Sockets - Karla

lib/factorial.rb

@@ -1,6 +1,14 @@
 # Computes factorial of the input number and returns it
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n-1) which is simplified to 0(n) where n is the value of the number
+# Space complexity: 0(1) because no additional space is being used in relation to the lenght of the input
 def factorial(number)
-  raise NotImplementedError
+  raise ArgumentError if number.nil?
+  return 1 if number == 0 || number == 1
+
+  i = number
+  until i == 1
+    i -= 1
+    number = number * i
+  end
+  return number
 end

specs/factorial_spec.rb

@@ -2,6 +2,8 @@
 require 'minitest/reporters'
 require_relative '../lib/factorial'
 
+Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
+
 describe "factorial" do
   describe "basic tests" do
     it "factorial(5) = 120" do