1 files changed, 89 insertions, 0 deletions
diff --git a/challenge-168/adam-russell/java/ch-2.java b/challenge-168/adam-russell/java/ch-2.java
new file mode 100644
index 0000000000..ed2906c49f
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+++ b/challenge-168/adam-russell/java/ch-2.java
@@ -0,0 +1,89 @@
+import java.util.Random;
+import java.util.ArrayList;
+import java.math.BigInteger;
+import java.util.Collections;
+  
+/** Class MillerRabin **/
+/* Slightly modified version of code taken from 
+   https://www.sanfoundry.com/java-program-miller-rabin-primality-test-algorithm/ */
+class MillerRabin{
+    private static final int ITERATIONS = 7;
+    /** Function to check if prime or not **/
+    public static boolean isPrime(long n){
+        /** 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 < ITERATIONS; 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 static 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 static long mulMod(long a, long b, long mod){
+        return BigInteger.valueOf(a).multiply(BigInteger.valueOf(b)).mod(BigInteger.valueOf(mod)).longValue();
+    }
+}
+
+class HomePrime{
+    private static ArrayList primeFactors(long n){
+        ArrayList factors = new ArrayList();    
+        while (n % 2 == 0){
+            factors.add(new Long(2));
+            n = n / 2;
+        }
+        for(long i = 3; i <= Math.sqrt(n); i = i + 2){
+            while (n % i == 0){
+                factors.add(new Long(i));
+                n = n / i;
+            }
+        }
+        if(n > 2)
+            factors.add(new Long(n));
+        return factors;  
+    }
+    
+    public static long homePrime(long n){
+        ArrayList primeFactors = primeFactors(n);
+        String s = "";
+        for(int i = 0; i < primeFactors.size(); i++){
+           s += ((Long) primeFactors.get(i)).toString();
+        }
+        if(MillerRabin.isPrime(Long.valueOf(s).longValue())){
+            return Long.valueOf(s).longValue();
+        }
+        return homePrime(Long.valueOf(s).longValue());
+    }
+
+    public static void main(String[] args){        
+        System.out.println(HomePrime.homePrime(10));
+        System.out.println(HomePrime.homePrime(16));
+        System.out.println(HomePrime.homePrime(48));
+    }
+}
+\ No newline at end of file