Questions tagged [open-ended-function]
For challenges where an exact output is not required but some property must still be fulfilled.
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Average-ignorant sets of integers
Recently a friend of mine posed the following:
What subset of the integers satisfies the condition if distinct a and b are in the subset, their average is not in the subset? I know the set of non-0 ...
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votes
3
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Sniff out biased random permutations
The brilliant engineers at <enter company you love to hate> have struck again. This time they've "revolutionised" the generation of random permutations. "Every great invention is ...
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votes
9
answers
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Is it irrational?
Your task is to make a program that decides if a real number between 0 and 1 is irrational or not. As stated, this is obviously impossible, so instead we will use the following definition:
...
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15
votes
3
answers
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What was my Wordle play?
Task
Given a winning Wordle play results (clues), the target ("secret") word and a list of words, output a possible sequence of words leading to such results.
The words in the list will be ...
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answers
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Output a random unary string
Your task is simple: output the letter x a random number of times. Every possible length of xs must have a non-zero probability ...
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12
votes
8
answers
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All sequences as substrings
Make a program that outputs a sequence of integers so that every finite sequence of positive integers is a substring (continuous subsequence) of the output.
For example, the following sequence ...
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votes
4
answers
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Output a Steiner quadruple system
A Steiner quadruple system \$SQS(n)\$ is a collection of subsets (blocks) of size 4 of a set \$S\$ of size \$n\$ such that every subset of \$S\$ of size 3 is in exactly one block. It is easy to show ...
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votes
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Don't output the file
This rar file, when decompressed, gives a 65024-byte exe file. Requiring you to output the contents of that file would be ...
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16
votes
4
answers
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Probability breaking sequences
If we have a finite list of elements we can determine the probability of any one element being drawn at random as the number of times it occurs divided by the total number of elements in the list.
For ...
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9
votes
8
answers
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Biggest katlani noun dictionary in 400 bytes
Katlani is a constructed language being designed in chat. In this challenge, your goal is to print the largest dictionary of katlani nouns possible in 400 bytes or less.
Task
In 400 bytes or less, ...
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votes
4
answers
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Egyptian fractions summing to n
An "Egyptian fraction" is a list of distinct fractions with a numerator of \$1\$. For example:
\$
\frac 1 1+ \frac 1 2 + \frac 1 3 + \frac 1 6
\$
The "size" of an Egyptian ...
- 84.4k
13
votes
8
answers
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Compress and decompress
Your task is to make a bidirectional compressor. It takes a list of bytes as input and returns a list of bytes as output. It has the property than whenever it is iterated twice it returns the original ...
- 6,645
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Egyptian fraction representations of 1
An Egyptian fraction is a representation of a rational number using the sum of distinct unit fractions (a unit fraction is of the form \$ \frac 1 x \$ where \$ x \$ is a positive integer).
For all[1] ...
- 18.2k
7
votes
1
answer
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Busy beaver in a coin
\$BB\$ is the busy beaver function, an uncomputable function.
Write a program which when given an integer \$n\$ as input, will output \$BB(n)\$, with at least \$\frac 2 3\$ probability. You can do ...
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votes
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Output every sublist ... eventually
You will be given as input an infinite stream of positive integers.
Your task is to write a program which outputs an infinite sequence of lists with two requirements:
All lists in the output are ...
- 84.4k
18
votes
8
answers
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Make every fixed list
We are to define the idea of a fixed list as follows:
A fixed list is a list of fixed lists.
This definition is recursive so it's useful to look at some examples.
The empty list ...
- 84.4k
18
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Generate a regular graph
Inspired by this Mathematica.SE post
Given two positive integers \$n, k\$ with \$n > k \ge 1\$, output a binary \$n\times n\$ matrix such that every row and column contains exactly \$k\$ 1s, and ...
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Encode integers with some others
Input a non-empty array of positive (greater than 0) integers. Output another non-empty array of positive integers which encode the input array. Output array does not use any numbers used in the input ...
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21
votes
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Kolmogorov-simple numbers
If you visit Code Golf often, you may have heard of Kolmogorov complexity. It's usually defined as the amount of bytes required to express some string in a programming language.
Here the Kolmogorov-...
- 6,645
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votes
11
answers
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Infinite ordinals from a well-ordering
Your task is to write a short program that represents a large (infinite) ordinal, using a well-ordering of the set of positive integers. Your program will take two different positive integers and ...
- 6,645
15
votes
3
answers
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Bijection between \$ \mathbb N \$ and at-most-\$n\$-ary trees
Background
Related: a golflang theory I posted in TNB a while ago
At-most-\$n\$-ary trees are rooted trees where each internal node has between 1 and \$n\$ children (inclusive). Two trees are ...
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10
votes
0
answers
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NP-complete reduction: (grid-)Hamiltonian circuit
Background
Hamiltonian circuit problem is a decision problem which asks whether a given graph has a Hamiltonian circuit, i.e. a cycle that visits every vertex exactly once. This problem is one of the ...
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votes
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Give me odd, even, square, cube, prime and composite 3-digit numbers
Given a string which is guaranteed to be either odd, even, square, ...
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votes
4
answers
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Venn of \$n\$ statements
Given a positive integer \$n\$, output \$n\$ 2D bool images with the same width and height such that:
Each image should be 4-connected, i.e. for each two pixels that are true, you can start from one ...
- 12.7k
9
votes
8
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Encode a Lenguage
The Len(language,encoding) family of languages is a variety of Lenguage derivatives. To encode a program into a Len language, you replace every character with its representation in a certain encoding, ...
