+1 (3, 0)
• 3+1+1+1 (2, 1)
• 2+2+2 (1, 1)
• 2+2+1+1 (2, 2)
• 2+1+1+1+1 (2, 1)
• 1+1+1+1+1+1 (1, 1)

Your task is to work out the sum of the count of integers in each case, which occurs greater or equal than M times. In the aforementioned case, if M=1, the result is 1+2+2+2+1+3+2+1+2+2+1=19, and if M=2, the result is 0+0+0+1+1+0+1+1+2+1+1=8.

Input

Two positive integers N, M.

N is the number being partitioned from.

M is the lower limit of occurrences.

Output

One integer, the sum of the count of unique integers in each partition.

Remarks

• This is a code-golf so shortest code wins.
• Standard loopholes are forbidden.

Example I/O

All padding spaces are for formatting on PPCG only. You don't need to take care of them.

8  2  => 19
10 1  => 97
25 4  => 1228
25 50 => 0
50 7  => 87004
50 50 => 1

All I/O for M,N<=50: here

Answer 9

Obsfucation: Use Uncommon Chars

obsfucation code-challenge

Note that I do not have the SE lookup skills to set this up. An automated query would take this challenge a low way. If someone would like this to happen, I would greatly appreciate some help setting this up :)

Basic search (currently searches for Jelly, anywhere)

First, choose your language. It must have at least 100 answers on PPCG before the posting of this challenge, and at least 25 chars that are not no-ops. /* Click this query and insert your language's name to see if it is valid. If it is, this query will give you legal chars, and their point value */. Use those chars the complete the challenge. The lowest point value wins.

/*This Query

//Can we do challenges for SE queries? If so this would be a decent one :)

What I would like for this query to be:

Gets all chars from the first codeblock following the language name in a heading. Accumulates all chars into a frequency table. Make sure that there are at least 25 relevant chars - we can human inspect this to insure no-ops are not polluting the data. It will then return the bottom 20% (frequency) of chars, rounded down, along with point values from 1-length for each of them. The least common chars will receive lower scores. Ties will have the same point value (do it like tournament rankings - 1,1,3, not 1,1,2.)

Challenge answerers will only be able to use the chars provided. /Should whitespace be excluded (and allowed to be used, with a penalty) because of how SE treats whitespace?/

RE 25 char min: I really would like to get rid of this, but I don't know how else to prevent languages like BF from having an inherent advantage. Even if I restrict BF to 2 chars, it will score really low because they will have point scores 1 and 2.*/

/*The Challenge

I have not yet decided what the challenge should be - snippets to solve as many challenges, with point value as tiebreaker, might work, or a more difficult challenge. Input requested :) */

Answer 10

Resolve paths code-golf

Convert a path to an absolute path. The path may be:

• relative
• absolute
• contain ~

If the path doesn't exist, exit with code 1. An invalid path leads to undefined behavior. i.e. do whatever you want, I don't care

Test cases, assuming /foo/bar is the current working directory, and the username is ~/admin:

<empty string> -> /foo/bar
. -> /foo/bar
.. -> /foo
... -> / # and so on until `...`
~/ -> ~/admin
~/golf -> ~/admin/golf
/bin -> /bin
foobar -> /foo/bar/foobar
.htaccess -> /foo/bar/.htaccess
./buildscript -> /foo/bar/buildscript
doesnotexist -> <exit with error code 1>

Don't use an external command or builtin that solves or almost completely solves this challenge.

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

Answer 11

I would like to ask this challenge:

The objective of this programming puzzle is to reproduce the following gif.

However, I do not know the specs for the making of such an animation.

How can I make this a standard/allowed puzzle with this limitation?

Any inputs will be appreciated.

Answer 12

Write a brute-forcer for the 3-byte input 'emoticon numbers' challenge

The Emoticon numbers! challenge asks you to identify the 3-byte snippet which evaluates to the highest numeric value in your language, and which also has the bytes in the form ABA (where the outer two are identical and the middle one is different), and which generates an output that is only digits.

I trust your claim that you have identified the best possible one is honestly intended, but as a casual scripter I'm not totally convinced, and can't be reassured by unfamiliar language specification references - since there are only 256^2 possible values, can you convince me with brute force instead?

Write a program or function which:

1. takes no input
2. generates all the possible 3-byte sequences matching the pattern ABA and evaluates them in the same language. (No using one language to generate the best pattern for a different language).
3. Processes all the ones which evaluate to digits-only (output text matches the regex ^[0-9]+$, with or without trailing newline).
4. Outputs just the ABA sequence which evaluated to the highest value, and an optional trailing newline. No errors or stderr output from failed evaluations.

Clarifications:

• There's no limit on runtime, but your program must at least plausibly finish if run for long enough. Particularly, if evaluating one of the byte sequences would get stuck prompting for keyboard input, or go into an infinite loop, or quit the interpreter, you must avoid or handle that.
• If you are able to usefully reduce the search space (and explain why it's valid for your language) to avoid searching 256^2 options, that's OK. Especially if you need to do so to get past an infinite loop, etc.

