94 lines
2.8 KiB
Java
94 lines
2.8 KiB
Java
/*
|
|
This is a Java Program to Implement Miller Rabin Primality Test Algorithm. Miller Rabin Primality Test is an algorithm which is used to determine if a given number is prime or not.
|
|
*/
|
|
|
|
/**
|
|
** Java Program to Implement Miller Rabin Primality Test Algorithm
|
|
**/
|
|
|
|
import java.util.Scanner;
|
|
import java.util.Random;
|
|
import java.math.BigInteger;
|
|
|
|
/** Class MillerRabin **/
|
|
public class MillerRabin
|
|
{
|
|
/** Function to check if prime or not **/
|
|
public boolean isPrime(long n, int iteration)
|
|
{
|
|
/** base case **/
|
|
if (n == 0 || n == 1)
|
|
return false;
|
|
/** base case - 2 is prime **/
|
|
if (n == 2)
|
|
return true;
|
|
/** an even number other than 2 is composite **/
|
|
if (n % 2 == 0)
|
|
return false;
|
|
long s = n - 1;
|
|
while (s % 2 == 0)
|
|
s /= 2;
|
|
Random rand = new Random();
|
|
for (int i = 0; i < iteration; i++)
|
|
{
|
|
long r = Math.abs(rand.nextLong());
|
|
long a = r % (n - 1) + 1, temp = s;
|
|
long mod = modPow(a, temp, n);
|
|
while (temp != n - 1 && mod != 1 && mod != n - 1)
|
|
{
|
|
mod = mulMod(mod, mod, n);
|
|
temp *= 2;
|
|
}
|
|
if (mod != n - 1 && temp % 2 == 0)
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
/** Function to calculate (a ^ b) % c **/
|
|
public long modPow(long a, long b, long c)
|
|
{
|
|
long res = 1;
|
|
for (int i = 0; i < b; i++)
|
|
{
|
|
res *= a;
|
|
res %= c;
|
|
}
|
|
return res % c;
|
|
}
|
|
/** Function to calculate (a * b) % c **/
|
|
public long mulMod(long a, long b, long mod)
|
|
{
|
|
return BigInteger.valueOf(a).multiply(BigInteger.valueOf(b)).mod(BigInteger.valueOf(mod)).longValue();
|
|
}
|
|
/** Main function **/
|
|
public static void main (String[] args)
|
|
{
|
|
Scanner scan = new Scanner(System.in);
|
|
System.out.println("Miller Rabin Primality Algorithm Test\n");
|
|
/** Make an object of MillerRabin class **/
|
|
MillerRabin mr = new MillerRabin();
|
|
/** Accept number **/
|
|
System.out.println("Enter number\n");
|
|
long num = scan.nextLong();
|
|
/** Accept number of iterations **/
|
|
System.out.println("\nEnter number of iterations");
|
|
int k = scan.nextInt();
|
|
/** check if prime **/
|
|
boolean prime = mr.isPrime(num, k);
|
|
if (prime)
|
|
System.out.println("\n"+ num +" is prime");
|
|
else
|
|
System.out.println("\n"+ num +" is composite");
|
|
}
|
|
}
|
|
|
|
/*
|
|
Enter number
|
|
|
|
5510389
|
|
|
|
Enter number of iterations
|
|
2
|
|
|
|
5510389 is prime
|