Questions tagged [open-ended-function]
For challenges where an exact output is not required but some property must still be fulfilled.
120 questions
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Computing Pi with iF*ck
Objective
Compute \$\pi\$ using nothing but \$i\$ (\$\sqrt{-1}\$).
Guidelines
ONLY exponentiation and multiplication may be used (i.e. \$i^i\$ or \$ii\$)
No additional symbols may be used (so no ...
- 521
8
votes
18
answers
1k
views
Output five hundred different valid Roman numerals [closed]
Output any 500 different valid Roman numerals in the range 1 to 3999, in uppercase. Code golf.
- 8,074
11
votes
5
answers
856
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Show order equivalence between the rationals and the binary fractions
Write a function \$f\$ which takes rational numbers and gives binary fractions (rational numbers whose denominator is a power of two) which is bijective and preserves order.
That means:
Different ...
- 103k
-5
votes
7
answers
490
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Produce 2025 in any human language, without those characters in your code
It's 2025! Write a function/program that outputs this number in words.
There are two twists:
You can write it out in (almost) any human language (including English).
None of the characters in your ...
- 8,074
10
votes
2
answers
521
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Make a pretty cryptic crossword grid
Write a function/program that generates an aesthetically pleasing square cryptic crossword grid for a given size N. You do not need to include numbers.
The rules for aesthetically pleasing are:
The ...
- 8,074
6
votes
3
answers
651
views
Implement any rotation-invariant function on colored dodecahedrons
Each of a regular dodecahedron's 12 faces can be painted either red or blue. Your task is to implement a function \$f\$ that takes a painted dodecahedron (as 12 booleans, in whatever order and format ...
- 871
4
votes
3
answers
519
views
Operators modify in place, fix my expressions [closed]
I'm using a language "MutFk" where the basic operators like "+" and "*" actually modify the left hand side of the expression, and also return the modified version. For ...
- 14.4k
14
votes
7
answers
942
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Implement any 10-ary truth function with cyclic symmetry
Implement a function \$f\$ that takes 10 boolean inputs and returns a boolean.
The only requirement on \$f\$ is that it satisfies the identity
$$
f(x_1,x_2,x_3,x_4,x_5,x_6,x_7,x_8,x_9,x_{10})=f(x_2,...
- 871
33
votes
26
answers
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Print 4 billion if statements
Recently (okay, December 2023, I'm a little late) there's been a meme going around about a program checking if a 32-bit unsigned integer is even or odd using four billion if statements:
...
- 46.2k
9
votes
10
answers
2k
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Figure out which of your friends reveals confidential information to the media!
Exposition
You send secret information to 100 of your friends, and the next day you discover that the information has been published! Who could have revealed it?
To determine that, you number your ...
- 14.2k
8
votes
12
answers
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Tic-tac-toe encode them all
I decided to create a complete guide to the great game of tic-tac-toe.
I expected it to be extremely popular, so to save on paper while printing it I decided to encode all possible game positions.
I ...
- 927
0
votes
4
answers
339
views
Implement a Monad
A monad is a type that wraps another type, that represents the available operations on the wrapped type. Monads have the following associated operations, where M is ...
- 11.5k
9
votes
3
answers
301
views
Convert to Chomsky normal form
Let a context-free language be specified by its production rules and start symbol, e.g.
S -> AbB | C
C -> b | c
B -> AA | AC
A -> a | ε
Here and in the ...
- 4,749
6
votes
1
answer
461
views
Counterexample to Shapiro inequality
Input: A positive integer n such that
n is even and greater than 12 or
n is odd and greater ...
- 2,518
11
votes
4
answers
2k
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Output a 1-2-3-5-7... sequence
Follow-up of my previous challenge, inspired by @emanresu A's question, and proven possible by @att (Mathematica solution linked)
For the purposes of this challenge, a 1-2-3-5-7... sequence is an ...