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19
votes
1
answer
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Demonstrate some advanced abstract algebra
Consider a binary operator \$*\$ that operates on a set \$S\$. For simplicity's sake, we'll assume that \$*\$ is closed, meaning that its inputs and outputs are always members of \$S\$. This means ...
- 46.7k
10
votes
5
answers
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Rewrite strings without changing their order
Lexicographic Ordering
For this challenge we will be talking about the lexicographic ordering of strings. If you know how to put words in alphabetical order you already understand the basic idea of ...
- 84.4k
15
votes
11
answers
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Generate a mantis's head (symmetrical triangle)
Given guaranteed strictly positive integers \$w\$ and \$n\$, output
An equilateral triangle array with side length \$w\$, filled with two distinct, consistent values. I'll call these ...
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25
votes
10
answers
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Floor of complex number
Background
Complex floor is a domain extension of the mathematical floor function for complex numbers. This is used in some APL languages to implement floor ⌊, ...
- 62.1k
17
votes
3
answers
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views
Compute the uncomputable ... sort of
Implement a function \$f\$ (as a function or complete program), such that
\$
\displaystyle\lim_{n\rightarrow \infty} f(n)
\$
converges to a number which is not a computable number.
Answers will be ...
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votes
63
answers
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Infinitely many ℕ
Background:
A sequence of infinite naturals is a sequence that contains every natural number infinitely many times.
To clarify, every number must be printed multiple times!
The Challenge:
Output a ...
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votes
14
answers
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Golf a bijection \$\mathbb{N}^n\to\mathbb{N}\$
Your task is to write a program which implements a bijection \$\mathbb{N}^n\to\mathbb{N}\$ for \$n \ge 1\$. Your program should take \$n\$ natural numbers as input, in any acceptable method (including ...
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41
votes
21
answers
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Three other numbers
Given three distinct numbers from \$1\$ to \$7\$, output three other distinct numbers from \$1\$ to \$7\$, that is having no numbers in common with the original numbers. Your code must produce a ...
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Shortest total non-primitive recursive function
Natural numbers ≡ \$\mathbb{N}≡\{0,1,2,...\}\$
The submission can be either a program or a function, both cases will henceforth be referred to as "function".
The task is to golf the shortest ...
- 12.8k
19
votes
10
answers
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An unknowably odd function
This challenge initially appeared in this challenge as a an extra brain teaser. I am posting it with permission from the original author so that we can have a formal competition.
Your task here ...
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votes
7
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Define the finite field GF(9)
\$GF(9)\$ or \$GF(3^2)\$ is the smallest finite field whose order isn't a prime or a power of two. Finite fields of prime order aren't particurlarly interesting and there are already challenges for \$...
- 10.5k
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votes
8
answers
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Surjection from one string to two strings
This is the inverse of negative seven's question.
Write a program or function which, given any single, possibly-empty string of printable ASCII (codes \$[32,126]\$) outputs or returns two strings of ...
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votes
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Injection from two strings to one string
Challenge
Write a program that applies an injective function which takes an ordered pair of strings as input and one string as output. In other words, each input must map to a unique output.
...
- 2,181
25
votes
7
answers
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Walk Across a Keyboard
Given a word (or any sequence of letters) as input, you must interpolate between each letter such that each adjacent pair of letters in the result is also adjacent on a QWERTY keyboard, as if you ...
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votes
6
answers
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Golf a number bigger than Loader's number
As a follow up to Shortest terminating program whose output size exceeds Graham's number and Golf a number bigger than TREE(3), I present a new challenge.
Loader's number is a very large number, ...
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votes
7
answers
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Hilbert's binary Hotel
In this challenge you will be asked to implement any function (or full program) that fulfills two properties. Those properties are:
Your function must be an injective (reversible) function from the ...
- 84.4k
15
votes
2
answers
297
views
Program an Uncircularness Score
Your task is to program a mathematical function \$s\$, that takes a nonempty finite set \$A\$ of points in the 2D plane, and outputs an uncircularity score \$s(A)\$ that satisfies following properties:...
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votes
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BigNum Bakeoff Reboot
Some of you may be familiar with the BigNum Bakeoff, which ended up quite interestingly. The goal can more or less be summarized as writing a C program who's output would be the largest, under some ...
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Bijective function ℤ → ℤⁿ
It is trivially possible to create a bijective function from \$\mathbb{Z}\$ (the set of all integers) to \$\mathbb{Z}\$ (e.g. the identity function).
It is also possible to create a bijective ...
- 14.5k
4
votes
20
answers
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views
Any digital permutation
Task
Your task is to output a single integer, with one restriction: its digits must be a permutation of [1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6].
For example, you could output 653443653152432, ...
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Design a commutative injective function between any (restricted) infinite set and unordered pairs thereof
Related, but this only requires positive integers and does not have to be commutative
The Cantor Pairing Function is described in this Wikipedia article. Essentially, it is an operation such that ...
- 40.1k
7
votes
1
answer
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Fabricate Frequently Factored Functions
In one of this question's bonuses I asked you to design a permutation on the natural numbers such that the probability of a random term being odd was \$1\$. Now let's kick it up a notch. I want you ...
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votes
29
answers
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What an Odd Function
Your task here will be to implement a function1 that forms a permutation on the positive integers (A bijection from the positive integers onto themselves). This means that each positive integer ...
- 84.4k
32
votes
6
answers
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Implement true string addition
Many languages allow strings to be "added" with +. However this is really concatenation, a true addition would follow the group axioms:
It is closed (...
- 84.4k
10
votes
4
answers
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Two interwoven chains
In this question I defined a "chain" function as a function that:
is a permutation, meaning that every value maps to and is mapped to by exactly one value.
and allows any value can be obtained from ...
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