exercism 63- perfect numbers

Author: kumar91gopi

README.md

@@ -280,6 +280,7 @@ solution of many challenges of [Leetcode](https://leetcode.com/), [Exercism](htt
 60. [Parallel Letter Frequency](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/parallel_letter_frequency.rb)
 61. [Bob](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/bob.rb)
 62. [Nth Prime](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/nth_prime.rb)
+63. [Perfect Numbers](https://github.com/kumar91gopi/Algorithms-and-Data-Structures-in-Ruby/blob/master/exercism/perfect_numbers.rb)
 
 <a name="leetcode"/>
 

exercism/perfect_numbers.rb

@@ -0,0 +1,24 @@
+# Problem: https://exercism.org/tracks/ruby/exercises/perfect-numbers
+
+# Solution
+class PerfectNumber
+    def self.classify(num)
+      raise RuntimeError if num<=0
+      factor_sum = 1
+      for i in 2..(Math.sqrt(num).ceil)
+        if num%i==0
+          factor_sum+=i
+          factor_sum+=(num/i) unless i*i == num
+        end
+      end
+      comparison = factor_sum <=> num
+      case comparison
+      when 0
+        "perfect"
+      when 1
+        "abundant"
+      when -1
+        "deficient"
+      end
+    end
+end