From 1cfd6d045226a896506515f847061fdc304b6eb7 Mon Sep 17 00:00:00 2001 From: TzeMingHo Date: Wed, 17 Jun 2026 19:44:55 +0100 Subject: [PATCH 1/2] completed implement_lru_cache --- Sprint-2/implement_lru_cache/linked_list.py | 69 +++++++++++++++++++++ Sprint-2/implement_lru_cache/lru_cache.py | 29 +++++++++ 2 files changed, 98 insertions(+) create mode 100644 Sprint-2/implement_lru_cache/linked_list.py diff --git a/Sprint-2/implement_lru_cache/linked_list.py b/Sprint-2/implement_lru_cache/linked_list.py new file mode 100644 index 0000000..28b5c10 --- /dev/null +++ b/Sprint-2/implement_lru_cache/linked_list.py @@ -0,0 +1,69 @@ +class Node: + def __init__(self, key, value): + self.key = key + self.value = value + self.previous = None + self.next = None + +class LinkedList: + def __init__(self): + self.head = None + self.tail = None + + def push_head(self, new_node): + new_node.previous = None + new_node.next = None + + if self.head == None: + self.head = new_node + self.tail = new_node + else: + new_node.next = self.head + self.head.previous = new_node + self.head = new_node + + return new_node + + def pop_tail(self): + + if self.tail == None: + return None + + return self.remove(self.tail) + + def remove(self, node): + if self.head == None and self.tail == None: + return + + new_previous = node.previous + new_next = node.next + + if self.head == node and self.tail == node: + self.head = None + self.tail = None + elif self.head == node : + new_next.previous = None + self.head = new_next + elif self.tail == node: + new_previous.next = None + self.tail = new_previous + elif new_next and new_previous: + new_previous.next = new_next + new_next.previous = new_previous + + node.previous = None + node.next = None + return node + + def push_tail(self, new_node): + new_node.previous = None + new_node.next = None + + if self.tail == None: + self.tail = new_node + self.head = new_node + else: + self.tail.next = new_node + new_node.previous = self.tail + self.tail = new_node + return new_node \ No newline at end of file diff --git a/Sprint-2/implement_lru_cache/lru_cache.py b/Sprint-2/implement_lru_cache/lru_cache.py index e69de29..88b7ac4 100644 --- a/Sprint-2/implement_lru_cache/lru_cache.py +++ b/Sprint-2/implement_lru_cache/lru_cache.py @@ -0,0 +1,29 @@ +from linked_list import LinkedList, Node + +class LruCache: + def __init__(self, limit): + if limit <= 0: + raise ValueError("limit must be positive") + self.limit = limit + self.dict = {} + self.linked_list = LinkedList() + + def get(self, key): + if key not in self.dict: + return None + else: + most_recent_node = self.linked_list.remove(self.dict[key]) + self.linked_list.push_head(most_recent_node) + return most_recent_node.value + + def set(self, key, value): + if key in self.dict: + self.dict[key].value = value + self.get(key) + else: + if len(self.dict) == self.limit: + removed_node = self.linked_list.pop_tail() + del self.dict[removed_node.key] + self.dict[key] = Node(key, value) + self.linked_list.push_head(self.dict[key]) + From dfaa47182a78ce3b11151c2584d4026b7fbae85e Mon Sep 17 00:00:00 2001 From: TzeMingHo Date: Sat, 20 Jun 2026 14:16:19 +0100 Subject: [PATCH 2/2] refactored a method to move a node to front, and added slots --- Sprint-2/implement_lru_cache/linked_list.py | 8 ++++++-- Sprint-2/implement_lru_cache/lru_cache.py | 13 +++++++++---- 2 files changed, 15 insertions(+), 6 deletions(-) diff --git a/Sprint-2/implement_lru_cache/linked_list.py b/Sprint-2/implement_lru_cache/linked_list.py index 28b5c10..1f34510 100644 --- a/Sprint-2/implement_lru_cache/linked_list.py +++ b/Sprint-2/implement_lru_cache/linked_list.py @@ -1,4 +1,6 @@ class Node: + __slots__ = ("key", "value", "previous", "next") + def __init__(self, key, value): self.key = key self.value = value @@ -6,6 +8,8 @@ def __init__(self, key, value): self.next = None class LinkedList: + __slots__ = ("head", "tail") + def __init__(self): self.head = None self.tail = None @@ -33,7 +37,7 @@ def pop_tail(self): def remove(self, node): if self.head == None and self.tail == None: - return + return None new_previous = node.previous new_next = node.next @@ -66,4 +70,4 @@ def push_tail(self, new_node): self.tail.next = new_node new_node.previous = self.tail self.tail = new_node - return new_node \ No newline at end of file + return new_node diff --git a/Sprint-2/implement_lru_cache/lru_cache.py b/Sprint-2/implement_lru_cache/lru_cache.py index 88b7ac4..82f6104 100644 --- a/Sprint-2/implement_lru_cache/lru_cache.py +++ b/Sprint-2/implement_lru_cache/lru_cache.py @@ -1,6 +1,8 @@ from linked_list import LinkedList, Node class LruCache: + __slots__ = ("limit", "dict", "linked_list") + def __init__(self, limit): if limit <= 0: raise ValueError("limit must be positive") @@ -12,18 +14,21 @@ def get(self, key): if key not in self.dict: return None else: - most_recent_node = self.linked_list.remove(self.dict[key]) - self.linked_list.push_head(most_recent_node) - return most_recent_node.value + return self.move_to_front(self.dict[key]).value def set(self, key, value): if key in self.dict: self.dict[key].value = value - self.get(key) + self.move_to_front(self.dict[key]) else: if len(self.dict) == self.limit: removed_node = self.linked_list.pop_tail() del self.dict[removed_node.key] self.dict[key] = Node(key, value) self.linked_list.push_head(self.dict[key]) + + def move_to_front(self, node): + most_recent_node = self.linked_list.remove(node) + self.linked_list.push_head(most_recent_node) + return most_recent_node