# Tagged Questions

The winner of a fastest-code challenge is determined by the runtime performance of the submissions. For fairness, all submissions should be benchmarked on the same machine, which usually means all submissions have to be tested by the host of the challenge. For scoring by asymptotic time complexity, ...

0answers
71 views

### Help the poor Cryptographers - DLP Edition

Introduction and Motivation I'm mainly active on Cryptography.SE and as such have already stumbled across the question: "How the hell am I supposed tools like cado-nfs to do stuff!?". They are super-...
3answers
194 views

### The fastest square root calculator [closed]

Write a program which outputs the square root of a given number in the shortest time possible. Rules It may not use any builtins or powering with numbers between 0 and 1. Input format as a ...
2answers
1k views

### Compute the maximum number of runs possible for as large a string as possible

[This question is a follow up to Compute the runs of a string ] A period p of a string w is any positive integer p such that w[i]=w[i+p] whenever both sides of this equation are defined. Let per(...
3answers
331 views

### Find all the Solutions to this Number Puzzle in the Shortest Time Possible

History My company sends out a weekly newsletter to everyone within the company. Included in these newsletters is a riddle, along with a shoutout to whomever in the company was the first to email/...
3answers
630 views

### Quickly express a number with only 0-9 and the four operations, plus one more extra

Explanation Befunge is a two-dimensional program that uses stacks. That means, to do 5 + 6, you write 56+, meaning: 56+ 5 push 5 into stack 6 push 6 into stack + pop the first two items in ...
2answers
1k views

### Approximating a special case of the Riemann Theta function

This challenge is to write fast code that can perform a computationally difficult infinite sum. Input An n by n matrix P with integer entries that are smaller than 100 in absolute value. When ...
2answers
373 views

### Tic-tac-toe with only crosses as quick as possible

As per Luke's request and Peter Taylor's addition to this challenge. Introduction Everyone knows the game tic-tac-toe, but in this challenge, we are going to introduce a little twist. We are only ...
1answer
324 views

### Find the longest path, avoiding obstacles in a 2D plane

The Scenario You are given a matrix of size m x n (width x height) with m*n spots where there are a few obstacles. Spots with obstacles are marked as 1, and those without are marked as 0. You can ...
5answers
279 views

### Reproportioning a population by adding fixed sized groups

Introduction Say you have a population of people. This population is made up of 100 Alices and 25 Bobs. So, 80% of the population are Alices and 20% are Bobs. We want to change the proportional ...
13answers
2k views

### Calculate the number of primes up to n

π(n) is the number of primes less than or equal to n. Input: a natural number, n. Output: π(n). Scoring: This is a fastest-code challenge. Score will be the sum of times for the score cases. I ...
4answers
437 views

### Counting orthogonal circulant matrices

Two rows of a matrix are orthogonal if their inner product equals zero. Call a matrix with all rows pairwise orthogonal an orthogonal matrix. A circulant matrix is one where each row vector is rotated ...
1answer
216 views

### Set Theoretic Arithmetic (+ and *) [closed]

Set Theoretic Arithmetic Premise There have been a couple challenges already that involve multiplying without the multiplication operator ( here and here ) and this challenge is in the same vein (...
0answers
306 views

### GOLF CPU - Implement Arbitrary Precision Integer Division

This question was inspired this question and @orlp's comment and a lot of the explanation was copied from there. Write a GOLF assembly program that given two arbitrary size decimal integers a, and b ...
2answers
573 views

### Fastest Longest Common Subsequence Finder

Your task is to solve the Longest Common Subsequence problem for n strings of length 1000. A valid solution to the LCS problem for two or more strings S1, … Sn is any string T of maximal ...
3answers
358 views

### Integral triangles and integral medians

Consider a triangle ABC where each side has integer length (an integral triangle). Define a median of ABC to be a line segment from a vertex to the midpoint of the opposing side. In the figure below, ...
12answers
2k views

