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Questions tagged [primes]

Primes or prime numbers are numbers which are divisible only by themselves and one, starting with 2, 3, 5, 7, 11.... They are commonly used in encryption and hashing algorithms.

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Subtracting composits from wheel for primes in Haskell

Calculating many remainders for each prime and composite consumes more time. I use a factoring function to find factors of single values. When I use a factoring function to find lists of primes, I ...
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Efficient Prime Number Generator in c++

I am trying to make an efficient prime number calculator. I've seen ones that can go up to close to 1 trillion in right around 4 hours, however I left mine on overnight and didn't get anywhere near ...
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Prime factors and perfect square

I want to convert an integer to a perfect square by multiplying it by some number. That number is the product of all the prime factors of the number which not appear an even number of times. Example ...
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Generate two random primes and find their totient

I am supposed to make a basic RSA encryption/decryption code, where I am only given e. I wrote this code to randomly generate two primes and then find their totient. But the totient is supposed to ...
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Counting primes in a range whose digits are all prime

Codewars Kata: Given integers a and b, count all primes p where a ≤ p < b and the digits of p are all prime. b may be as large as 107. To start with, I hardcoded all valid 1903 primes in \$[1, 10^...
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Rust version of basic functional prime stream - can this be made less clunky?

I'm looking at implementing the basic functional not-quite-Eratosthenes prime stream in Rust. I like to try it when I start learning a language. Here's the bog standard Haskell version: ...
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Work out largest prime factor of a number

I am trying to get better at problem solving, so I am going through challenges on Project Euler. Problem: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of ...
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56 views

Fast Factorisation (Python Implementation)

An algorithm for finding prime factors of a number given a list of all primes up to the square root of the number. It's worst case time complexity is \$O(n^{1/2})\$, the best case would be \$O(\log(n))...
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The next prime number in Python

I have written a solution to a DM::OJ exercise to find the next Prime Number after a given number (input). I'm seeking to optimize it so that it will run for any number up to ...
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Kattis prime reduction challenge

I am solving the Prime Reduction challenge on Kattis. Consider the following process, which we’ll call prime reduction. Given an input x: if x is prime, print x and stop factor x into its ...
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110 views

Faster Sieve of Eratosthenes

This is an implementation of the Sieve of Eratosthenes : It takes advantages of the fact that all primes from 5 and above can be written as 6X-1 or ...
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Euler Project #3 Largest prime factor timeout

I have been recently trying my hands on Euler's Project through HackerRank and got stuck with project #3 where you have to find the Largest Prime Factor. Question: The prime factors of 13195 are 5, 7,...
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Find primes that are also primes when its digits are rotated

The program below is meant to find all of the fare prime numbers under a user specified value. A fare prime being a number that when its digits are rotated, each combination makes a prime number. An ...
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Project Euler #7: Nth prime number

I was solving Project Euler #7 on Hackerrank but for two cases, execution time is more than 2 sec. Can you help with optimizing? I'm new to programming. ...
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Naïve Prime Factorization in Clojure Pt. 2

After my last review request, I decided to try and make a "tree" visualization, and thought that I could benefit from making find-prime-factors lazily produce prime ...
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Naïve Prime Factorization in Clojure

I saw a question about prime factorization on Stack Overflow and realized I had never attempted it before. This was what I ended up with after some playing around and tweaking. I'd like improvements ...
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Find “prime polynomials” for a user's given prime, bounds, and degree

Very amateur programmer and first-time poster here. The program I wrote asks the user for a prime number, a lower and upper bound, and a degree (all of these are integers). I want to generate a list ...
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Finding all prime factors of a number in C# [closed]

I recently wrote a function to find all prime factors of a number and I'd like to know how to improve it. I'm particularly interested in how I can redesign anything to make it more efficient, mainly ...
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A Rust crate with both `main.rs` and `lib.rs` performing primality checking

Introduction I decided to get my feet wet in Rust by going ahead an implementing a full crate with the tests, documentation, and all other accompanying stuff. This is a toy implementation of a ...
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Prime engine: generation, primality, factorization

I've just written my first C# class, so I'm looking for some feedback before I go and write more code. The goal of the code is to provide a Singleton-like class to deal with common operations on the ...
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188 views

Prime factorization in Python

Beginner programmer here. What can I improve in my code? Are there things I'm doing wrong or are there easier ways of doing what I did? ...
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Testing a probabilistic prime-testing algorithm that may fail

I have implemented Pollard's Rho algorithm in Java. Due to the nature of it there is a small chance for it to fail (have not seen it happening yet). Since I do not ...
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Generation of products of power

Given positive integers a,b,c and limit, I want to generate all products having the form $$p^aq^br^c \leq limit$$ less than limit (where p,q,r are distinct primes). a,b and c are not necessary ...
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Euler Problem 7 (finding the 10001st prime) in Powershell

I am having issue making this code more efficient. The problem to be solved is as follows: By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. ...
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Project Euler Problem 37 in Python

