London | 26-SDC-Mar | Ebrahim Beiati-Asl | Sprint 2 | implement_lru_cache

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,64 @@
+class DLLNode:
+    def __init__(self, key, value):
+        self.key = key
+        self.value = value
+        self.prev = None
+        self.next = None
+
+
+class DoublyLinkedList:
+    def __init__(self):
+        self.head = DLLNode(None, None)
+        self.tail = DLLNode(None, None)
+        self.head.next = self.tail
+        self.tail.prev = self.head
+
+    def add_to_front(self, node):
+        node.next = self.head.next
+        node.prev = self.head
+        self.head.next.prev = node
+        self.head.next = node
+
+    def remove(self, node):
+        node.prev.next = node.next
+        node.next.prev = node.prev
+
+    def move_to_front(self, node):
+        self.remove(node)
+        self.add_to_front(node)
+
+    def remove_last(self):
+        if self.tail.prev is self.head:
+            return None
+        last = self.tail.prev
+        self.remove(last)
+        return last
+
+
+class LruCache:
+    def __init__(self, capacity: int):
+        self.capacity = capacity
+        self.cache = {}
+        self.list = DoublyLinkedList()
+
+    def get(self, key):
+        if key not in self.cache:
+            return -1
+        node = self.cache[key]
+        self.list.move_to_front(node)
+        return node.value
+
+    def put(self, key, value):
+        if key in self.cache:
+            node = self.cache[key]
+            node.value = value
+            self.list.move_to_front(node)
+            return
+
+        new_node = DLLNode(key, value)
+        self.cache[key] = new_node
+        self.list.add_to_front(new_node)
+
+        if len(self.cache) > self.capacity:
+            last = self.list.remove_last()
+            del self.cache[last.key]