1 files changed, 65 insertions, 0 deletions
diff --git a/challenge-175/adam-russell/java/ch-2.java b/challenge-175/adam-russell/java/ch-2.java
new file mode 100644
index 0000000000..15232709ce
--- /dev/null
+++ b/challenge-175/adam-russell/java/ch-2.java
@@ -0,0 +1,65 @@
+import java.util.HashSet;
+import java.util.ArrayList;
+
+class PerfectTotient{
+
+    private static double EPSILON = 1e-7;  
+
+    private static ArrayList primeFactors(int n){
+        ArrayList factors = new ArrayList();    
+        while (n % 2 == 0){
+            factors.add(new Integer(2));
+            n = n / 2;
+        }
+        for(int i = 3; i <= Math.sqrt(n); i = i + 2){
+            while (n % i == 0){
+                factors.add(new Integer(i));
+                n = n / i;
+            }
+        }
+        if(n > 2)
+            factors.add(new Integer(n));
+        return factors;  
+    }
+
+    private static int totient(int n){
+        ArrayList factors = new ArrayList();
+        factors.addAll(new HashSet(primeFactors(n))); 
+        float totient = n;
+        for(int i = 0; i < factors.size(); i++){
+            totient *= (1 - (1.0 / ((Integer) factors.get(i)).intValue()));  
+        }  
+        return (int) totient; 
+    } 
+
+    public static int[] perfectTotients(int n){
+        int[] perfectTotients = new int[n];
+        int i = 0; 
+        int x = 1;
+        while(i < n){
+            x++;
+            ArrayList totients = new ArrayList(); 
+            int totient = totient(x);
+            totients.add(new Integer(totient)); 
+            while(Math.abs(totient - 1) > EPSILON){   
+                totient = totient(totient); 
+                totients.add(new Integer(totient)); 
+            }
+            int totientSum = 0;
+            for(int j = 0; j < totients.size(); j++)
+                totientSum += ((Integer)totients.get(j)).intValue();
+            if(totientSum == x){
+                perfectTotients[i] = x;
+                i++; 
+            }  
+        } 
+        return perfectTotients;  
+    } 
+
+    public static void main(String[] args){
+        int[] perfectTotients = perfectTotients(20);
+        for(int i = 0; i < perfectTotients.length - 1; i++)
+            System.out.print(perfectTotients[i] + ", ");    
+        System.out.println(perfectTotients[perfectTotients.length - 1]);  
+    }   
+}