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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Project Euler Problem 35: counting circular primes below 1 million
Project Euler Problem 35 asks:
The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.
How many circular primes are there ...
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1answer
50 views
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1answer
71 views
Largest prime factor of a given number
I'm solving Problem 3 in Project Euler:
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143?
Most answers I found made use of array to ...
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3answers
136 views
Prime factoring function using recursion
As a programming exercise, I decided to make a prime factoring function using recursion:
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2answers
56 views
Infinite prime generator
This code acts as an infinite generator of prime numbers.
As new prime numbers are found, they are added to a set. Then, a number x is found to be prime if none of the numbers in the prime set are ...
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2answers
198 views
Yet Another, Another Prime Generator
Yes, I realize there are many, many, many, many, many, prime generators on the Code Review SE. However, I have been unable to find any using this method for generating primes inside a vector, so I ...
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0answers
12 views
Finding the largest p-adic order of a given integer [closed]
I need to find the highest P-adic order - that is the largest power among the powers of primes in the prime factorization of an integer - of large integers .
The only - and naive - approach I ...
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0answers
25 views
Mersenne Prime Checker using Lucas-Lehmer Formula
Previously I created a C# script that used trial division to check to see whether or not certain Mersenne numbers were prime. Since these numbers are so big, I employed some math shortcuts to reduce ...
12
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2answers
3k views
Project Euler #10 in C++ (sum of all primes below two million)
Project Euler Problem 10 asks for the sum of all the primes below two million.
I'm creating a list of primes and keep checking any new number for divisibility with only prime numbers. I thought it ...
3
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2answers
162 views
Mersenne Primes Generator in C#
I've made a program in C# that generates Mersenne numbers starting from the current largest known Mersenne prime. It then calculates the modulo between those numbers and smaller ones starting from 3 ...
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0answers
48 views
Custom Sieve of Eratosthenes in C++
I'm trying to improve my code to find all the prime numbers within a set range as fast as possible, and I am trying to make it even faster. On my github page here, I have some optimization settings ...
2
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1answer
78 views
List of all prime factors of a number, including repeats
This code will return a list of the prime factors of n, and the prime factors are repeated so that the product of the list is equal to n.
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2answers
139 views
Sieving for prime numbers
I wanted to implement the Sieve of Erathosthenes up to int.MaxValue in C#. No object is allowed to exceed 2Gb so you can't allocate a ...
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4answers
167 views
Calculate prime numbers
This is a program to calculate the largest prime number. Are there any possible improvements in style/speed/accuracy?
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6answers
165 views
Project Euler #3 in C# - largest prime factor
I just started doing the Project Euler challenges and right now I'm on Challenge #3 - The largest prime factor of 600851475143.
I wrote some code and tried to optimize it based on some other Stack ...
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1answer
57 views
Project Euler #58: Primes along the diagonals of a square spiral
I am working on Project Euler Problem 58:
Starting with 1 and spiralling anticlockwise in the following way, a
square spiral with side length 7 is formed.
...
6
votes
1answer
171 views
Down to Zero II
Problem : https://www.hackerrank.com/challenges/down-to-zero-ii
You are given queries. Each query consists of a single number N. You can perform 2 operations on N in each move.
If N=a*b (a!=1,b!=...
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2answers
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Project Euler Problem #3 in Java - Largest Prime Factor
I have solved the problem and it gives me the right output when the BigInteger has the smaller value, however it kept running for more than 20 minutes with the ...
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4answers
160 views
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1answer
59 views
Efficient Prime Sieve - Haskell
I'm new to Haskell, and am trying to learn the basics with a simple function that will calculate the list of primes up to a given value (using the Sieve of Eratosthenes). Here is my code so far, which ...
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3answers
99 views
Lucas sequence implementation
Could you suggest any improvements in this Lucas sequence's implementation:
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3answers
386 views
Finding out the prime factors of a number
This finds the prime factors of a number given in a variable. Is it efficient or in need of improvement?
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2answers
65 views
Testing Goldbach's Conjecture hypothesis
A book1 that I'm reading states Goldbach's conjecture as follows:
Every even integer > 2 could be represented as a sum of two prime numbers.
Every integer > 17 could be represented as a sum of ...
2
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1answer
40 views
Postponed Prime Sequence in Kotlin
Following my previous unbounded prime generator and a followup by Martin R, I've tested the waters in Kotlin by making an unbounded sieve.
To quote Martin R's wonderful explanation of the base ...
3
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1answer
95 views
SICP exercise 1.28 - miller-rabin primality test part II
This is a follow-up to SICP exercise 1.28 - miller-rabin primality test.
Exercise 1.28:
One variant of the Fermat test that cannot be fooled is
called the Miller-Rabin test (Miller 1976; ...