Project Euler Problem 37 asks: The number 3797 has an interesting property. Being prime itself, it is possible to continuously remove digits from left to right, and remain prime at each stage: 3797,...
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Display a number as a product of its prime factors

Task: Link to original problem :https://www.spoj.com/problems/FACTCG2/ The task in this problem is to write a number in a multiplication of prime numbers separated by “...
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Finding primes from random integers

I was hoping I could get some help making my code more efficient. I'm a math major taking an Intro to Programming class, and I was asked to write a C program that generates: A text file named ...
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113 views

Program that finds prime numbers in a specific range

I'm kinda new to programming, and as a solution to an exercise, I made a program to find prime numbers in a range. It runs just right for small ranges of numbers, but for this exercise we are given a ...
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Prime factorization program

Compute the prime factors of a given natural number. A prime number is only evenly divisible by itself and 1. Note that 1 is not a prime number. My solution will catch every prime up to and including ...
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112 views

Sieve of Eratosthenes in Rust

This is a relatively simple implementation of the Sieve of Eratosthenes in Rust. The main objective is to find the \$n\$th prime quickly when \$n\$ might grow to huge numbers. ...
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Checking if a number is prime in NASM Win64 Assembly

I'm just learning Assembly. This program is a simple attempt to determine if a given number is prime or not. Any advice and all topical comments on code optimization and conventions is appreciated! ...
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Prime number generation - SPOJ

This is a program to generate prime numbers for a given range. The sieve of Eratosthenes algorithm was implemented, but still the SPOJ says time limit exceeded. Where can some optimizations be made? ...
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C++/STL Prime tuples (twin, cousin, sexy) up to the given limit

As I'm mastering STL I wrote a solution for generating all the prime tuples of the form (p1,p2) where "twin" means p2-p1=2, "...
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For pairs of elements, count the ones whose XOR value is a sum of two primes [closed]

An array is given with 'n' Values ( n <= 10^5 ) ; we have to calculate xor of each pair of elements and count those pairs whose xor can be written as sum of two prime numbers with the same parity(...
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Calculate divisors using prime factorization

For learning purpouses I wrote a class that is supposed to find all divisors for a given integer. My class makes use of primes and prime factorization to speed things up a bit. What can I improve in ...
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Largest prime factor function

I have written a function which finds the largest prime factor of some number. This function works but the problem is that it is too slow. For instance, when I enter 600851475143 as a parameter, the ...
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alternating Fibonacci and prime series

The task is to print the following series 1 2 1 3 2 5 3 7... The elements at odd positions are Fibonacci series terms and the elements at even positions are ...
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Prime pair set finder (Project Euler problem 60)

I made a code that can find the prime sets: The primes 3, 7, 109, and 673, are quite remarkable. By taking any two primes and concatenating them in any order the result will always be prime. For ...
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Are numbers prime multithreading

I'm trying to learn some multithreading and this seems like a good example, want to apply this to frustum culling later. The goal is to find prime numbers in randomly generated vector of numbers. ...
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Printing all the factors as well as the prime factors of a given number using Python 2.7.x

Okay here is my maiden attempt at programming using Python 2.7. I need help or feedback on this code: How do I know about the processing cycles this program consumes? How do I implement this idea ...
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Printing factors and prime factors of a number

I am a 46 year young newbie trying to learn programming for fun and adventure. I do this in my free time. Some very nice gentlemen on stackoverflow have sent me here. I wish that someone could review ...
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Spoj-Prime Generator

Question- Generate all prime numbers between two given numbers. https://www.spoj.com/problems/PRIME1/ My attempt- I used segmented sieve method. ...
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534 views

Euler problem 3: largest prime factor of the number

I have been trying to learn Python and just solved Euler Problem 3: The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ? I am looking ...
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1answer
137 views

Sieve of Eratosthenes in Python

This is yet another take in Python for the infamous Sieve of Eratosthenes. I am a beginner in Python so any criticism is highly appreciated. ...
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Calculating primes until a user-given value

I am new to C# programming. I wrote a little program in C# to calculate all primes until a user-given value. Ignoring the lack of computing power I wrote this program to handle theoretically very huge ...
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Show all primes in go

I'm trying to go through Adrian simple programming tasks; Elementary task 8 It's basically asking for an infinite loop to print every prime number as it finds it. Are there too many ...
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296 views

Prime number sieve in Standard ML

As practice, I have written a prime number sieve in Standard ML. It works in a pretty straightforward way: The list of known primes starts with just 2. Starting with 3, check whether each odd ...
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Python 3: Why is my prime sieve so slow?

I've implemented the sieve of Eratosthenes in Python 3 as follows: ...
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129 views

Project Euler: Find 10.001st prime

I have just started learning C# and decided to do some problems from Project Euler. I wrote a code to find 10 001st prime and I thought it would be cool optimize it to make it as fast as possible. How ...