From e4d90e2d5b92fdcff558f1848843dfbe20d81035 Mon Sep 17 00:00:00 2001
From: amirsoroush <114881632+amirsoroush@users.noreply.github.com>
Date: Sat, 1 Apr 2023 09:26:43 +0300
Subject: [PATCH] change space complexity of linked list's __len__ from O(n) to
 O(1) (#8183)

---
 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 67a63cd55..9092fb29e 100644
--- a/data_structures/linked_list/circular_linked_list.py
+++ b/data_structures/linked_list/circular_linked_list.py
@@ -24,7 +24,7 @@ class CircularLinkedList:
                 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 6c81493ff..41d07d63e 100644
--- a/data_structures/linked_list/doubly_linked_list.py
+++ b/data_structures/linked_list/doubly_linked_list.py
@@ -51,7 +51,7 @@ class DoublyLinkedList:
         >>> 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 61e2412aa..ca0d3bb48 100644
--- a/data_structures/linked_list/merge_two_lists.py
+++ b/data_structures/linked_list/merge_two_lists.py
@@ -44,7 +44,7 @@ class SortedLinkedList:
         >>> 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 bdeb5922a..a8f9e8ebb 100644
--- a/data_structures/linked_list/singly_linked_list.py
+++ b/data_structures/linked_list/singly_linked_list.py
@@ -72,7 +72,7 @@ class LinkedList:
         >>> len(linked_list)
         0
         """
-        return len(tuple(iter(self)))
+        return sum(1 for _ in self)
 
     def __repr__(self) -> str:
         """