exercism 81 prime_factors

Author: kumar91gopi

Diff for: README.md

@@ -306,6 +306,7 @@ solution of many challenges of [Leetcode](https://leetcode.com/), [Exercism](htt
 78. [Binary Search Tree](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/binary_search_tree.rb)
 79. [Rotational Cipher](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/rotational_cipher.rb)
 80. [Largest Series Product](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/largest_series_product.rb)
+81. [Prime Factors](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/prime_factors.rb)
 
 <a name="leetcode"/>
 

Diff for: exercism/prime_factors.rb

@@ -0,0 +1,28 @@
+# Problem: https://exercism.org/tracks/ruby/exercises/prime-factors
+
+# Solution
+class PrimeFactors
+  def self.of(n)
+    return [] if n<2
+    prime_factors = []
+    factor = 2
+    while n>1
+      while n%factor ==0
+        prime_factors<<factor
+        n/=factor
+      end
+      factor+=1
+    end
+    prime_factors
+  end
+end
+
+# Solution (Recursive)
+class PrimeFactors
+    def self.of(n)
+      return [] if n < 2
+      factor = (2..n).find { |i| n % i == 0 }
+      [factor] + of(n / factor)
+    end
+end
+