Questions tagged [code-golf]
Code-golf is a competition to solve a particular problem in the fewest bytes of source code.
10,633
questions
18
votes
16answers
776 views
Double trace of a square matrix
Inspired by a question (now closed) at Stack Overflow.
Given a square matrix, let its double trace be defined as the sum of the entries from its main diagonal and its anti-diagonal. These are marked ...
-8
votes
0answers
101 views
13
votes
13answers
1k views
Find the smallest solution for this simple equation
Input
4 integers w, x, y, z from the range -999 to 999 inclusive where none of the values is 0.
Output
4 integers a, b, c, d so that aw + bx + cy + dz == 0 where none of the values is 0.
Restrictions
...
13
votes
15answers
1k views
Print Gobar Primes
Gobar primes (A347476) are numbers which give a prime number when 0's and 1's are interchanged in their binary representation.
For example, \$10 = 1010_2\$, and if we flip the bits, we get \$0101_2 = ...
20
votes
9answers
1k views
Self-referential triangle sequence
Output the flattened version of the sequence A297359, which starts like the following:
...
11
votes
8answers
1k views
Find the number of paths in a n×n grid
Information
Given a non-negative odd integer (let's call it \$n\$), find the number of all possible paths which covers all squares and get from the start to end on a grid.
The grid is of size \$n\$×\$...
13
votes
7answers
3k views
Make S + S + ... + S as Large as Possible!
Let \$S \subset \mathbb N_{\geq0}\$ be a subset of the nonnegative integers, and let $$
S^{(k)} = \underbrace{S + S + \dots + S}_{k\ \textrm{times}} = \{ a_1 + a_2 + \dots + a_k : a_i \in S\}.
$$
For ...
14
votes
7answers
1k views
Alphabet Reconstruction
You are a historian studying a long forgotten language. You have just discovered a clay tablet which seems to list all known words in the language, in alphabetical order. Your task is to find this ...
19
votes
3answers
2k views
Crossing a river with weird animals
Background
One kind of river-crossing problems involves two kinds of animals. One such problem reads like this: (all wordings, including animal species, are arbitrary)
A farmer has to cross a river ...
17
votes
7answers
3k views
Is This Scrabble Board Valid?
Background
Scrabble is a word game in which players collaboratively build a board consisting of letter tiles that spell words. Each word must be connected to another word, and players gain points ...
17
votes
31answers
3k views
Pythagorean triples given the hypotenuse
Definition (from Wikipedia)
A Pythagorean triple consists of three positive integers a, b, and c, such that a² + b² = c².
The typical example of a Pythagorean triple is (3,4,5): 3² + 4² = 9 + 16 = 25 ...
18
votes
15answers
2k views
Is it a prefix normal word?
Prefix normal words arise in the context of binary jumbled pattern matching. A binary word \$w\$ consisting of \$0\$s and \$1\$s is said to be prefix normal * if, among all of its substrings, none ...
23
votes
41answers
2k views
Swap Two Values in a List
Introduction:
Although we have a lot of challenges where swapping two items in a list is a subtask, like Single swaps of an array; Swap to Sort an Array; \$n\$ swaps into a nop; etc., we don't have ...
6
votes
2answers
226 views
Every Pong is Abelian
Part of the lean Language of the Month
A pong* is a set \$P\$ with an operation \$+\$, that satisfies the following properties:
\$
\forall a, b \in P : (b + b) + a = a\\
\forall a, b \in P : a + (b + ...
14
votes
7answers
817 views
Maybe fractal sequence?
Background
A fractal sequence (Wikipedia; MathWorld) is an infinite sequence of positive integers meeting the following conditions:
Each positive integer appears infinitely many times in the sequence....
12
votes
0answers
332 views
(t)h(e)(i)(r)(m)
Sometimes authors will write (s)he as a stand in for she or he and for some reason they don'...
17
votes
11answers
1k views
How many values of this type?
Background
The number of values for a given type is called the cardinality of that type, and that of type T is written as |T|.
Haskell and a few other languages ...
9
votes
2answers
466 views
Lean golf: List Game Lv2 (is_in_append, is_in_rev)
The title is an homage of the Natural Number Game, which is a nice interactive tutorial into proving certain properties of natural numbers in Lean.
The definitions used in Lv1 will be reused here. I'...
8
votes
2answers
561 views
Follow the border
Inspired by Is this Flow Free puzzle trivial? by @Bubbler. Lengthy chunks of this challenge are borrowed from there. This may be one step of a solution for the linked challenge, depending on chosen ...
10
votes
2answers
646 views
Lean golf: List Game Lv1 (rev_rev)
The title is an homage of the Natural Number Game, which is a nice interactive tutorial into proving certain properties of natural numbers in Lean.
Given that the previous two were slightly too ...
6
votes
3answers
349 views
Tips for golfing in Lean
Lean is a theorem prover and programming language. It's also as of writing the Language of the Month!
What tips do people have for golfing in Lean? As always, tips should be specific to to Lean (e.g....
14
votes
11answers
884 views
Revert Flow Free puzzle
Inspired by Is this Flow Free puzzle trivial? by @Bubbler. Lengthy chunks of this challenge are borrowed from there. This may be one step of a solution for the linked challenge, depending on chosen ...
10
votes
0answers
293 views
Lean golf: Balanced Bracket Sequence
Ungolfed, ugly, horrible proof to help you make progress on this challenge: https://gist.github.com/huynhtrankhanh/dff7036a45073735305caedc891dedf2
A bracket sequence is a string that consists of the ...
15
votes
1answer
540 views
Lean golf: Pascal vs. Fibonacci
The Pascal's triangle and the Fibonacci sequence have an interesting connection:
Source: Math is Fun - Pascal's triangle
Your job is to prove this property in Lean theorem prover (Lean 3 + mathlib). ...
