All Questions
13,821
questions
15
votes
5
answers
243
views
Write a set as a union of ranges
In this challenge, we define a range similarly to Python's range function: A list of positive integers with equal differences between them. For example, ...
- 34.8k
3
votes
1
answer
99
views
Tips for radiation hardening
The aim of this post is to gather all the tips that can often be applied to radiation-hardening challenges.
Please only post answers which can apply to a large number of languages, and one tip per ...
- 7,698
13
votes
4
answers
1k
views
I irradiate your source code, you irradiate your output
Your task is to write a program \$p\$ which outputs a string \$s\$ with the same length as \$p\$, where \$s \neq p\$.
If I remove the \$n\$th byte from your program to get program \$q\$, then either \$...
- 95.6k
7
votes
7
answers
2k
views
Print 100 digits of π
Your challenge is to print any 100 consecutive digits of π. You must give the index at which that subsequence appears. The 3 is not included.
For example, you could print any of the following:
...
- 34.8k
5
votes
9
answers
637
views
Decrypt an Autokey Cipher
The autokey cipher is closely related to the Vigenère cipher (both were invented by Blaise de Vigenère). Decryption involves the encrypted message and the key. For simplicity, let us assume all ...
- 191
10
votes
7
answers
631
views
Longest sequence of Egyptian fractions with n as denominator
Background
From Wikipedia: An Egyptian fraction is the sum of distinct unit fractions. That is, each fraction in the expression has a numerator equal to 1 and a denominator that is a positive integer, ...
- 201
13
votes
9
answers
671
views
Convert a non-negative integer to Barbrack
Barbrack
Your task is to write a program or function that takes a non-negative integer (in decimal or any other convenient base for your language), and output a number in the numbering system Barbrack....
- 285
-1
votes
0
answers
184
views
Add (Some) Combinatorial Games [closed]
Combinatorial game theory is the study of analysing positions in chanceless games like Hackenbush, Nim and Toads and Frogs.
Positions are usually given a number (more specifically, a surreal number), ...
- 145
1
vote
2
answers
520
views
Compute how many are no larger than each item in an array
Input: an array of length \$n\$ containing integers in the range \$0\$ to \$2n\$.
For each integer \$x\$ in the array, compute the number of integers that occur before \$x\$ that are no larger than \$...
- 1,545
4
votes
1
answer
121
views
I reverse the source code, you reverse the source code! [duplicate]
Write a program that outputs its source code in reverse when run, and outputs its source forwards when I reverse the source. If your program is "abcd", when run with no arguments it should ...
- 4,186
13
votes
5
answers
923
views
Print the answer before a given answer
In this challenge, you'll take an answer as input, and print the answer before it. If the answer passed as input is the first answer, print your own submission's source. You'll be passed any answer in ...
- 18.6k
10
votes
12
answers
3k
views
Funny Numbers :D
The task is to calculate the average "funniness" of a given number given the following scoring system:
1 point for each "420" in it
2 points for each "69" in it
3 points ...
- 109
-2
votes
1
answer
68
views
PHP+C polyglot solution to mixed types
Some built-in functions in PHP return mixed types, like file_get_contents that returns both string or ...
- 175
21
votes
11
answers
2k
views
I (rev)?(pal)? the source code, you (rev)?(pal)? the input!
Just because the reverse and palindrome were not too challenging individually :)
Write a program (full program or function) that satisfies the following: given a string input,
the program as-is ...
- 73.2k
20
votes
8
answers
2k
views
Do you win a Numeric Mahjong?
Background
Numeric Mahjong is a hypothetical variation of Japanese Mahjong, played with nonnegative integers instead of Mahjong tiles. Given a list of nonnegative integers, it is a winning hand if it ...
- 73.2k
16
votes
16
answers
1k
views
Reconstruct an array by successive insertions
Given an array of letters in the range 'a' to 'o', compute how to construct the array by successively inserting the letters in alphabetical order. You will always start the insertion with a base array ...
- 1,545
20
votes
10
answers
925
views
Implement Subleq
Subleq is a Turing-complete esolang with only one instruction, SUBLEQ. This instruction takes in three parameters, A, B, and <...