2
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1answer
80 views
Generating numbers that are a product of consecutive primes
I have implemented a correct but horribly coded solution to Project Euler Problem 293.
An even positive integer N will be called admissible, if it is a power
of 2 or its distinct prime factors ...
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1answer
56 views
Project Euler 12 (triangle numbers), solved using functools.reduce() and looping
I have solved problem 12 on Project Euler website, which reads:
The sequence of triangle numbers is generated by adding the natural
numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 +...
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2answers
99 views
Simple Input Text Analysis
I've started learning java. I've written a small program I've done in C before. It's simple input analysis. If there is
number, program checks if number is prime. Then write number: (value of input ...
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2answers
72 views
Multithreaded brute force prime generator
A number is a prime when it is divisible by 1 and the number itself. To check if a given number is a prime we can divide the number by primes which are less than the square root of that number. If ...
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1answer
46 views
Stateful prime_numbers class for searching and storing primes
Title says the biggest part. The class is designed to be used to search for very big prime numbers, hence the element type is templated. The performance, neither in space nor time, is considered. ...
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3answers
75 views
Check if given number can be expressed as sum of 2 prime numbers
Similar problem: Sum Of Prime
I've done the given problem in roughly \$\mathcal{O}(n\sqrt{n})\$.
How can I improve this algorithm?
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2answers
187 views
Find prime numbers from 1 to 100
Create a program to find all the prime numbers between 1 and 100.
One way to do this is to write a function that will check if a number is prime (i.e., see if the number can be divided by a prime ...
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1answer
42 views
Simple Factor Class
I have a class which lazily factors numbers. It provides the user with these methods:
getFactors returns a ...
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3answers
72 views
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2answers
75 views
Another Python prime-listing algorithm
I wrote a small program in Python that finds primes (how original) up to some limit. I tried to produce very clean code, so I'd be vary grateful if you could point out any improvement I could do to ...
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2answers
149 views
Postponed Prime Sieve in Swift
Motivated by this question, I looked out for other "infinite prime generators", i.e. functions which produce the list of prime numbers in increasing order and do not have an a-priori upper limit (such ...
3
votes
1answer
110 views
Find the 10001st prime number (in C++)
I wrote this solution for project Euler #7, to find the 10001th prime number using sieve of eratosthenes. It's really slow though. Any suggestions to improve performance (without using more complex ...
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1answer
115 views
Unbounded Sieve of Eratosthenes in Swift
I've spent a while teaching myself Swift, and decided to take on the challenge of writing an unbounded Sieve of Eratosthenes to challenge myself. This is actually the first time I've written an ...
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3answers
145 views
Finds all the prime numbers up to n using a strange pattern
Here's an odd pattern I found for sieving out composite numbers to find primes. I wrote it myself, originally thinking I made an indexing error, but it turned out to work after removing squares.
<...
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2answers
109 views
Sieve of Eratosthenes and twin prime finder
I made this program to find primes and twin pairs. I'd like feedback on anything from formatting to content to technique. In short: how would this be different if it was written by an experienced ...
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1answer
60 views
The Miller-Rabin Primality Test in Clojure
I am new to clojure and I wanted to test out my skills by taking an existing implementation written in Python and writing it in Clojure.
Concerns
My main concerns are where I use ...
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1answer
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Looking for primes with all-different digits
I recently answered a question on Mathematics Stack Exchange, where I used a small Python program to check the following :
For all 6-digit numbers, with all digits being different, choosing the ...
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0answers
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Computation of primality
I believe I have achieved computation of primality! That is, the computation of prime numbers. The code I am about to post will give you every prime there is, in order, starting with 2. Can we call ...
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3answers
276 views
PrimeFactorize method for int
I have written this PrimeFactorize utility method in C# (using LINQPad) which works fine, but feels like it is a bit slow, I was wondering what might be improved. ...
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1answer
110 views
Approaching a C++ library with templates
I previously posted a thread asking for a general review of one of my first projects related to programming (C++ Prime Number Library) and received very good help and new perspectives. After this, I ...
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1answer
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TLE on SPOJ for Prime Generator (PRIME1)
The objective is to find all primes between two given numbers. It is specified that the two numbers are \$\le\$ 1 billion and the difference between the two numbers is ~100,000. We are to repeat the ...
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4answers
603 views
Project Euler 3: Largest prime factor
How can I improve my code, make it more efficient, and are there any tips you have?
Project Euler 3:
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the ...
0
votes
0answers
39 views
Palindromic prime search using the Sieve of Atkins
I am working on a project that deals with prime numbers and am currently looking for a way to make the function max_palprime() work faster and possibly simpler.
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3answers
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