diff --git a/data_structures/arrays/remove_elements.rb b/data_structures/arrays/remove_elements.rb
index 6176ba1..b8c36e3 100644
--- a/data_structures/arrays/remove_elements.rb
+++ b/data_structures/arrays/remove_elements.rb
@@ -54,9 +54,17 @@ puts remove_elements([0,1,2,2,3,0,4,2], 2)
 # => 5
 
 #
-# Approach 3: Two-pointer
+# Approach 3: Two-pointers
 #
 
+# Complexity analysis
+#
+# Time complexity: O(n). Both i and n traverse at most n steps.
+# In this approach, the number of assignment operations is equal to the
+# number of elements to remove.
+#
+# Space complexity: O(1)
+
 def remove_element(nums, val)
   pointer1 = 0
   pointer2 = nums.length