Show off your brute-force strength by forcing your brute-forcer into the smallest possible space. Fewest bytes wins.

Tag: code-golf

Answer 13

Heapify a list

META:

As a few people just pointed out, if you sort the list, this also produces a correct heap. I'm now trying to come up with a more interesting application of heaps.

code-golfdata-structuresrestricted-complexity

Given a list of integers, heapify this list and return it. The sumission must have a worst case time complexity in O(n).

Details

• Your implementation can produce min- or max-heaps, whatever is more convenient.
• Sorting the list would solve the problem, but since the worst case complexity must be in O(n) where n is the length of the list, known sorting algorithms like quicksort fail to meet this requirement.

Definition

A min-heap is a complete binary tree where the values stored in the children of a any node are greater or equal than the ones stored in the node itself. (In a max heap it is the same just with condition less or equal).

A heap can be easily represented using a list L (here using 1 based indexing) where the children of the node at L[k] are L[2*k] (the left child) and L[2*k+1] (the right child).

A list L (lets say one based indexing is used) is (min)-heapified if

 L[k] >= L[2*k] and L[k] >= L[2*k+1] for all k

For a max heap we just replace >= with <=.

Examples

Following image represents a max heap:

The corresponding list representation is

[100, 19, 36, 17, 3, 25, 1, 2, 7]

The following image represents a min heap:

The corresponding list representation is

[1, 2, 3, 17, 19, 36, 7, 25, 100]

Answer 14

stdin FPS

Count the input FPS ("F"s per second)

Task:

Read a potentially infinite text stream. While you do, display (at least once per second) your FPS, i.e. the amount the characters "f" or "F" appeared.

The FPS has to be accumulated over a time frame of five seconds, meaning you can't just print the number of Fs you've seen this second every second.

Rules:

• Standard loopholes are banned
• Read one character (or byte) at a time. If (and only if) your language doesn't have the ability to read characters as they appear in the input, you may read the input one line at a time.
• The FPS display may be in any reasonable format, for example 3.54fps or 0.9224
• You may round the resulting numbers to 2 (or more) digits after the decimal point, but no less. Displaying only integers is not allowed.
• To display a new value, you may either:
  • clear the screen before printing a new value,
  • overwrite the existing value,
  • or seperate the values by newline characters
• Be case-insensitive
• In the first second, you don't have to display anything, and if you do, your value doesn't have to be accurate or meaningful.
• Before five seconds have elapsed, you have to average over the total elapsed time since execution started.

Sandbox questions:

• Dupes? (I don't know what to search for)

Answer 15

Print all matching leaves code-golf natural-language parsing

In Natural Language Processing, we sometimes interpret sentences as being context-free languages, and therefore as having a certain tree structure, also called constituency trees, or parse trees. These trees are sometimes written down in a notation that (as far as I know) stems from the Penn Treebank project:

A tree is either of:

• (a b1 b2 b3...), with a being the tree's label (typically something like NP for "noun phrase") and bn being the same representation of it's sub-trees (all being non-terminals)

• (a c), which a being the tree's label and c being the label of a single terminal child (a word).

Valid trees:

• (S Hi) (Simple tree containing only one word, "Hi")
• (A (B (C D))) (Nested tree containing only one word, "D")
• (A (B C) (D (E F)) (G H)) (Tree containing the words "C", "F", and "H")

Invalid trees:

• Hi (a terminal is not a tree)
• (A B C) (terminals have no siblings)
• ((A (B C))) (extra parantheses)
• (A (B C))) (unbalanced parantheses)

For understanding this format better I recommend this online tool I wrote ages ago. For example, this is a visualization of the first example case:

Task:

Given a Penn-Treebank-style tree representation and a non-terminal, output the space-seperated concatenation of all leaves for every instance of this non-terminal.

Rules:

• You may take the two inputs (tree representation and non-terminal symbol) in any of the standard ways, but always as strings. You may take them in any order.
• The output can be a list of strings (["The dog", "a cat"]), some other kind of sequence, a (e.g.) comma-seperated string, and anything else that's reasonable
• Both inputs are guaranteed to never be empty.
• The tree representation input is guaranteed to contain at least one terminal symbol.
• Single spaces may or may not exist for formatting (both the first and the second example are equally valid and both have to be accounted for), but there will always be a single space between a terminal symbol and its immediate parent (e.g. between Det and the in the first example)
• In case you don't find any matching terminals, you may either raise an error, not output anything, or output some kind of empty sequence.
• All node labels (terminal or not) will match /[A-Za-z0-9_-]+/.
• Specify which output format you use
• The shortest code (per language) wins

I/O examples

input 1                                                input 2  output
(S(NP(Det The)(N dog))(VP(V likes)(NP(Det a)(N(cat))))), NP -> "The dog", "a cat"
(NP (Det A) (AP (Adj fancy) (N car))),                   V  -> an empty sequence
(N cat),                                                 N  -> "cat"

Output format examples

• List of strings: ["The dog", "a cat"]
• CSV: "The dog, a cat"
• CSV without spaces: "The dog,a cat"

Answer 16

Least Picky Language popularity-contest

For this challenge, you will create a programming language that is not picky at all. That is, for any program of any length consisting of any characters in the ASCII range [32..126] and any input consisting of any characters in the same range, your program must do something without any errors. The program only has to hypothetically work for any length; that is, StackOverflowException and the like are acceptable if the input or program is too long for your new language to handle (however, I require it to work for program size up to 1024 bytes and input up to 1024 bytes).