40
votes
17answers
5k views
Recursive Stalin Sort
There is a "sorting" algorithm often called Stalin Sort, where instead of sorting an array, you just remove any items that are out of order. In this challenge, you'll implement part of a ...
21
votes
2answers
2k views
∀ a b. a + b = b + a
This question is a part of the lean LotM.
A ring is a type of structure that takes the rules of addition and multiplication we are familiar with and abstracts them, so we can reason about them. To do ...
54
votes
45answers
7k views
Increment The Time
Every digital clock contains a small creature that has to advance the time every minute [citation needed]. Due to the popularty of digital clocks and the popularity of catching them in the wild, they ...
17
votes
13answers
2k views
The Area of Rectangles
Getting the area covered by a rectangle is really easy; just multiply its height by its width. However in this challenge we will be getting the area covered by multiple rectangles. This is equally ...
15
votes
44answers
3k views
Implement the hyperfactorial
The objective
Given the non-negative integer \$n\$, output the value of the hyperfactorial \$H(n)\$. You don't have to worry about outputs exceeding your language's integer limit.
Background
The ...
13
votes
15answers
1k views
Create a Formatted Multiplication Table
Your task is to create a good multiplication table for others to use. Given an integer \$n\$, generate a multiplication table that displays products up to \$n×n\$. You should start with \$2×2\$ as 1 ...
14
votes
2answers
496 views
Is this Flow Free puzzle trivial?
Background
Flow Free is a series of puzzle games whose objective is to connect all the same-colored pairs of dots on the grid. In this challenge, we consider the original game on a rectangular grid (...
10
votes
5answers
540 views
Khinchin's constant bad estimate [closed]
Inspired by How to write down numbers having an infinity of decimals? Link 🇫🇷
Background
From Wikipedia: for almost all real numbers \$x\$, coefficients \$a_i\$ ...
5
votes
6answers
151 views
"Fold" the array [duplicate]
An example will easily explain this to you. Suppose an array [1,2,3,4,5]
Step 1
1 2 3 4 5
----+----
Step 2
...
10
votes
15answers
2k views
Minimizing flights of stairs climbed
Challenge
Given input as a list/array of natural numbers that each represent the floor of a class a student has to go to, sort the numbers in a way such that the MAD (mean average deviation) number of ...
22
votes
19answers
3k views
Find the longest line
Given a string containing only the characters -, |, + and newline determine the longest ...
16
votes
2answers
521 views
Validate Sudoku on a Mobius Strip
@BeastlyGerbil presents, the world's very first MOBIUS SUDOKU:
Google Sheets version
(The left most square backs onto the right most square, and the middle squares back onto each other. The ends are ...
13
votes
11answers
3k views
Simulate my pill box
I have a small pill box of \$n\$ slots. (Think of it as a linear one like the image below, but not necessarily having 7 slots.)
Each slot has at most one pill. Every day, I take one of two actions: ...
9
votes
9answers
425 views
\$n\$ swaps into a nop
Given \$n, m\ge 1\$. There are \$n\$ balls. Do \$m\$ moves, each choose a ball (maybe also the first one), and exchange with the one currently on the first place. At the end, the order of balls should ...
16
votes
15answers
1k views
Drop down the numbers
This was inspired by Apply gravity to this matrix
Your challenge is to input a matrix with non-negative one-digit integers and drop down the 1's down 1 column, the 2's down 2 columns, the 3's down 3 ...
7
votes
8answers
303 views
Encrypt this Message [duplicate]
Given a permutation of the alphabet and an input string, encrypt the input string by replacing all characters with the one's you've been given.
The capitalization should be kept the same and non-...
14
votes
24answers
1k views
Count occurrences in Pascal's Triangle
Pascal's triangle is a triangular diagram where the values of two numbers added together produce the one below them.
This is the start of it:
...
17
votes
17answers
2k views
Longest Uncommon Substring
For the purposes of this challenge a substring \$B\$ of some string \$A\$ is string such that it can be obtained by removing some number of characters (possibly zero) from the front and back of \$A\$. ...
2
votes
6answers
535 views
Multiplication for geometric algebra
The basis vectors for geometric algebra are
$$(e_0=1), e_1, e_2,\dots,e_n$$
They all square to 1 (we do not consider vectors which square to -1 or zero)
$$e_i \cdot e_i = 1$$
They are associative and ...
15
votes
22answers
1k views
Parentheses Clusters
Write a program that groups a string into parentheses cluster. Each cluster should be balanced.
Examples :
...
1
vote
0answers
160 views
Pythagoras' Golfing Grid [closed]
Recently, I created a binary word search that got me working with grids. It was fun, so I wanted to create some more similar content. Meet Pythagoras' Golfing grid:
Each of ...
8
votes
7answers
885 views
Best response to the Evolution of Trust? - Part 1
Backstory
I was fiddling around with the Evolution of Trust and thought of this.Warning: I recommend you go check it out first before attempting this challenge.
Summary for people who haven’t played
A ...
23
votes
28answers
2k views
17
votes
4answers
892 views
Find the sliced sheet of paper
Context :
Suppose you have a sheet of paper measuring 8 x 10. You want to cut it exactly in half while maintaining its rectangular shape. You can do this in two ...
21
votes
24answers
3k views
Apply gravity to this matrix
This was inspired by this question.
Given an \$m\times n\$ matrix of \$0\$'s and \$1\$'s, apply "gravity" to it. This means to drop down all the \$1\$'s as if they were affected by gravity.
...
7
votes
2answers
313 views
Setting up Al's R session
Al wanted to use my computer to do some simple calculations, so I lent him the use of my R terminal for a bit. He complained though, saying it wasn't set up how he liked it. I said "No problem Al,...
