From 810a4edc24c25db533672a139cc09cd814e0ee40 Mon Sep 17 00:00:00 2001
From: Amirsoroush <amirsoroush.dev@gmail.com>
Date: Wed, 15 Mar 2023 23:31:02 +0300
Subject: [PATCH] change space complexity of linked list's __len__ from O(n) to
 O(1)

---
 data_structures/linked_list/circular_linked_list.py | 2 +-
 data_structures/linked_list/doubly_linked_list.py   | 2 +-
 data_structures/linked_list/merge_two_lists.py      | 2 +-
 data_structures/linked_list/singly_linked_list.py   | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/data_structures/linked_list/circular_linked_list.py b/data_structures/linked_list/circular_linked_list.py
index 67a63cd55e19..9092fb29e3ff 100644
--- a/data_structures/linked_list/circular_linked_list.py
+++ b/data_structures/linked_list/circular_linked_list.py
@@ -24,7 +24,7 @@ def __iter__(self) -> Iterator[Any]:
                 break
 
     def __len__(self) -> int:
-        return len(tuple(iter(self)))
+        return sum(1 for _ in self)
 
     def __repr__(self):
         return "->".join(str(item) for item in iter(self))
diff --git a/data_structures/linked_list/doubly_linked_list.py b/data_structures/linked_list/doubly_linked_list.py
index 6c81493fff85..41d07d63e005 100644
--- a/data_structures/linked_list/doubly_linked_list.py
+++ b/data_structures/linked_list/doubly_linked_list.py
@@ -51,7 +51,7 @@ def __len__(self):
         >>> len(linked_list) == 5
         True
         """
-        return len(tuple(iter(self)))
+        return sum(1 for _ in self)
 
     def insert_at_head(self, data):
         self.insert_at_nth(0, data)
diff --git a/data_structures/linked_list/merge_two_lists.py b/data_structures/linked_list/merge_two_lists.py
index 61e2412aa7fd..ca0d3bb48540 100644
--- a/data_structures/linked_list/merge_two_lists.py
+++ b/data_structures/linked_list/merge_two_lists.py
@@ -44,7 +44,7 @@ def __len__(self) -> int:
         >>> len(SortedLinkedList(test_data_odd))
         8
         """
-        return len(tuple(iter(self)))
+        return sum(1 for _ in self)
 
     def __str__(self) -> str:
         """
diff --git a/data_structures/linked_list/singly_linked_list.py b/data_structures/linked_list/singly_linked_list.py
index bdeb5922ac67..a8f9e8ebb977 100644
--- a/data_structures/linked_list/singly_linked_list.py
+++ b/data_structures/linked_list/singly_linked_list.py
@@ -72,7 +72,7 @@ def __len__(self) -> int:
         >>> len(linked_list)
         0
         """
-        return len(tuple(iter(self)))
+        return sum(1 for _ in self)
 
     def __repr__(self) -> str:
         """