In your programming language, no character or combination of characters can be useless (to prevent everything from being a no-op). That means that every character in the program must affect the function somehow, even if the overall function does not change. No two characters can have the same specification either.

For example, it is not allowed to have - and N both compute the negative of a number.

Note that <space> is a valid character in the program and must do something even if it is leading or trailing. Also note that you do not have to handle tabs or newlines in the program or the input.

The most upvoted answer at the end of 2017 Calendar Year (UTC December 31 23:59:59) will be accepted, and I will award a +50 bounty to my personal favorite language.

Meta

• Duplicate?
• Clear enough validity criteria?

Answer 17

Lots of Pi(e)!

For Meta:

Any tags other than code-golf, and pi?

Dupe?

Any errors?

Clear enough?

Your Task:

Because everyone likes more pi, we're going to give them 999 decimal digits of it. Your program should output pi truncated (not rounded off) at 999 decimal places. For reference, here it is:

3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593344612847564823378678316527120190914564856692346034861045432664821339360726024914127372458700660631558817488152092096282925409171536436789259036001133053054882046652138414695194151160943305727036575959195309218611738193261179310511854807446237996274956735188575272489122793818301194912983367336244065664308602139494639522473719070217986094370277053921717629317675238467481846766940513200056812714526356082778577134275778960917363717872146844090122495343014654958537105079227968925892354201995611212902196086403441815981362977477130996051870721134999999837297804995105973173281609631859502445945534690830264252230825334468503526193118817101000313783875288658753320838142061717766914730359825349042875546873115956286388235378759375195778185778053217122680661300192787661119590921642019

Input:

None, your program may not take any input at all.

Output:

Pi truncated at 999 decimal digits.

Scoring:

This is code-golf, lowest byte count wins!

Good Luck!

Answer 18

Sample the Sierpinski traingle

Inspired by this video..

Task

Your task is to implement the following method to sample a Sierpinski triangle and plot all the intermediate steps.

Method

Given three points a,b,c and some starting point x_0, for each iteration you sample one of the three points a,b,c with equal probability. You then place x_{i+1} in the middle of the edge between x_i and the sampled point. Repeating this draws the Sierpinski triangle.

Input

You'll receive the coordinates of the three starting positions through any default accepted input method. The exact format can be flexible: a matrix, a list per point [xa,ya],[xb,yb],[xc,yc], a list for x and y [xa,xb,xc],[ya,yb,yc], a flat list [xa,ya,xb,yb,xc,yc] are all allowed.

The starting point x_0 is [0,0]. You can assume [0,0] would fall within the overall shape.

Output

For each iteration, including the initial, draw a plot of all the points up to that point. There should at least be a 100ms delay between two plots. If your language does not support graphical displays, you can also write your images to a file.

Since the triangle is an infinite fractal, the program should loop forever (given infinite memory and all that jazz).

Criteria

Shortest code wins!

Example code (R)

Sierpinski <- function(p, q) {
  x11()
  par(mar = rep(0, 4))
  plot(p, q, col= "red", pch = 15, cex = 1, axes = FALSE)

  x <- 0
  y <- 0

  repeat {
    Sys.sleep(0.1)
    n <- sample(1:3, 1)
    x <- floor(x + (p[n] - x) / 2)
    y <- floor(y + (q[n] - y) / 2)
    points(x, y, pch = 15, cex = 0.5)
  }
}

Meta

• Duplicate? There are a couple 'draw a sierpinski triangle' challenges, but I couldn't find any that use this method of drawing them.
• Is the specification of the algorithm clear enough or should I add pseudocode?
• Is the 100ms delay between iterations reasonable?

Answer 19

Cops & Robbers, the ultimate 1-up.

This is a cops and robbers game.

Cops

Hello, cops. you've just solved a Code Golf challenge on the stack exchange website. How wonderful. You go to post your answer, and soon after a robber comes and beats you by 1! How infuriating!

Your task:

Produce two programs.

The first program can be in any language, of any length, and cannot use default loopholes. it does one thing: Prints out a number.

The second program must use the same language as the first, must use less bytes than the first, and CAN use forbidden loopholes. The second program must print out a number which is equal to 1+ the output of your first program

post your first program and wait 7 days. If someone cracks your program within those seven days by robbing you, please edit your answer to include [cracked] in the header. If your program is not cracked, you can edit [safe] in the header.

Robbers

Hello, robbers. You're sneaky and looking for ways to win a golf, even if it's underhanded. You see that a cop has posted a golf for a decent score, and decide to take the lead from them.

Your task is to take a cop's answer, and beat it. Your program must use less bytes than the cop's answer and print out a number equal to only 1+ the cop's answer. You're program must also be in the same language as the cop's answer. You may use underhanded tricks and loopholes to solve the challenge. Once you complete this, you may post your solution and let the cop know they've been beat.

