tail: added a third, memory efficient, solution.

tail/tail.py

@@ -1,13 +1,27 @@
 def tail_v1(sequence, count):
+    """My first take at this exercise."""
     if count <= 0:
         return list()
     return list(sequence[-count:])
 
 
 def tail_v2(sequence, count):
+    """This solution can handle any iterator."""
     if count <= 0:
         return []
     return list(list(sequence)[-count:])
 
 
-tail = tail_v2
+def tail_v3(iterable, n):
+    """Based on Trey's explanations, this solution is more memory efficient."""
+    result = []
+    if n > 0:
+        for element in iterable:
+            if n == 1:
+                result = [element]
+            else:
+                result = [*result[-n + 1 :], element]
+    return result
+
+
+tail = tail_v3