NW | 26-SDC-Mar | Zabihollah Namazi | Sprint 2 | implement_lru_cache

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,68 @@
+class CacheNode:
+    def __init__(self, key, value):
+        self.key = key 
+        self.value = value 
+        self.previous = None
+        self.next = None        
+
+class LruCache:
+    def __init__(self, limit: int):
+        if limit <= 0:
+            raise ValueError("Cache limit must be greater than 0")
+
+        self.limit = limit
+        self.lookup = {}
+        self.head = None 
+        self.tail = None   
+
+    def _remove_node(self, node: CacheNode):
+        if node == self.head:
+            self.head = node.next
+        if node == self.tail:
+            self.tail = node.previous
+
+        if node.previous is not None:
+            node.previous.next = node.next
+        if node.next is not None:
+            node.next.previous = node.previous
+
+        node.next = None
+        node.previous = None
+
+    def _move_to_head(self, node: CacheNode):
+        node.next = self.head
+        node.previous = None
+
+        if self.head is None:
+            self.head = node
+            self.tail = node
+        else:
+            self.head.previous = node
+            self.head = node
+
+    def get(self, key):
+        if key not in self.lookup:
+            return None
+
+        node = self.lookup[key]
+        self._remove_node(node)
+        self._move_to_head(node)
+        return node.value
+
+    def set(self, key, value) -> None:
+        if key in self.lookup:
+            node = self.lookup[key]
+            node.value = value
+            self._remove_node(node)
+            self._move_to_head(node)
+        else:
+            new_node = CacheNode(key, value)
+
+            if len(self.lookup) >= self.limit:
+                oldest_node = self.tail
+                if oldest_node is not None:
+                    del self.lookup[oldest_node.key]  
+                    self._remove_node(oldest_node)    
+
+            self._move_to_head(new_node)
+            self.lookup[key] = new_node