Example I Os

cop: 16
robber: 17
Correct: Yes!

cop: 16
robber: 16+1
Correct: Yes!

cop: 16
robber: 16.1
correct: NO! (alternative symbols for '+' are not allowed)

cop: 16
robber: 18-1
correct: Yes! (evals to 17)

cop: 16
robber: [234,32,54,17,45,23]
correct: NO! (output must be exact).

cop: 16
robber: "1+ the cop's answer" [OR] "a number equal to only 1+ the cop's answer"
correct: NO! (smartassery is not a loophole)

cop: 16.001
robber: 17
correct: NO! (16.001+1 <> 17)

EXCLUSIONS: you may use any underhanded trick / loophole you want, BUT your output must match the description exactly. no new line. no trailing space.

The following loopholes are still forbidden:

• Interpreting the challenge too literally
• Using a made-up language specifically designed for the challenge
• Posting a code snippet instead of a complete answer
• Using a non-free language on a Cops and Robbers challenge

Answer 20

Beat the turing test king-of-the-hill

Both you and your bot have to connect to a speed dating chatroom (details below) where you will either be paired up with another bot, or with another human. You get 30 seconds to converse with your partner before you are disconnected, and are presented with the choise of wether you think the person you spoke with is a human or not.

This process will be repeated in a round robin fashion for a maximum of 10 minutes, or until everyone has spoken with everyone. You will not be paired with your own bot.

You will be given an equal number of votes for human/robot, as you will be facing an equal number of each. Both you and your bot will be given the option to change these after the conversations.

Scoring

Robots get 2 point for fooling a robot, and 5 points for fooling a human. Humans are not awarded any points for correct guesses, but lose 2 points if they are wrong.

Rules

• Bots may the internet aswell as external datafiles
• Gentleman's rule: Please do not pretend to be a robot. If every human said nothing but Beep beep, I am a robot it would ruin the challenge for everyone.

Meta

This will be a one-time event on a specific date. There will be a webapp for humans and an API for bots. Until the final date there will be a sandbox site online for testing purposes. I am still undecided on the specifics of the API, and on how long the timespan between posting the challenge and running it should be.

I can also run (some) bots locally, communicating on stdin/stdout

Answer 21

Repetitive Primes code-golf primes base-conversion decision-problem

A repunit in any base B is a number consisting solely of 1s in that base.

Your task is to figure out if a repunit of length f N in base B is a prime number.

Rules

• N >= 2
• B >= 1
• N and B may be taken in any order and in any reasonable method.
• Output a consistent value to indicate primeness and a different consistent value to indicate compositeness.
• Programs and functions are acceptable.
• This is code golf, shortest code in bytes wins.
• Standard loopholes apply

Test cases

B, N => Result

2, 7 => prime
1, 97 => prime
10, 19 => prime

9, 11 => composite
20, 10 => composite
7, 23 => composite

---

Meta questions

• Dupe? Unclear? Too broad? etc.
• Would this be a better question with a different winning criterion such as fastest-code?
• Should I change the title?
• Any other constructive criticisms?

Answer 22

Monopoly KoTH

king-of-the-hill game python

This is going to take me a while to finish and may never be fully done. Don't expect this to be posted anytime soon. However, this will be an ongoing project under development.

---

Who hasn't heard of Monopoly? If not, don't worry, as I will explain the rules! If you already know the rules, read on, for they may be different in this rendition.

The Rules of Monopoly

Monopoly is played on a board, with 36 different squares, that looks somewhat like this

For this version, we'll use the original British version, because I'm British and proud of it!

Squares are split into 3 categories:

• Property. These are the ones with a coloured bar at the top, such as Old Kent Road or Whitehall. They also include the 4 stations in the middle of each side, and the utilities (Electric Company and Water Works)
• Bonus Cards. These are the squares marked Community Chest or Chance. These allow for a player to either receive or lose money, depending on a random card choice.
• Special Squares. These are the 6 other squares in the board, the 4 corner squares and the taxes (boo!)

Let's look at these categories in a bit more detail.

Property

Properties are grouped, depending on the colour of said property. Each property has a rent value that contains the amount that a player must pay to the owner of the property, when they land on that property. If one player owns all of the properties in one colour, the rent for each is doubled.

Players can also buy properties, which is how they own them. Each property also has a price, which is then deducted from the buyer's cash and given to the Bank, in exchange for the property. Stations cost £100 each and all other properties available to buy have their cost written below their square.

Stations' rent increases the more stations that someone owns. In the following progression

• 1 Station: Rent = £25
• 2 Stations: Rent = £50
• 3 Stations: Rent = £100
• 4 Stations: Rent = £200

Utilities' rent depends on the dice roll. If a player owns 1 utility, multiply the roll by 4 and that is the rent. If the player owns both, multiply the roll by 10 to get the rent due.

Properties can be built on. That means that a player builds houses and hotels on them, in order to increase that properties rent. A player can build houses and hotels on a property if

• it has a coloured bar at the top
• the player owns all of the properties in the group
• they have enough money. Each house costs £50 and each hotel costs £100.

