what are prime numbers
Prime numbers: whole numbers greater than 1 that are only divisible by 1 and itself.
prime numbers
A number only divisible by 1 and itself
prime numbers
#include <iostream> #include <cmath> #include <iostream> #define el "\n" using namespace std; bool isprime(int n) { if (n <= 1) { return 0; } for(int i=2 ; i <= sqrt(n); i++) // [sqrt(n)] is faster in calculations than [n/2] { if(n%i == 0) { return 0; } } return 1; }; int main() { long long num; cin >> num; // ~~~ Enter a number (isprime(num))? cout << "The number (" << num <<") is a prime" << el : cout << "The number (" << num <<") isn't a prime" << el; return 0; }
Source: code.sololearn.com
what is prime number
Number which is only divisible by itself and 1(eg. 2,3...)
Prime Numbers
using System; public class Program { static void Main(string[] args) { var results = GenerateSieve(1000); var i=0; foreach (var item in results) { if(item) Console.Write(i + " "); i++; } } static bool[] GenerateSieve(int num) { // Creating an array indicating whether numbers are prime. bool[] isPrime = new bool[num + 1]; for (int i = 2; i <= num; i++) isPrime[i] = true; // Removing out multiples. for (int i = 2; i <= num; i++) { // Check if i is prime. if (isPrime[i]) { // Eliminate multiples of i. for (int j = i * 2; j <= num; j += i) isPrime[j] = false; } } return isPrime; } }
Source: ideone.com