### Sum of smallest prime factors

SF(n) is a function which computes the smallest prime factor for a given number n. We'll call T(N) the sum of every SF(n) with 2 <= n <= N. T(1) = 0 (the sum is over 0 summands) T(2) = 2 (2 ...
7answers
972 views

### Find the maximum determinant for each size Toeplitz matrix

For a fixed n, consider the n by n Toeplitz matrices with entries which are either 0 or 1. The aim is to find maximum determinant over all such Toeplitz matrices. Task For each n from 1 upwards, ...
2answers
226 views

### The GOLF CPU Golfing Challenge: Sides of a Cuboid

This challenge is the second of a series of fastest-code problems that should be written in the GOLF CPU. You can find the first here For this problem, you are given the volume of a cuboid (A ...
2answers
459 views

### The GOLF CPU Golfing Challenge: Prime Partitions

This challenge is the first of a series of fastest-code problems that should be written in the GOLF CPU. You can find the next one here A partition of a number, N, is a list of numbers that add up ...
1answer
554 views

### Snakes and Ladders probability of winning

(This is my first Q here, and I don't know much about code golfing.) Your aim is to predict the winner of an ongoing Snakes and Ladders game. INPUT A single number (2-1000) indicating the number ...
2answers
218 views

### Solve the Diophantine Pell equation

Given a natural number c as input, our task is finding the fastest way to calculate one -atleast- availabe integer solution (a,b) of pell equation c=a²-b². Rules Built-in functions and loopholes ...
4answers
471 views

### Too many pawns on a chess board

Given an integer 2n, find the number of possible ways in which 2n^2 black pawns and 2n^2 white pawns can be arranged on a 2n by 2n chess board such that no pawn attack another. A black pawn can ...
3answers
549 views

### Covering Array Validator

A covering array is an N by k array in which each element is one of {0, 1, ..., v-1} (so v symbols in total), and for any t columns chosen (so an N x t array) contains all possible v^t tuples at least ...
1answer
417 views

### Compute 30000 Digits of Pi (π), as Fast as Possible [duplicate]

Compute 30000 digits of the mathematical constant π, with the fastest code. Implement in any computer programming language that I can run in my 64 bit Linux machine. You should provide your compiler ...
2answers
723 views

### Probabilities - how high can you go?

I previously asked a question for how to compute a probability quickly and accurately. However, evidently it was too easy as a closed form solution was given! Here is a more difficult version. This ...
5answers
938 views

### Calculate a probability exactly and quickly

[This is a partner question to Calculate a probability exactly ] This task is about writing code to compute a probability exactly and quickly. The output should be a precise probability written as a ...
2answers
997 views

### Extending OEIS: Counting Diamond Tilings

I promise, this will be my last challenge about diamong tilings (for a while, anyway). On the bright side, this challenge doesn't have anything to do with ASCII art, and is not a code golf either, so ...
3answers
516 views

### Supersonic domino tilings

Task Write a program that reads three integers m, n either from STDIN or as command-line arguments, prints all possible tilings of a rectangle of dimensions m × n by 2 × 1 and 1 × 2 dominos and ...
0answers
36 views

### Searching for a sum [duplicate]

In this challenge you will take two inputs One input will be a string of numbers of any length which you will put into an array/table/whatever you call it in your language Ex: 10 10 145 20 53 102 20 ...
4answers
760 views

### Magic Sequences of length n

A magic sequence is a sequence of non-negative integers x[0..n-1] such that there are exactly x[i] instances of i For instance, 6,2,1,0,0,0,1,0,0,0 is a magic sequence since there are 6 0's, 2 1’s, ...
3answers
341 views

### Count balanced binary strings matching any of a set of masks

A binary string is a string which contains only characters drawn from 01. A balanced binary string is a binary string which contains exactly as many 0​s as 1​s. You are given a positive ...
4answers
461 views

### Testing if a number is a square

Write a GOLF assembly program that given a 64-bit unsigned integer in register n puts a non-zero value into register s if n is a square, otherwise 0 into s. Your GOLF binary (after assembling) must ...
3answers
672 views

