code for lru_cache

Author: sheetalkharab

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,75 @@
+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: int):
+        if limit <= 0:
+            raise ValueError("Cache limit must be greater than zero")
+
+        self.limit = limit
+        self.cache = {}
+        self.head = None    
+        self.tail = None
+        self.size = 0
+
+    
+    #to remove a node frpm linkedlist
+    def _remove_node(self, node: Node): 
+        if node.prev:
+            node.prev.next = node.next
+        else:
+            self.head = node.next
+
+        if node.next:
+            node.next.prev = node.prev
+        else:
+            self.tail = node.prev
+
+        node.prev = node.next = None
+
+
+    #Add a node to the head of the linked list
+    def _add_to_head(self, node: Node):
+        node.next = self.head
+        node.prev = None
+
+        if self.head:
+            self.head.prev = node
+        self.head = node
+
+        if not self.tail:
+            self.tail = node  
+
+
+    def get(self, key):
+        if key not in self.cache:
+            return None
+        node = self.cache[key]
+        # Move node to head (most recently used)
+        self._remove_node(node)
+        self._add_to_head(node)
+        return node.value
+
+
+    def set(self, key, value):
+        if key in self.cache:
+            node = self.cache[key]
+            node.value = value
+            self._remove_node(node)
+            self._add_to_head(node)
+        else:
+            node = Node(key, value)
+            self.cache[key] = node
+            self._add_to_head(node)
+            self.size += 1
+
+            if self.size > self.limit:
+                # Evict LRU (tail node)
+                lru = self.tail
+                self._remove_node(lru)
+                del self.cache[lru.key]
+                self.size -= 1