Coding Solutions

Let's find if a number is prime. A prime number (or a prime) is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. The first few prime numbers are {2, 3, 5, 7, 11, ….}.
Here we have some solutions:

PHP: using bcmod and a for loop

function isPrimeNumber(int $num)
{
    for ($i = 2; $i <= $num - 1; $i++) {
        if (bcmod($num, $i) == 0) {
            return false;
        }
    }

    return ($num == $i);
}

var_dump( isPrimeNumber(4) ); // false
var_dump( isPrimeNumber(11) ); // true

Python: following the Wikipedia algorithm

def isPrime(n) : 
  
    # Corner cases 
    if (n <= 1) : 
        return False
    if (n <= 3) : 
        return True
  
    # This is checked so that we can skip  
    # middle five numbers in below loop 
    if (n % 2 == 0 or n % 3 == 0) : 
        return False
  
    i = 5
    while(i * i <= n) : 
        if (n % i == 0 or n % (i + 2) == 0) : 
            return False
        i = i + 6
  
    return True

# Driver Program  
if (isPrime(11)) : 
    print(" true") 
else : 
    print(" false") 
      
if(isPrime(15)) : 
    print(" true") 
else :  
    print(" false")

Java: using square

import java.util.Scanner;
import java.util.Scanner;

public class PrimeExample {

   public static void main(String[] args) {
       Scanner s = new Scanner(System.in);
       System.out.print("Enter a number : ");
       int n = s.nextInt();
       if (isPrime(n)) {
           System.out.println(n + " is a prime number");  
       } else {
           System.out.println(n + " is not a prime number");  
       }
   }
  
   public static boolean isPrime(int n) {  
       if (n <= 1) {
           return false;
       }
       for (int i = 2; i < Math.sqrt(n); i++) {  
           if (n % i == 0) {
               return false;
           }
       }
       return true;
   }
}