- 6,239
23
votes
19
answers
2k
views
Find the largest sum such that no two elements are touching
Inspired by this (off topic) post
Given an array of numbers, find the largest sum over a subarray not containing two adjacent elements
...
- 4,781
-2
votes
1
answer
183
views
Comparator function in Javascript [closed]
Need to write a JS function compare(a,b) for numbers which return
1 when a > b, 0 when a == b, -1 when a < b.
Also following properties should hold:
compare(NaN, NaN) = 0
NaN is bigger than any ...
- 1
16
votes
10
answers
1k
views
Find the longest permutations of integers from 1..k such that all neighbouring pairs sum to a square
OEIS A090461 details the ‘numbers k for which there exists a permutation of the numbers 1 to k such that the sum of adjacent numbers is a square’. This has also been the subject of Matt Parker’s ...
- 17.1k
6
votes
1
answer
334
views
Self-referencing tuple in python
Goal: create a self-referencing tuple satisfying x == (x,) in any version of Python. Standard libraries, matplotlib, numpy, pandas only.
Answers meeting this extra ...
- 171
15
votes
13
answers
2k
views
Keep jumping till a cycle
Objective
You're on a nonempty list of integers that wraps around. You start at the leftmost entry of the list, and keep jumping to the right to the amount of the integer entry you're at.
Eventually, ...
- 5,143
10
votes
16
answers
1k
views
Numbers with distinct decimal digits
Write a program or function that outputs all positive integers with distinct decimal digits (OEIS: A010784)
Examples:
...
- 4,781
13
votes
12
answers
2k
views
Play a game of memory
Playing the game of memory against a machine is highly unfair, because they play almost as good as small children. So let's make the machine play alone, but in a fair way:
Input: 1...26 pairs of ...
- 680
0
votes
1
answer
110
views
What is the shortest regular expression (REGEX) you can create for file extensions for image formats? [duplicate]
What is the shortest regular expression (REGEX) you can create for file extensions for all of the following image file formats (photographs, paintings, sketches, and drawings)?
...
- 189
5
votes
5
answers
676
views
Count the size of the Levenshtein neighborhood
Input
A binary string \$s\$ of length \$n\$ and a positive integer \$k \leq n\$.
Output
The number of binary strings with Levenshtein distance exactly \$k\$ from the string \$s\$.
Example outputs
Each ...
- 1,545
11
votes
8
answers
841
views
Shortest English prompt to produce LLM falsehood [closed]
Since programming is predicted to become natural linguisized by the unstoppable advances in LLM technology, perhaps we can code golf LLMs themselves.
Produce the shortest question that is not an ...
- 227
6
votes
4
answers
367
views
Sums of Euler's totient function in sublinear time
Related.
Given a number \$n\$, Euler's totient function, \$\varphi(n)\$ is the number of integers up to \$n\$ which are coprime to \$n\$. That is, no number bigger than \$1\$ divides both of them.
For ...
- 7,698
11
votes
26
answers
1k
views
Find the smallest integer multiple of a Decimal
The Challenge
Given a rational number, determine the smallest number which is a positive integer multiple of it. Eg.
...
- 10.2k
3
votes
1
answer
225
views
Sokobunny I (Sokoban, but the boxes are sentient)
Sokobunny 1
You love buns!
You love them so much, that you chased one down a bunburrow. The burrows are like mazes, and YOU WANT TO CATCH THE FLUFFBALLS!!!! However, the buns are smart! You can't ...
- 107
24
votes
22
answers
3k
views
American odds to probabilities
American odds (aka moneyline odds) are numbers like \$+150\$ or \$-400\$ used to express how much a winning bet would pay out. Convert odds to a fair win probability like this:
Positive odds \$+n\$ ...
- 144k
16
votes
6
answers
2k
views
What's my score?
The question score on Stack Exchange is the total number of upvotes minus the total number of downvotes a question receives. However, the reputation gained/lost for every upvote/downvote is different (...
- 7,939
15
votes
3
answers
372
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 ...
- 4,781
23
votes
10
answers
2k
views
How many ways to cut a number into an equation?
