From d4ca92cf66759d30481ced7723639b8984f3c2e2 Mon Sep 17 00:00:00 2001 From: Aida Eslami Date: Sun, 1 Mar 2026 18:38:04 +0000 Subject: [PATCH 1/3] implement linked list with O(1) operations --- Sprint-2/implement_linked_list/linked_list.py | 51 +++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py index e69de29b..a712132a 100644 --- a/Sprint-2/implement_linked_list/linked_list.py +++ b/Sprint-2/implement_linked_list/linked_list.py @@ -0,0 +1,51 @@ +class Node: + def __init__(self, value): + self.value = value + self.previous = None + self.next = None + + +class LinkedList: + def __init__(self): + self.head = None + self.tail = None + + def push_head(self, value): + new_node = Node(value) + + new_node.next = self.head + if self.head: + self.head.previous = new_node + + self.head = new_node + + if self.tail is None: + self.tail = new_node + + return new_node + + def pop_tail(self): + if self.tail is None: + return None + + removed = self.tail + + if self.tail.previous: + self.tail = self.tail.previous + self.tail.next = None + else: + self.head = None + self.tail = None + + return removed.value + + def remove(self, node): + if node.previous: + node.previous.next = node.next + else: + self.head = node.next + + if node.next: + node.next.previous = node.previous + else: + self.tail = node.previous \ No newline at end of file From eef38b3648ed001c17f9cf7667ce2fea0cca80a0 Mon Sep 17 00:00:00 2001 From: Aida Eslami Date: Sun, 1 Mar 2026 20:52:11 +0000 Subject: [PATCH 2/3] implement doubly linked list --- Sprint-2/implement_linked_list/linked_list.py | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py index a712132a..d4ee9711 100644 --- a/Sprint-2/implement_linked_list/linked_list.py +++ b/Sprint-2/implement_linked_list/linked_list.py @@ -16,12 +16,10 @@ def push_head(self, value): new_node.next = self.head if self.head: self.head.previous = new_node - - self.head = new_node - - if self.tail is None: + else: self.tail = new_node + self.head = new_node return new_node def pop_tail(self): @@ -44,6 +42,8 @@ def remove(self, node): node.previous.next = node.next else: self.head = node.next + if self.head: + self.head.previous = None if node.next: node.next.previous = node.previous From 16aa7a6873a7f8bcc682fe0912908d545486dc58 Mon Sep 17 00:00:00 2001 From: Aida Eslami Date: Mon, 22 Jun 2026 12:35:19 +0100 Subject: [PATCH 3/3] Refactor pop_tail to reuse remove method --- Sprint-2/implement_linked_list/linked_list.py | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/Sprint-2/implement_linked_list/linked_list.py b/Sprint-2/implement_linked_list/linked_list.py index d4ee9711..45fbc6d6 100644 --- a/Sprint-2/implement_linked_list/linked_list.py +++ b/Sprint-2/implement_linked_list/linked_list.py @@ -14,6 +14,7 @@ def push_head(self, value): new_node = Node(value) new_node.next = self.head + if self.head: self.head.previous = new_node else: @@ -27,13 +28,7 @@ def pop_tail(self): return None removed = self.tail - - if self.tail.previous: - self.tail = self.tail.previous - self.tail.next = None - else: - self.head = None - self.tail = None + self.remove(removed) return removed.value @@ -42,10 +37,12 @@ def remove(self, node): node.previous.next = node.next else: self.head = node.next - if self.head: - self.head.previous = None if node.next: node.next.previous = node.previous else: - self.tail = node.previous \ No newline at end of file + self.tail = node.previous + + + node.previous = None + node.next = None \ No newline at end of file