### Factoring a 64-bit integer

Write a GOLF assembly program that reads an integer from stdin (followed by a trailing newline), and outputs its prime factors seperated by newlines, followed by a trailing newline on stdout. The ...
3answers
570 views

### Count the number of Hankelable matrices

Background A binary Hankel matrix is a matrix with constant skew-diagonals (positive sloping diagonals) containing only 0s and 1s. E.g. a 5x5 binary Hankel matrix looks like a b c d e b c d e f c d ...
1answer
291 views

### Constructing an Orthogonal-Diagonal Greco-Latin Square

Consider a grid of NxN unique elements. Each element has a letter (from A to the Nth letter, inclusive) and a number (from 1 to N, inclusive). Hence, each number/letter pair is in the grid exactly ...
3answers
800 views

### Finding all-but-one matches

This challenge is about writing code to solve the following problem. Given two strings A and B, your code should output the start and end indices of a substring of A with the following properties. ...
7answers
470 views

### Fastest array-by-array nearest neighbour search

Intro - Nearest neighbour comparison between two arrays is something that can be done very efficiently when only 1 variable per array is involved, because it can be done by sorting and then performing ...
2answers
771 views

### Coding a recursive function for highest possible input

Challenge You are given the following function:- which is the same as:- with the base cases q(r, b, L) = 1 whenever r ≤ L, q(r, 0, L) = 0, if r > L and q(r, 0, L) = 1, if r ≤ L. Your task is to ...
2answers
399 views

### Forming Polyominoes with a Chain of Rods

Background Consider a (closed) chain of rods, each of which has integer length. How many distinct hole-free polyominoes can you form with a given chain? Or in other words, how many different non-self-...
2answers
140 views

### Magical Squares [closed]

A perfect square is a number that is the square of an integer. However, let's define something called a Magical Square, which is a perfect square with the following restriction: The perfect square ...
1answer
276 views

### Chotchkies Restaurant [duplicate]

Because there isn't enough xkcd on PPCG... Challenge The challenge is the same as above - given a menu and a total price, you need to find what the customer ordered. The menu will be supplied as ...
3answers
779 views

### Be an Epidemiologist!

Challenge You must create a simple model of how disease spreads around a group of people. Rules and Requirements The model must be a 1000 by 1000 2D array with each element being a different person....
6answers
464 views

### False Positives on an Integer Lattice

Leaderboard User Language Score ========================================= Ell C++11 293,619,555 feersum C++11 100,993,667 Ell C++...
8answers
889 views

### Digit sum of central binomial coefficients

The task is simply to see how much faster you can calculate n choose n/2 (for even n) than the builtin function in python. Of course for large n this is a rather large number so rather than output ...
3answers
1k views

### Another Euler Brick in the Wall

A Euler Brick is a cuboid where the length of all the edges are integers and all of the diagonals of the faces are integers as well. All sides must also be different. Your program has to find as ...
3answers
771 views

### The distance between circles

Imagine you are given two lists of numbers which are to be interpreted as points on a circle of circumference 1000. Let us say circleA = [10, 24, 44, 175, 321, 579, 618, 841, 871, 979] circleB = [...
2answers
572 views

### 2nd byte bias of RC4

Short version RC4, designed in 1987, is one of the most famous stream ciphers. This question asks you to practically demonstrate its 2nd byte bias (for a theoretical proof, see section 3.2 of this ...
1answer
541 views

### 'Number' Crunching Benchmark

I just want to do some benchmarking of different programming languages. So here is a tip: You can use as many characters as you want. In the end there is only the time your program needed. So, here ...
0answers
113 views

### Write program which finds shortest expression for number [duplicate]

Write program which finds shortest expression for big integer. Expression may consist of + - * / ^ ! ( ) operations. ! stands for factorial, ^ - exponentiation, / - rational division. Number itself ...
0answers
278 views

### Write a FAST word equation solver [duplicate]

This question is similar to Write a word equation solver by David Frank but different in three important ways: (1) David asked for just the first solution found, and I am asking for all the solutions. ...