Too bad! I had such a beautiful equation, but I lost all my =+-*, so there is nothing left but a chain of digits, looking like a number: ...
- 680
20
votes
12
answers
1k
views
Sums of sum of divisors in sublinear time
Given a number \$n\$, we have its sum of divisors, \$\sigma(n)\ = \sum_{d | n} {d}\$, that is, the sum of all numbers which divide \$n\$ (including \$1\$ and \$n\$). For example, \$\sigma(28) = 1 + 2 +...
- 7,698
24
votes
26
answers
2k
views
Longest Consecutive Sequence
Description
Given a list of positive integers, write the shortest code to find the number count of the longest consecutive sequence of numbers within the list.
Input
A list of positive integers. You ...
- 1,732
1
vote
0
answers
177
views
DP approach gives TLE [closed]
There is a question to basically find the largest sum in an array, such that no two elements are chosen adjacent to each other. The concept is to recursively calculate the sum, while considering and ...
- 11
21
votes
19
answers
2k
views
Simulate Round Robin Scheduling
Alternatively, guess who's doing a course on operating systems
Round Robin scheduling is a way to schedule ready processes in an operating system. Each process in the queue is run for a certain amount ...
- 31.7k
28
votes
9
answers
3k
views
What's my type? Well... Probably
There are a lot™ of pokemon. One of the defining characteristics of pokemon is their type, of which every1 pokemon has up to two types, a primary type and an optional secondary type. There are ...
- 58.8k
4
votes
6
answers
259
views
Pseudo-Quantum Bogosort [closed]
Pseudo-Quantum Bogosort
Quantum Bogosort is as follows:
Quantumly randomise the list, such that there is no way of knowing what order the list is in until it is observed. This will divide the ...
- 1,360
10
votes
13
answers
2k
views
Decimalize a Fraction
Preamble
A common pain-point when working with rational numbers and decimals is how infrequently one can represent their rational number as a clean, non-repeating decimal. Let's solve this by writing ...
- 10.2k
22
votes
14
answers
2k
views
Sum of consecutive nth powers
Related.
Given a positive integer \$n\$, output all integers \$b\$ (such that \$1<b<n-1\$) where \$n\$ can be written as the sum of any number of consecutive powers of \$b\$.
Example:
Let's say \...
- 761
17
votes
27
answers
2k
views
Order by Earliest Lower Digit
Given two strings of digits, determine which string, if any, has the earliest digit which is lower than the other string's digit at the same index.
Do note that this differs from alphabetization, as ...
- 3,257
11
votes
20
answers
4k
views
Add two really big numbers
Preamble
We've already proven we're good at adding two numbers, but many solutions only operate on tiny numbers like 2³²-1, honestly we can do a lot better.
The Challenge
Given two unsigned, non-...
- 10.2k
14
votes
18
answers
2k
views
Golf the fast growing hierarchy
The fast growing hierarchy is a way of categorizing how fast functions are growing,
defined the following way (for finite indices):
\$ f_0(n)=n+1 \$
\$ f_k(n)=f_{k-1}^n(n)\$ with \$f^n\$ meaning ...
- 4,781
18
votes
20
answers
3k
views
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 ...
4
votes
4
answers
520
views
We already have pipes & pattern matching at home! [closed]
Inspired by this tweet where a user stated the following:
it's insane how much code would be cleaned up if JS got pipes and pattern matching
i often do this since it's the best way to make use of TS ...
- 605
8
votes
6
answers
1k
views
Inverse trigonometric functions
There are 3 (commonly used) trigonometric functions sin cos and tan each of these functions ...
- 4,781
6
votes
3
answers
482
views
Pick a random string at a fixed edit distance
I have string \$s\$ of length \$n\$ and some constant integer \$k\$ which is at most \$n\$. Give the fastest algorithm to sample a random string with Levenshtein distance \$k\$ from \$s\$ uniformly.
...
- 1,545
16
votes
5
answers
557
views
Prefix code generator
In this challenge, we consider an encoding from positive integers (up to a limit) to binary sequences. Some examples:
...
- 73.2k