Update data_structures/arrays/two_sum.rb

data_structures/arrays/two_sum.rb

@@ -76,7 +76,11 @@ print two_sum([3, 3], 6)
 #
 # Approach 3: Using a Hash
 #
-# Time Complexity: O(N), where N is the length of the array
+# Time complexity: O(n). We traverse the list containing n elements exactly twice.
+# Since the hash table reduces the lookup time to O(1), the time complexity is O(n).
+
+# Space complexity: O(n). The extra space required depends on the number of items
+# stored in the hash table, which stores exactly n elements.
 #
 def two_sum(nums, target)
   hash = {}