- 3,053
22
votes
15
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Output a 1-2-3 sequence
For the purposes of this challenge, a 1-2-3 sequence is an infinite sequence of increasing positive integers such that for any positive integer \$n\$, exactly one of \$n, 2n,\$ and \$3n\$ appears in ...
- 3,053
12
votes
7
answers
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Horsey sightseeing
A knight's tour is a sequence of moves of a knight on a chessboard such that the knight visits every square only once. For those who are not aware of how knights in chess work, knights are capable of ...
- 17.4k
21
votes
9
answers
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Output an infinitely proportional sequence
In this challenge, an infinitely proportional sequence is defined as a infinite sequence of positive integers such that:
All positive integers are contained infinitely many times within the sequence.
...
- 46.2k
17
votes
12
answers
1k
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Encode the input to exclude a given character (part 1)
Your task is to write 2 functions/programs. They may share code.
The first function must, given a string and a character, output a new string that does not contain that character.
The second function ...
- 14.4k
8
votes
0
answers
272
views
Give the best Chaitin incompleteness bound
This was originally a pure mathematics question, but I think I've got the best chance for an answer here.
The Challenge
For concreteness, consider Peano Arithmetic (PA). For some language L of your ...
- 261
11
votes
9
answers
2k
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Make a super fair number
An even distribution number is a number such that if you select any of it's digits at random the probability of it being any particular value (e.g. 0 or ...
- 103k
16
votes
3
answers
568
views
Convert numbers to dice patterns
The way points are assigned on a dice follows a regular pattern, the center dot is present if and only if the number is odd. To represent the even numbers, pairs of dots on opposite sides of the ...
- 6,095
21
votes
23
answers
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Be big more often
Related
You are a manager at a large number factory. You want to show everyone your business is doing well, by showing randomly chosen samples. Unfortunately, your business is not doing that well. But ...
17
votes
5
answers
886
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Prefix code generator
In this challenge, we consider an encoding from positive integers (up to a limit) to binary sequences. Some examples:
...
- 79.3k
13
votes
9
answers
3k
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Give the fool's Fibonacci sequence
Recently I asked for tips on improving some code-golf of mine. The code was supposed to output every third value of the Fibonacci sequence starting with 2:
...
- 103k
13
votes
8
answers
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Generate all linked chains
A followup to this challenge by Jeremy Collprav, inspired by DLosc solving this in Regenerate. Some sections copied from the linked challenge.
Linking chains
We define a chain to be a string ...
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Sudoku as a SAT problem
Background
An interesting way to solve a Sudoku puzzle is to represent it as a Boolean satisfiability problem, and then feed it to a SAT solver.
A Boolean Satisfiability Problem (abbreviated as SAT ...
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votes
10
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Adjacent Items Sorting
Given a list, L, of sets of numbers like this:
[[1], [0,2,3], [3,1], [1,2,3]]
Output a single list of numbers such that 2 ...
- 14.4k
24
votes
5
answers
3k
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Add two real numbers ... probably
The problem statement here is pretty simple, take two real numbers on the range [0,1) as input and output their sum, with probability 1.
The catch here is that there are a lot of real numbers. There ...
- 103k
12
votes
7
answers
883
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Mapping Passing Through Point
(Inspired by this challenge.)
Given six real values in three pairs: \$(x_1, x_2), (y_1, y_2),\$ and \$(x_0, y_0)\$, where \$x_1 < x_0 < x_2\$ and \$y_1 < y_0 < y_2\$, create a function ...
- 7,465
0
votes
6
answers
534
views
Generate number from given range
Your function must accept three numbers in any order:
A signed real number (or ±Infinity) - The number (N) for which you have ...
- 1,472
13
votes
14
answers
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Generate a permutation from the high-water marks
Given a permutation, we can define its high-water marks as the indices in which its cumulative maximum increases, or, equivalently, indices with values bigger than all previous values.
For example, ...
- 10.9k
8
votes
3
answers
446
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Injectively saturate bit strings
It can be easily proven using Hall's marriage theorem that given fixed \$n\$ and \$k<n/2\$, there is an injective (one-to-one) function from all \$n\$-bit strings with \$k\$ ones to \$n\$-bit ...