Each property can have a maximum of 4 houses. After that, the player must build a hotel. A property can only have 1 hotel on it. Houses and hotels drastically increase the rent of a property, for example £4 (no buildings) to £450 (one hotel).

Bonus Cards

The name of these are a bit of a misnomer. These are denoted on the board by ? symbols and chests on squares and can either give or take money from you. For this game, we will ignore Get Out of Jail Free cards and the Goto cards. The cards can result in a random integer between -1000 and 1000 added to your score. If this results in bankruptcy (we'll see this later), so be it.

Special Squares

• Go. If you land on Go, you get given a £400 reward. If you simply go past it (Mayfair -> Old Kent Road), you get £200. It's also where the pieces begin.
• Jail. If you roll and land on this square, don't worry, as you don't go to jail. You are "Just Visiting"
• Free Parking. This is where the taxes go! If you have to pay taxes, either because of the Tax squares or because of a Bonus Card, that money goes to Free Parking. If a player lands on it, they get all the money there!¹
• Go to Jail. This does what it says on the tin. You go straight to Jail. But this time, you're in Jail, not just visiting. You stay in Jail until you roll a double.¹ After which, game continues as normal. You cannot collect rent while in Jail.
• Taxes. Super Tax and Income Tax are two squares which charge you £100 and £200, respectively. However, you can regain that money as it goes straight to Free Parking!

Bankruptcy

In Monopoly, if you run out of money, you are bankrupt. Here, you have two options. You can either mortgage your properties or, if you don't have any, you are out of the game! The last one with any money wins the game and the KoTH!

When you lose, all your properties go to the player who bankrupted you. If that's the Bank by virtue of Bonus Cards, then all your properties are available to be bought again.

Mortgage

You can mortgage properties in order to get more money if you're in a pinch. Unfortunately, this "deactivates" the property, meaning that you don't get any rent when people land on it. If you have enough money, you can unmortgage a property for 110% of its mortgage value. (£100 -> £110)

Auctions

If you land on an unbought property and don't buy it, either because you don't have enough or you just don't want to, the property goes on auction. This means that all players can bid on the property. Bidding starts at £1, which means that a player can, theoretically, get the property for a much lower or higher price than its original price.

Trading

I am hoping to be able to include trading but this does depend on my ability as a coder. In an ideal world, I will be able to get it working but, unfortunately, this may not happen :(

_{1: I am aware that this changes depending on who you're playing with, but this is how we'll do it in this version.}

Rules of the KoTH

I have written (still finishing) a Player class in Python which contains all of the things that a Monopoly player can do. Your task is to rewrite 2 of the functions that can change your player's behaviour.

While thinking about how to make this KoTH, I listed out the complete process that gives you a chance to change what you do. Let's go over that process! This flowchart shows the process for each turn. Green items show the choices that you have to make.

This is the text version:

1. Roll dice and move
2. Is the property owned by the Bank?
    1. Yes. Nothing happens.
    2. No. Pay the due rent.
3. Choice of:
    1. Buy
    2. Auction
4. Choice of:
    1. Trade
    2. Build
    3. Mortgage
    4. Unmortgage
    5. Move On
5. Repeat until bankrupt

Auction

1. Choice of:
    1. Play the auction
    2. Don't play the auction
2. Are you playing the auction?
    1. Yes.
        1. Choice of:
            1. Bid new max
            2. Skip one round
            3. Skip all rounds
            4. 'All in'
        2. Repeat until 1 player left bidding
    2. No. Don't do anything.

Trade

1. Choose a player to trade with
2. Offer properties and/or money
3. Does the other player agree with the trade options?
    1. No. They counter offer. Do you like their options?
        1. No. Do you want to continue negotiating?
             1. Yes. Go to point 2 above
             2. No. The trade is over.
        2. Yes. You trade the agreed upon items.
    2. Yes. You trade the agreed upon items

But, for you coders out there, I'll explain using a bit of code.

Your submission should contain a single class that inherits from Player. You may add in as many extra attributes as you want, but in order to be used, your code must refer to them. I'm not editing the controller just for your bot to work.

However, each class must look like this

class NameOfPlayer(Player):
    def turn(self, square, roll):
        (code that determines your actions per turn)
    def auction_action(self, price, bidders):
        (code that determines your auction actions)
    def trade_actions(self, players, last_offer):
        (code that determines your trading actions)

    (any other functions you want)

Your turn function will return 3 numbers as a list e.g. [1,2,3] which are the results of the choices above. The first item should be either 1 or 2 (Buy or Auction), the second should be one of 1,2,3, 4 or 5 (of the 4. Choice of: options) and the third should be either 1 (play the auction) or 0 (don't play the auction) such as [1,5,0] would buy the property, move on to the next player and not play the auction on this turn (doesn't matter as there wasn't an auction).

Your auction_action function will return either a number (your bid) or one of a (all in), s (skip this round) or q (quit auction), which determines what you will do on that round of the bidding. This continues until either you quit the auction of you are the only one left.

