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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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### Sieve of Atkin C#

I don't fully understand how to make the Sieve of Atkin faster than the most ancient sieve. All implementations I found online where slower than the one I made, but still It isn't faster than ...
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### Calculate the first largest factor of 600851475143

ٍProblem description: The prime factors of 13195 are 5, 7, 13 and 29. Largest prime factor 13195 is 29. What is the largest prime factor of the number 600851475143 ? Prime Factor: any of the prime ...
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### CommonPrimeDivisors task from codility [closed]

I'm working on the following task from Codility: A prime is a positive integer X that has exactly two distinct divisors: 1 and X. The first few prime integers are 2, 3, 5, 7, 11 and 13. A prime D is ...
1 vote
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### Count SemiPrimes task from Codility

I'm trying to solve the following exercise from codility: A prime is a positive integer X that has exactly two distinct divisors: 1 and X. The first few prime integers are 2, 3, 5, 7, 11 and 13. A ...
1 vote
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### Clojure Prime Numbers from 1 to 1000

I am a beginner to Clojure and I made a little script that prints out every prime number from 1 to 1000. Let me know if there are any improvements that I can make: ...
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### Find prime numbers

I wanted to create a program that lists all prime numbers to a given upper bound and that will also provide the amount of primes in the set. After many hours of trial and error I was able to solve it. ...
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### Prime number generator in lisp

My implementation is based on the incremental prime sieve described on Wikipedia. I'm relatively new to lisp so I would appreciate any comments on my coding style or on the algorithm. The below code ...
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### calculating all prime numbers up to a given number

This program calculates all prime numbers up to n. However it runs pretty slowly. I was wondering if there was any optimisations I could make. ...
1 vote
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### C code for discovering numbers with interesting/beautiful/symmetric properties

Below is a C code that generates 1000 random positive integers, for each number we check primality, palindromic property, and the square root of the sum of the digits. The purpose is to find/discover ...
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### Factor 999999 numbers as fast as possible

My code finds the prime factorization of numbers, ordering the prime numbers from least to greatest. It prints a list of 999999 prime factorizations (which can be changed if you edit the function call ...
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1 vote
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### MIPS-32 assembly: Determine if n is prime

I'm new to assembly and I'm learning on my own, so I'd appreciate the feedback. My priorities are correctness (on all MIPS-32 with sllv) > speed > readability ...
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### Sieve of Eratosthenes in F#

after looking at the pseudocode for the Sieve of Eratosthenes on wikipedia I tried implementing a similar version using F#. The code runs just fine, that is, it returns all prime numbers up until a ...
163 views

### Prime numbers iterator

I am not familiar with iterators. I am confused with the traits approach and the traditional one. I don't know which one I should use in 2021. I wrote a minimal ...
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### Average prime number from array- Javascript

My mission is to solve this: Write a function that will take an array of numbers, and will return the average of all numbers in the array that are prime number. So far I wrote this: ...
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### Generating prime numbers quickly in rust

I am attempting to re-implement a postponed sieve algorithm for generating prime numbers in Rust. I am able to make a solution that works, but I have to use a couple of ...
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1 vote
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### Improving Project Euler code problem #10

So, I just finished Problem 10 on Project Euler, but it took about 3 to 4 minutes for my output to come out, due to bad coding, I guess, any suggestions on how could I optimize my code? Question The ...
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### My prime number generation program in Python

So I did my own take (I wrote my own algorithm) for generating prime numbers from 1 to 1000. ...
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1 vote
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### A function to find all the primes between two numbers whose reverse is also a prime and doesn't include palindrome, in JS

I am trying to solve a challenge in which I have to write a function that takes in two numbers as arguments and returns an array containing numbers between them which are prime and their reverse is ...
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309 views

### Sieve of Eratosthenes in Vyxal

I'm trying to learn the golfing language Vyxal because I occasionally contribute to it, and I'm slightly ashamed I can't even use it. To do this, I started with implementing the Sieve of Eratosthenes ...
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### Python – return list (or not?) of prime numbers between two numbers

I'm trying to learn how to write code well in Python. I've been tinkering with a function that will return a list of all prime numbers between the two parameters. This is the best I could come up with ...
1 vote
169 views

### Count prime numbers whose rotations are all prime

This code solves Project Euler problem 35: The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. There are thirteen such primes ...
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1 vote
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### Find the 10001st prime number

Project Euler 7: What is the 10 001st prime number? I currently have this code: ...
1 vote
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### Python Prime Search Slower Optimization

