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Produce a secure block cipher round function (1 bit round key; 7 bit message) [closed]

We need to produce a block cipher round function with a 1 bit round key size and a 7 bit message size with the highest level of cryptographic security according to our measure of security. ...
Joseph Van Name's user avatar
9 votes
8 answers
691 views

Produce the shortest suffix for an (almost) arbitrary string

I encountered some silly code from a game and I figured this would actually turn into a fun golfing problem, so: Given any ASCII string in the limited char range specified below. Append as few ...
Olipro's user avatar
  • 199
12 votes
6 answers
2k views

Sine using square root [closed]

Given input \$x \in \left\{0,3,6,...,90\right\}\$, output \$\sin\left(x°\right)\$ using integer and \$+ - \times \div ( ) \sqrt{\cdot}\$(square root), e.g. \$\sin(45°)=\sqrt{1\div 2}\$. Flexible ...
l4m2's user avatar
  • 24.8k
17 votes
14 answers
2k views

Finding the power sandwich version 2

Introduction This question is inspired by this great question. Challenge Given a number \$N>0\$, output the largest integer \$a^b\$ that is smaller or equal to \$N\$, and the smallest integer \$c^d\...
Dmitry Kamenetsky's user avatar
15 votes
16 answers
2k views

Finding the power sandwich

Introduction Finding the closest power to a number is a common enough problem. But what if you need both the next-highest and next-lowest power? In this challenge you must find the closest powers to a ...
calvenable's user avatar
10 votes
6 answers
481 views

Hermite interpolation

We already have a challenge for polynomial interpolation: given a list of points, output the coefficients of the polynomial that passes through them. Hermite interpolation is a generalization of ...
alephalpha's user avatar
  • 48.6k
14 votes
10 answers
1k views

Expected number of rounds for this labeling scheme

Task Here is an interesting math problem: Let's say that there are \$n\$ indistinguishable unlabeled objects in a bin. For every "round", pull \$k\$ objects randomly out of the bin with ...
Aiden Chow's user avatar
  • 13.7k
10 votes
5 answers
548 views

Write a variadic fixed point combinator

A fixed-point combinator is a higher order function \$\mathrm{fix}\$ that returns the fixed point of its argument function. If the function \$f\$ has one or more fixed points, then $$\mathrm{fix} f=f(\...
Legendary Wizard's user avatar
3 votes
2 answers
346 views

Visualise the Euclidean GCD [duplicate]

The Euclidean GCD Algorithm is an algorithm that efficiently computes the GCD of two positive integers, by repeatedly subtracting the smaller number from the larger number until they become equal. It ...
emanresu A's user avatar
16 votes
18 answers
2k views

Divisor chain counts (1 3 3 7 ...)

The divisors of a natural number form a poset under the relation of "a divides b?", \$a | b\$. This challenge is to produce the number, \$C\$, of non-empty chains of such posets for natural ...
Jonathan Allan's user avatar
9 votes
5 answers
2k views

Random factorized numbers

Input The code should take an integer \$n\$ between 1 and 1000. Output The code should output positive integers with \$n\$ bits. Accompanying each integer should be its full factorization. Each ...
Simd's user avatar
  • 3,088
9 votes
9 answers
2k views

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 ...
Wheat Wizard's user avatar
  • 98.9k
22 votes
8 answers
2k 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, ...
emanresu A's user avatar
13 votes
11 answers
5k 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: ...
emanresu A's user avatar
10 votes
7 answers
776 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, ...
Anm's user avatar
  • 203
9 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 ...
Joseph's user avatar
  • 115
6 votes
4 answers
586 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 ...
Command Master's user avatar
11 votes
26 answers
2k 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. ...
ATaco's user avatar
  • 10.9k
24 votes
23 answers
4k 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\$ ...
xnor's user avatar
  • 145k
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 (...
math scat's user avatar
  • 9,408
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: ...
Philippos's user avatar
  • 2,590
20 votes
11 answers
2k 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 +...
Command Master's user avatar
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 ...
ATaco's user avatar
  • 10.9k
23 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 \...
MTN's user avatar
  • 783
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-...
ATaco's user avatar
  • 10.9k
10 votes
6 answers
980 views

Calculate the Distance to a Line Segment

The Challenge Given two vertexes and a point calculate the distance to the line segment defined by those points. This can be calculated with the following psudocode ...
ATaco's user avatar
  • 10.9k
12 votes
4 answers
514 views

Zeckendorf to F(4k+2) representation

Background Fibonacci numbers are defined as follows: $$ F_0 = 0, F_1 = 1, F_n = F_{n-1} + F_{n-2} $$ The Zeckendorf representation is a representation of positive integers as a sum of one or more non-...
Bubbler's user avatar
  • 77.2k
20 votes
9 answers
2k views

Cutting a Circular Pizza Vertically

Most people would cut circular pizzas into circular sectors to divide them up evenly, but it's also possible to divide them evenly by cutting them vertically like so, where each piece has the same ...
Yousername's user avatar
  • 4,040
16 votes
15 answers
1k views

Find separating sets

Two points pand q in a topological space can be separated if there are open sets U and ...
bsoelch's user avatar
  • 6,035
21 votes
18 answers
2k views

Is this set laminar?