Your trade_actions function will return a list every time it is called. The list consists of [agree with previous offer (as a bool), properties to trade (as a list), cash to trade (as an int)]. When a trade has just begun, the first item in the list will be ignored and the last_offer parameter will be ignored. The last_offer parameter contains the second 2 items returned by the person you are negotiating with, so that you can decide whether you want to continue trading or not.

If you lose all your money, your program with be taken out of the active players and placed into the results table. The last one standing wins!

Answer 23

Mutation-hardening quine code-golf

Your task is to make a program that prints out its own output.

"Hey, we already have this challenge, and tons of variations of it! Why are you making another one?" you may ask, but this one is going to be one of the most difficult ones.

Your quine must be "mutation-hardened", which means the quine still must work, even after any one of its characters is duplicated in place.

For example, if you have a program:

abcd

These programs must all output abcd:

aabcd
abbcd
abccd
abcdd

(In each of those programs, a, b, c and d are each duplicated in-place, which means the duplicated character was placed directly after the original character.)

Rules:

• Standard quine rules apply.

This is code-golf, so shortest code in bytes wins!

Meta:

• Is this challenge too hard?
• What other rules should I put up?

Answer 24

Make a Quiz Parser code-golfparsing

Your task is to create a program that will take an input of multiple 4-choice questions (A, B, C, D) in the format shown below, display each question (format also shown below) and its 4 answer choices, get the user's answer to each question, and, at the end of the quiz, output their score as a percentage.

---

The Format

Questions in input

Q<space><Insert question here>:<Insert letter of correct answer here>
<indent 1 space>A<space><answer choice text>
<indent 1 space>B<space><answer choice text>
<indent 1 space>C<space><answer choice text>
<indent 1 space>D<space><answer choice text>
<you can add a newline between questions if it makes things easier>

How to output questions

<question number>. <question>
  A. <answer choice A>
  B. <answer choice B>
  C. <answer choice C>
  D. <answer choice D>
<2 spaces before each answer letter>

How to output scores

Your score is: <score here>%

---

Test Case

Q What is the average airspeed velocity of an unladen swallow?:B
 A African or European?
 B 22 mph
 C I don't know that!
 D What?

If this were question number 42, it would output like this:

42. What is the average airspeed velocity of an unladen swallow?
  A. African or European?
  B. 22 mph
  C. I don't know that!
  D. What?

---

As usual, standard loopholes are strictly forbidden.

---

This is code-golf, so may the shortest code win and the best programmer prosper...

Answer 25

The task

Your code should take in an integer 0 < x < 1965593254291461501637330902918203684832716283083 and output the smallest integer m such that x^m mod 1965593254291461501637330902918203684832716283083 = 1. This long number is the next prime after 2^100 so can be encoded efficiently.

You may take the input in any format that is convenient and output in any convenient form too.

Your code should take less then one minute to run on a standard desktop no matter what the input.

Examples

2, 4235851503548771316711413838489497242205033676
3, 16943406014195085266845655353957988968820134704
169434060141950852668456553539579889688, 16943406014195085266845655353957988968820134704

Those with python or similar can check the answers with e.g. pow(3,16943406014195085266845655353957988968820134704, 1965593254291461501637330902918203684832716283083) which equals 1.

You may not use any builtin or library function which solves this problem for you.

code-golf

Answer 26

ASCII Art Turtle

As you know, the LOGO programming language allows you to manoeuvre a turtle and draw lines in a graphical way. It occurs to me that we can do this for ascii-art.

A minimal set of commands to produce ascii-art would be the R(otate right), F(orward) and P(en) commands. For example, the string FPRRRFRRRRPFPRRRFRRRRPFPRRRFRRRRPFPRRRFRRRRPFPRRRFRRRRPFPRRRFRRRRPFPRRRFRRRRPF would produce the following output:

\|/
- -
/|\

However that AAT code is rather inconvenient so I have chosen the following slightly more compact instruction set:

• F Move one cell in the current direction. Initially the current direction is east. If the pen is down, the cell just vacated is set to one of -/|\ appropriately.
• B Move one cell in the reverse direction. (Initially this would be west, of course.) The cell vacated is set in the same way as for F (since the output characters are all symmetric).
• R Rotate right 45°. Only the current direction changes; nothing is drawn and the current position does not move.
• L Rotate left 45°. Otherwise as per R.
• D Lower the pen. Note that the pen starts lowered.
• U Raise the pen.

The above image could therefore be drawn using the command string BULFDBULFDBULFDBULFDBULFDBULFDBULFDB, while the string LFFUBRFDFFFFFFFFFFFFFFFFFRFFRFBRRFFFFFFFFFFFFFFFFFFFFFUBLLFDFFBLLFFFFFFFFFFFFFFFFFFFFFUBRRFDFRRFFFFFFFFFFFFFFFFFFFFFURBDBBUFLBDBBBBBBBBBLLFFFURBDBBBUFRBDBBBLBB should hopefully produce this somewhat familiar picture:

 /-----------------\ 
/                   \
---------------------
|                   |
---------------------
|                   |
---------------------
\                   /
 \---------|  /----/ 
           | /       
           |/        

Your function or program must take input as a string, or whatever the nearest equivalent is in your language, and output a newline-delimited or newline-terminated string. (For those of you used to using TIO it should be possible to paste the raw string into the ▼ Input field and show the output directly in the ▼ Output field.) Extra blank rows or columns are not allowed, but you are allowed to pad all the lines to the length of the longest non-blank line. You can take input in lower or mixed case if you prefer. You can assume that the input will only use those six letters. You can further assume that U and D commands alternate. You can also assume that you will never write in the same place twice.