- 4,749
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votes
6
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Approximate a root of an odd degree polynomial
Every odd degree polynomial has at least one real root. However this root does not have to be a rational number so your task is to output a sequence of rational numbers that approximates it.
Rules
...
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20
votes
9
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Split some points
proposed by @Adám in chat
Given an even number of finite points return a line \$y=mx+b\$ that evenly splits the points on both sides.
Specs
Take a list of distinct points \$(x,y)\$ (or a list of x-...
- 9,538
22
votes
17
answers
3k
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Don't repeat yourself
In this challenge you will be tasked with implementing a sequence of natural numbers such that:
Each number appears a natural number of times
No two numbers appear the same number of times
No two ...
- 103k
8
votes
4
answers
497
views
Number-only switch
Write a function that takes an ASCII-printable-only (all charcodes ∈ [32..126]) string input x and provides an ASCII-printable-only output string ...
- 32.7k
5
votes
2
answers
401
views
Don't output the file 2
Last time you were required to write program that output a file, such that no byte is same as original file. The request meant to let everyone carry part of information, but it ends up that everyone ...
- 32.7k
20
votes
10
answers
2k
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Enumerate the rationals
The cardinality of the set \$\mathbb Q\$ of rational numbers is known to be exactly the same as that of the set \$\mathbb Z\$ of integers. This means that it is possible to construct a bijection ...
- 22.8k
4
votes
1
answer
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views
Show a balanced binary tree
Given an integer \$n > 1\$, output a balanced binary tree with \$n\$ leaf nodes.
The tree should be constructed out of (space), ...
- 7,465
7
votes
9
answers
421
views
Incomparable partitions
A partition of a list \$A\$ is a way of splitting \$A\$ up into smaller parts, concretely it is list of lists that when concatenated gives back \$A\$.
For example ...
- 103k
21
votes
11
answers
2k
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Create a nibble shorthand
I recently stumbled across this image on wikimedia commons. It's a little bit of an information overload at first, but after examining it a bit it shows an interesting number system for writing ...
- 103k
29
votes
20
answers
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Transform characters of your choice into "Hello, world!"
Write a program or function that takes a character as input and outputs a character. Also, choose a list of 13 distinct ASCII printable characters (32-126). When a character from this list is passed ...
- 1,925
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votes
5
answers
406
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Generate number set with conditions using n numbers
Generate \$T=\{T_1,...,T_x\}\$, the minimum number of \$k\$-length subsets of \$\{1,...,n\}\$ such that every \$v\$-length subset of \$\{1,...,n\}\$ is a subset of some set in \$T\$
Here, \$n > k &...
- 179
23
votes
26
answers
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Generate an arbitrary half of a string
Given a string \$ x \$, we say another string \$ y \$ is half of it, if both of the following properties are true:
\$ y \$ is a (not necessarily continuous) subsequence of \$ x \$ - there exists a ...
- 10.9k
2
votes
0
answers
52
views
Bijective Function (mapping integer to arbitrarily large integer tuple) [duplicate]
Find a bijective function which maps integers to arbitrarily large tuples of integers. Given the input \$n\$, output the tuple it matches to.
Edit: The empty tuple is included in the mapping.
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15
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Enumerate all pure sets
In set theory, a set is an unordered group of unique elements. A pure set is either the empty set \$\{\}\$ or a set containing only pure sets, like \$\{\{\},\{\{\}\}\}\$.
Your challenge is to write a ...
- 46.2k
22
votes
26
answers
3k
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Give f and g that sometimes commute
Let \$Z\$ be either the integers, the positive integers, or the non-zero integers; pick whatever's convenient. Give two functions \$f\$ and \$g\$, each \$Z \to Z\$, such that:
\$f(g(a)) = g(f(a))\$, ...
- 1,391
17
votes
16
answers
2k
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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 ...
- 533
14
votes
3
answers
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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 ...
- 16.9k