Refactor remove_duplicates function to improve time complexity and update documentation

Author: mervereis

Sprint-1/Python/remove_duplicates/remove_duplicates.py

@@ -1,25 +1,24 @@
-from typing import List, Sequence, TypeVar
+def remove_duplicates(values):
 
-ItemType = TypeVar("ItemType")
-
-
-def remove_duplicates(values: Sequence[ItemType]) -> List[ItemType]:
-    """
-    Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
-
-    Time complexity:
-    Space complexity:
-    Optimal time complexity:
-    """
     unique_items = []
+    seen = set()
 
     for value in values:
-        is_duplicate = False
-        for existing in unique_items:
-            if value == existing:
-                is_duplicate = True
-                break
-        if not is_duplicate:
+        if value not in seen:
             unique_items.append(value)
+            seen.add(value)
 
     return unique_items
+
+
+print(remove_duplicates([1, 2, 2, 3, 1, 4]))
+# [1, 2, 3, 4]
+
+"""
+Remove duplicate values from a sequence,
+preserving the order of the first occurrence.
+
+Time complexity: O(n²)
+Space complexity: O(n)
+Optimal time complexity: O(n)
+"""