add eular totient function

Author: joney000

Algorithms/EularTotient.java

@@ -0,0 +1,28 @@
+package Algorithms;
+
+class EularTotient {
+  /*
+  * compute the eular totient(https://en.wikipedia.org/wiki/Euler%27s_totient_function)
+  *   of the given numer, speeding up the computation when we have prime numbers 
+  * 
+  * time complexity: O(k log n) where k = no of prime factors
+  * this method is advantagious when we have large numbers whose prime factors
+  * are small numbers eg. eular totient of 16'402'500'000 = 2^5 * 3^8 * 5^7 can be computed
+  * in only 3 steps.
+  */
+  private long totient(long n , long primes[]){ 
+    long result = n;    
+    for(int i=0; primes[i] <= n; i++) 
+    {
+      if(n < primes[i])
+        break;
+      if(n % primes[i] == 0)
+        result -= result / primes[i]; 
+      while (n % primes[i] == 0)
+        n /= primes[i];
+    }
+    if(n > 1)
+      result -= result / n; 
+    return result; 
+  }
+}