A family of sets is called laminar if for any two sets \$A\$ and \$B\$ in the family one of the following is true: \$ A \subseteq B \$ \$ A \supseteq B \$ \$ A \cap B = \emptyset \$ Or less ...
bsoelch's user avatar
  • 6,035
9 votes
5 answers
913 views

Compute the logarithm of a matrix

There have already been challenges about computing the exponential of a matrix , as well as computing the natural logarithm of a number. This challenge is about finding the (natural) logarithm of ...
bsoelch's user avatar
  • 6,035
15 votes
7 answers
1k views

Solve quadratic equations when 1+1=0

There already have been multiple challenges about carryless multiplication, this challenge will work with the same calculation rules. You task is given a quadratic polynomial ...
bsoelch's user avatar
  • 6,035
17 votes
22 answers
2k views

Compute this fractal matrix

The unique-disjointness matrix ( UDISJ(n) ) is a matrix on all pairs of subsets of {1...,n} with entries $$ U_{(A,B)}=\begin{cases} 0, ~ if ~ |A\cap B|=1\\ 1, ~ ...
bsoelch's user avatar
  • 6,035
14 votes
14 answers
2k views

Print all Polynomials

The set of all polynomials with integer coefficients is countable. This means that there is a sequence that contains each polynomial with integer coefficients exactly once. Your goal is it to write a ...
bsoelch's user avatar
  • 6,035
11 votes
22 answers
2k views

Generate the Crystal Maze™ time matrix

Behold! The Crystal Maze™ Time Matrix! ...
AJFaraday's user avatar
  • 11.8k
19 votes
10 answers
3k views

Numbers that can be negated by reading backwards

Balanced ternary is a modified version of ternary (base 3), using the three digits 1,0 and -1...
bsoelch's user avatar
  • 6,035
24 votes
40 answers
2k views

Diagonalize a vector

Diagonalize a vector into a matrix. Input A vector, list, array, etc. of integers \$\mathbf{v}\$ of length \$n\$. Output A \$n \times n\$ matrix, 2D array, etc. \$A\$ such that for each element \$a_i \...
bigyihsuan's user avatar
-1 votes
1 answer
77 views

Find the sum of primes [duplicate]

Given a number x, find the sum of all primes up to that number. The input will always be a positive number, bigger than 2. An upper limit isn't defined, so data types can be ignored. Use whichever you ...
S-Flavius's user avatar
  • 457
14 votes
19 answers
3k views

Vanilla Natural Logarithm Challenge

There is a challenge for multiplying two numbers so I guess this counts too Given as input a positive real number n compute its natural logarithm. Your answer ...
mousetail's user avatar
  • 12.7k
26 votes
41 answers
3k views

Sum of a range of a sum of a range of a sum of a range of a sum of a range of a sum of

Inspired by the fact that a few related challenges to this could be answered by Vyxal in 0 Bytes using a special flag combination. Given only one input integer \$n\$, calculate \$f(n,n)\$ where $$ f(x,...
The Empty String Photographer's user avatar
17 votes
18 answers
2k views

XOR of independent Bernoulli variables

In probability theory, a Bernoulli variable is a random variable which has a single parameter \$p\$, and is equal to 1 with probability \$p\$, and 0 with probability \$1-p\$. In this challenge, there ...
Command Master's user avatar
50 votes
40 answers
3k views

Last odd digit of power of 2

Task Given \$n\$, output position of the last odd digit in the decimal representation of \$2^n\$ (counting from the end). Rules There are no odd digits for \$n=1,2,3,6,11\$ \$(2, 4, 8, 64, 2048)\$ - ...
pajonk's user avatar
  • 17k
10 votes
40 answers
2k views

Output endless powers of 2 [duplicate]

In any programming language, make a program that outputs infinite subsequent powers of two, starting at any power of two with finite integer exponent. There does not need to be a seperator between ...
Dadsdy's user avatar
  • 2,095
20 votes
19 answers
2k views

Logarithmic Incrementation

In this challenge you will write a function that takes a list (ordered set) containing real numbers (the empty list is an exception, as it has nothing) and calculates $$f(x)=\begin{cases}1 & \text{...
The Empty String Photographer's user avatar
21 votes
7 answers
1k views

How many sorting networks?

Below on the left is a picture of a sorting network that can sort 4 inputs. On the right you can see it sorting the input 3,2,4,1. A sorting network of size ...
AnttiP's user avatar
  • 7,898
14 votes
13 answers
1k views

Resultant of two polynomials

The resultant of two polynomials is a polynomial in their coefficients that is zero if and only if \$p\$ and \$q\$ have a common root. It is a useful tool for eliminating variables from systems of ...
alephalpha's user avatar
  • 48.6k
14 votes
8 answers
1k views

Euclidean distance on projective plane

Motivated by this challenge Background Let we have a square sheet of flexible material. Roughly speaking, we may close it on itself four ways: Here the color marks the edges that connect and the ...
lesobrod's user avatar
  • 3,413
22 votes
11 answers
3k views

How powerful must this e approximation be?

This challenge was inspired by this non-challenge about the natural logarithm base \$e\$ and the following pandigital approximation to \$e\$ appearing on a Math Magic page: $$\left|(1+9^{-4^{7×6}})^{3^...
Parcly Taxel's user avatar
  • 3,845
10 votes
3 answers
332 views

Representing a number as an unordered list of smaller numbers

Suppose we want to encode a large integer \$x\$ as a list of words in such a way that the decoder can recover \$x\$ regardless of the order in which the words are received. Using lists of length \$k\$ ...
Karl's user avatar
  • 621
44 votes
18 answers
3k views

Compare Two Fractions With ASCII Art

Challenge Write a program or function that takes in 4 non-negative integers, A, B, C, and D, that represent two fractions, A/B and C/D, where B and D are non-zero and A <= B and C <= D. Output ...
blaketyro's user avatar
  • 809

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