112 lines
3.1 KiB
Java
112 lines
3.1 KiB
Java
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/*
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This is a Java Program to Implement Solovay Strassen Primality Test Algorithm. Solovay Strassen Primality Test is an algorithm which is used to determine if a given number is prime or not.
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*/
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/**
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** Java Program to Implement SolovayStrassen Primality Test Algorithm
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**/
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import java.util.Scanner;
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import java.util.Random;
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/** Class SolovayStrassen **/
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public class SolovayStrassen
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{
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/** Function to calculate jacobi (a/b) **/
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public long Jacobi(long a, long b)
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{
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if (b <= 0 || b % 2 == 0)
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return 0;
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long j = 1L;
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if (a < 0)
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{
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a = -a;
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if (b % 4 == 3)
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j = -j;
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}
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while (a != 0)
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{
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while (a % 2 == 0)
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{
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a /= 2;
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if (b % 8 == 3 || b % 8 == 5)
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j = -j;
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}
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long temp = a;
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a = b;
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b = temp;
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if (a % 4 == 3 && b % 4 == 3)
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j = -j;
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a %= b;
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}
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if (b == 1)
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return j;
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return 0;
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}
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/** Function to check if prime or not **/
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public boolean isPrime(long n, int iteration)
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{
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/** base case **/
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if (n == 0 || n == 1)
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return false;
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/** base case - 2 is prime **/
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if (n == 2)
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return true;
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/** an even number other than 2 is composite **/
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if (n % 2 == 0)
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return false;
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Random rand = new Random();
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for (int i = 0; i < iteration; i++)
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{
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long r = Math.abs(rand.nextLong());
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long a = r % (n - 1) + 1;
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long jacobian = (n + Jacobi(a, n)) % n;
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long mod = modPow(a, (n - 1)/2, n);
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if(jacobian == 0 || mod != jacobian)
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return false;
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}
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return true;
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}
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/** Function to calculate (a ^ b) % c **/
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public long modPow(long a, long b, long c)
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{
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long res = 1;
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for (int i = 0; i < b; i++)
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{
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res *= a;
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res %= c;
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}
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return res % c;
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}
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/** Main function **/
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public static void main (String[] args)
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{
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Scanner scan = new Scanner(System.in);
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System.out.println("SolovayStrassen Primality Algorithm Test\n");
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/** Make an object of SolovayStrassen class **/
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SolovayStrassen ss = new SolovayStrassen();
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/** Accept number **/
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System.out.println("Enter number\n");
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long num = scan.nextLong();
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/** Accept number of iterations **/
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System.out.println("\nEnter number of iterations");
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int k = scan.nextInt();
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/** check if prime **/
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boolean prime = ss.isPrime(num, k);
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if (prime)
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System.out.println("\n"+ num +" is prime");
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else
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System.out.println("\n"+ num +" is composite");
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}
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}
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/*
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Enter number
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9997777
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Enter number of iterations
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1
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9997777 is prime
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