From 08e1383a429a30b98aaaad2822e526db7fd0a470 Mon Sep 17 00:00:00 2001
From: Gabriel <deng93003@gmail.com>
Date: Mon, 12 Jan 2026 15:32:55 +0000
Subject: [PATCH] This is the implementation of the lru cache

---
 Sprint-2/implement_lru_cache/lru_cache.py | 57 +++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/Sprint-2/implement_lru_cache/lru_cache.py b/Sprint-2/implement_lru_cache/lru_cache.py
index e69de29..47c100e 100644
--- a/Sprint-2/implement_lru_cache/lru_cache.py
+++ b/Sprint-2/implement_lru_cache/lru_cache.py
@@ -0,0 +1,57 @@
+class Node:
+    def __init__(self, key, value):
+        self.key = key
+        self.value = value
+        self.prev = None
+        self.next = None
+
+
+class LruCache:
+    def __init__(self, limit):
+        if limit <= 0:
+            raise ValueError("Capacity must be greater than 0")
+        self.capacity = limit
+        self.cache = {}
+
+        self.head = Node(None, None)
+        self.tail = Node(None, None)
+
+        self.head.next = self.tail
+        self.tail.prev = self.head
+
+    def _remove(self, node):
+        prev_node = node.prev
+        next_node = node.next
+        prev_node.next = next_node
+        next_node.prev = prev_node
+
+    def _add_to_front(self, node):
+        node.prev = self.head
+        node.next = self.head.next
+        self.head.next.prev = node
+        self.head.next = node
+
+    def get(self, key):
+        if key not in self.cache:
+            return None
+
+        node = self.cache[key]
+        self._remove(node)
+        self._add_to_front(node)
+        return node.value
+
+    def set(self, key, value):
+        if key in self.cache:
+            node = self.cache[key]
+            node.value = value
+            self._remove(node)
+            self._add_to_front(node)
+        else:
+            new_node = Node(key, value)
+            self.cache[key] = new_node
+            self._add_to_front(new_node)
+
+            if len(self.cache) > self.capacity:
+                lru = self.tail.prev
+                self._remove(lru)
+                del self.cache[lru.key]