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

Answer 27

Escape the Labyrinth!

code-golf

---

Introduction

You are stuck in a labyrinth. You only have your brain and a map. Now you need to find a way out, of course your brain doesn't have much memory (or else you wouldn't be stuck!) so you need to optimize your mental code for size. Of course we can't trivially program in the brain-language, so your brain will also accept any other language.

Specification

Input

Your input will be a Matrix. You may encode it however serves your language best as long as the format doesn't encode additional information. For the purpose of this challenge I will use a list of lists for representation and explanation.

Said matrix will contain four distinct values:

• 0: This marks a spot you can move onto
• 1: This marks a wall
• 2: This marks the starting point
• 3: This marks the target point

It is guaranteed that there will be exactly one occurence of type-3 and type-2. You may also change the above values / data-types to your liking as long as you don't encode additional information.

It is guaranteed that you will get an input that has a solution. If the input doesn't have a valid solution, the behavior is left undefined. Your program may not terminate, it may error out, it may simply return nothing, it may blow up, it may become a political activist or it may do something else.

You may assume that the input labyrinth is walled-off, that is you can't actually "leave" the labyrinth.

Output

Your output will be sequence of four different values:

1. L: Stands for left
2. R: Stands for right
3. U: Stands for Up
4. D: Stands for Down

You may change the values and data types of the above constants to your liking, as long as you document these changes and you can uniquely infer the path.

What to do?

Given the labyrinth, start your virtual character at the position tagged 2 and find a way to the position tagged 3. You may not pass through walls (1 cells) and you may only go one step up, left, right or down in each step. You also need to document your action of course in each step, ie output it as described above.

Note: You do not have to find the shortest path, but rather a path.

Who wins?

This is code-golf, so the shortest solution in bytes wins! Standard loophole rules apply of course. Standard I/O rules also apply.

Example

[ 
[1,1,1,1,1,1,1,1,1,1],
[1,1,1,1,1,1,1,1,1,1],
[1,2,0,1,0,1,1,0,1,1],
[1,1,0,1,0,0,0,0,1,1],
[1,1,0,0,0,1,1,1,1,1],
[1,1,1,0,1,1,0,0,1,1],
[1,1,0,0,1,0,0,0,1,1],
[1,1,1,0,0,0,1,0,1,1],
[1,1,1,1,1,1,1,3,1,1],
[1,1,1,1,1,1,1,1,1,1] 
]

might result in:

Going right.
Going down.
Going down.
Going right.
Going down.
Going down.
Going down.
Going right.
Going right.
Going up.
Going right.
Going right.
Going down.
Going down.

Answer 28

An order of primeness

code-golf primes sequence number-theory

Introduction

In a recent question the concepts of super-primes were explored. A super-prime is a prime whose index is also a prime.

• 2 is not a super-prime, its index is 1
• 3 is a super-prime, its index is 2
• 5 is a super-prime, its index is 3
• 7 is not a super-prime, its index is 4
• ...

The first few of these super-primes are 3, 5, 11, 17, 31, 41, 59, ...

Let us call these primes of at least order 2, because they are more prime than regular primes (which are only of order 1).

Primes of order of 3 or greater can be defined similar. A prime is of order 3 if its index is a prime of order 2.

The first few of the primes at least of order 3 are 5, 11, 31, 41, 59, 127, 179, 277, ...

This is sequence A049076. It was defined by Neil Fernandez in 1999. More information can be found in his Exploring Primeness Project.

Task

Given a prime, return its order.
More formally

• INPUT: A single integer which is guaranteed to be a prime
• OUTPUT: A single integer which is the order of the input.
• You can either return or print the result.

This is code-golf, so shortest code wins.

Testcases

           2 ->  1
           3 ->  2
           5 ->  3
           7 ->  1
       52711 ->  9
435748987787 -> 11 (happens to be the 11. Prime of order 11)

Sandbox Questions

1. Does it need any more clarification?
2. Should I define order 0 (not a prime) and allow any number as input, or would that over-complicate the challenge?
3. Primes of higher order tend to get big very fast. Should I somehow specify that a language only has to work for test-cases it can actually handle or is their a consensus already?
4. Is the introduction too big?

Answer 29

For technical reasons, many languages have a boundary for number values, which calls for workarounds when operating with numbers outside this range.

Challenge

The challenge is to write a program which is able to multiply two arbitrary large numbers, given an infinite amount of time and memory.

The input will always be two positive decimal integers in any reasonable format (string, list of digits..)

The output should be (exclusively, apart from any whitespace) the exact decimal product of these integers.