I have these 2 version of code. Both are looking for all primes under a certain ceiling value. The first is testing against the set of all odd numbers. The second in testing against the set of all 6k-...
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### Optimize TI-BASIC Prime Numbers Finder

I wrote a program to find all the prime numbers up to N on my TI-84, however, it is quite slow for any number above, like, 50. Are there any ways to optimize my ...
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### Function returning a vec with prime factors of number

See code below and my comment with questions: ...
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Exercise: Write a prime number-test isPrime(num: Int), which for integer m >= 2 checks, if the integer is a prime number or not. My solution: ...
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### Primality Test Refactoring

I devised a new primality test isPrimeNumber() below which determines if 1000000007 is prime. It works fine but the code looks unprofessional in my opinion. Is there any way to refactor it to make it ...
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### Why is this Segmented Prime Sieve so fast?

The idea of a prime sieve is fascinating - but it has to be segmented to increase the locality of the code if you want it to be fast. Walish's segmented_sieve.cpp (see below)showed me that it works - ...
380 views

### Calculate all the prime numbers between two given numbers

I've made an application that calculates all the prime numbers between two given numbers and prints then into a .txt document... anything I can improve? ...
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### Is this an efficient/correct way to get largest Prime factor?

Is this an efficient way to get the largest prime factor of a given number? Other solutions I found involved nested algorithms. ...
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### Prime number sequence supporting repeated iteration

I'm a long-time Java programmer, but recently I decided to give Kotlin a try. So far, I'm loving the language features, it feels much more expressive than what I'm used to. As practice, I wrote this ...
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### Performance issue regarding Project Euler #60 in Scheme

I solved Project Euler #60: 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 example, taking 7 ...
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### Why is my Sieve of Eratosthenes using generators so slow

This is my prime sieve based on the Sieve of Eratosthenes. ...
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### C: Sieve of Eratosthenes and next twin prime

I am wondering if I can get some feedback for my implementation of "Sieve of Eratosthenes" and twin prime. I followed this pseudocode. Few notes: I added ...
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### Factorize All Numbers Up to a Given Number

this post is sort of a continuation of my answer on the following question: Fast Algorithm to Factorize All Numbers Up to a Given Number. As this post explains - We need to factorize all the numbers ...
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### Project Euler 50: Consecutive prime sum

I just finished solving Project Euler's 50th problem, but it's awfully slow. I'd like to hear your thoughts on my code's efficiency and practices. Problem Statement The prime 41, can be written as the ...
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### Finding the first pair of prime numbers that have some specified difference

I tried printing the first pair of prime number in between a list of numbers with a particular difference. But my run time is still too high (for large range of numbers). I want to reduce the run time ...
313 views

### Add a number to a number to be prime number in python

The program is to get the nearest prime number to a number while adding a number. I solved the problem but I wish to optimize the code. ...
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1 vote
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### Calculating primes: Could this be any faster?

I've ported a prime-number calculation program from primes.pyx to C++ for benchmark purpose. Since I wrote it in C++, I thought that my program would be faster than the original. However, mine took 25....
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### Prime power mathematical problem in Python

I have a mathematical problem about prime power. A number $x$ can be considered a prime power if $x = p^k$ where $p$ is a prime and $k$ is a non-negative integer. For example, $81$ is a ...
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### Faster way to check if number has factor of different primes than given list of primes

im trying to get the factor prime number(s) for given number if its different than the primes that i have in a list. The number have to: dividable with any of the primes in the list should not have ...
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### Hackerrank problem -"Another Prime Problem"

I came across this issue in the problem titled: Another Prime Problem. Here's my solution with JavaScript which passed test case-1, but for other test cases it led to timeout. ...
1 vote
315 views

### Python prime finder

I wanted to try and learn multi-threading, so I thought it would be good to make a small program normally first and make it multi-threaded, so I made this prime finder. ...
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1 vote
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### "Sum by factors" algorithm improvement

I was working on a code challenge with the following description: Given an array of positive or negative integers I= [i1,..,in] you have to produce a sorted array ...
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### Finding consecutive primes matching p, p + 4, p + 6, p + 10, p + 12, p + 16

Someone asked about this question on the main StackOverflow. The full question is: Given a value N, find p such that all of ...
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### Rate my first python prime checker

I'm new to programming; I started about a week ago and started learning python. Currently, I only know some basic arithmetic operations in addition to some basic knowledge about lists, dictionaries, ...
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