Ports - Angela

lib/factorial.rb

@@ -1,6 +1,19 @@
 # Computes factorial of the input number and returns it
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n) where n is number
+# Space complexity: O(1)
 def factorial(number)
-  raise NotImplementedError
+  raise ArgumentError, "Number is invalid!" if number == nil
+
+  if number >= 1
+    return number * factorial(number - 1)
+  else
+    return 1
+  end
+
+  # factorial = 1
+  # while number > 0
+  #   factorial *= number
+  #   number -= 1
+  # end
+  # return factorial
 end

specs/factorial_spec.rb

@@ -1,5 +1,8 @@
+gem "minitest", ">= 5.0.0"
+
 require 'minitest/autorun'
 require 'minitest/reporters'
+require "minitest/pride"
 require_relative '../lib/factorial'
 
 describe "factorial" do