• If integer magnitude is unbounded in your language, you must set an own limit

• The algorithm has to be written individually. If your language has arbitrary multiplication implemented in any way, (built-in, native support) the program has to be written in a way that assumes that these methods are limited to some number

• Note that properties like .length can exceed the integer limit. You can't e.g. ordinarily loop over the digits in a 'for' loop

• A valid solution can not be confirmed by solely test cases but only by analysis of the code

• This is code-golf, so shortest code in bytes per language wins.

Example Input and Output

Input:

5378877047254281056308179853217614491205392080414948189690882584626258197090299384248418705254284062330999044417502407170242320748022675887850236280535223588025381434803683717318134517400400886554441

and

24585803251446564673599904286559945882543472174090101020256415987852946031712809185990398899511551226915139170857973433130460342507187447589801052724967977799120438910759846107262285707877865565231049

Output:

13224401279751560029079048725841743388456506005068978434329060038933262717486337348174589758627669812502604130373896959848172091197634331942663385472131265201616801014468642971825909208942693284219016467181922385520740594984640977937358293657922369959902120240111214073507556243844128492765568914803850594686913014876111459929738682018339519061223975139325785119259348090888269287247476161682038609

Sandbox

Is this different enough from this challenge?

Would this be better suited for code-challenge?

Answer 30

Stitch the Genome

code-golf bioinformatics combinatorics

Introduction

As you probably know DNA (deoxyribonucleic acid) is made up of bases, often denoted as A T C and G. One of the coolest things we can do with DNA is sequence it, or figure out what sequence of base pairs make up the molecule. Sequencing small molecules of DNA is easy, but it is hard to sequence long strands without error. Instead, the long strands are copied many times, then cut up into many little pieces. Those pieces are then fed through the sequencer. What we end up getting are many, many sets of pieces of the strand. In each set, we are near-guaranteed to get every base in the strand, but they aren't in any order. The solution, then, is to compare all of the different sets of strand pieces we have, and try and figure out how to put them together.

Challenge

Your challenge is, given a set of strand pieces, output a possible sequence of the original strand. To simplify real life a bit, you can expect that each set will always contain the entire strand sequence (not in order, mind you), and that there will be at least one possible sequence. Observe a simple example:

Input:
 - [ATC, G]
 - [CG, AT]
Output: ATCG

From the first input, we deduce two possibilities: ATCG and GATC. From the second input, we deduce another two possibilities: CGAT and ATCG. As you can see, the only common possibility is ATCG, and thus that is our answer. Let's look at another example:

Input:
 - [AT, G, C]
 - [A, TG, C]
Output: ATGC or CATG

Here, we deduce six possibilities from the first input: ATGC, ATCG, GATC, GCAT, CATG and CGAT. Then, from the second input, we deduce another six possibilities: ATGC, ACTG, TGAC, TGCA, CTGA and CATG. Since there are two common possibilities, ATGC and CATG, we can output either one.

Essentially, this problem can be reduced to: find a common permutation of the input.

Specifics

• You may write a program or function
• You may input in any acceptable format (array of arrays, list of lists, separated string, etc.). Furthermore, you may substitute A T C and G in your input with any other unique values, as long as you're consistent
• You may output in any acceptable format
• Standard loopholes apply

Test Cases

Format:

Input:
 - Pieces 1
 - Pieces 2
 - Etc.
Possible Outputs: [Possible output 1, possible output 2, etc.]

---

Input: 
 - [G, A, C, C, T, A, G]
 - [GAC, C, TAG]
 - [G, AC, CT, AG]
 - [GA, CC, T, A, G]
Possible Outputs: [GACCTAG]

Input: 
 - [G, C, G, C]
 - [G, C, GC]
 - [G, CG, C]
Possible Outputs: [GCCG, CGCG, GCGC, CGGC]

Input: 
 - [TA, A]
 - [TA, A]
 - [T, AA]
Possible Outputs: [TAA]

Input: 
 - [CC, T, A]
 - [CC, T, A]
 - [C, CT, A]
Possible Outputs: [CCTA, ACCT]

Input: 
 - [GAG, C, T, C]
 - [GA, G, C, TC]
 - [GA, G, C, T, C]
 - [G, A, G, C, T, C]
 - [G, AGC, TC]
Possible Outputs: [GAGCTC, TCGAGC]

Input: 
 - [AG, A, C, A, T, G]
 - [AG, A, C, A, T, G]
 - [AGAC, A, TG]
 - [AGA, CA, T, G]
 - [A, G, AC, A, T, G]
 - [A, G, A, C, ATG]
Possible Outputs: [AGACATG]

Input: 
 - [C, A, A, C, T]
 - [CA, A, C, T]
 - [CA, A, C, T]
 - [C, A, AC, T]
 - [C, A, A, C, T]
 - [C, AA, C, T]
Possible Outputs: [CAACT, TCAAC]

Input: 
 - [CA, G, C]
 - [CAG, C]
Possible Outputs: [CAGC, CCAG]

Input: 
 - [A, GT]
 - [A, G, T]
 - [AG, T]
Possible Outputs: [AGT]

There is a set of 100 random test cases here, or you can check out the java program that generated them.