#241: lru cache

09-problems/lc_146_lru_cache.py

@@ -0,0 +1,76 @@
+class Doubly_Linked_Node:
+    def __init__(self, key: int):
+        self.prev = None
+        self.next = None
+        self.key = key
+
+class Doubly_Linked_List:
+    def __init__(self, head: Doubly_Linked_Node, tail: Doubly_Linked_Node):
+        self.head = head
+        self.tail = tail
+
+    def add(self, node: Doubly_Linked_Node):
+        if self.tail == None:
+            self.head = node
+            self.tail = node
+
+        else:
+            self.tail.next = node
+            node.prev = self.tail
+            self.tail = node
+
+    def remove(self, node: Doubly_Linked_Node):
+        if node == self.head == self.tail:
+            self.head = None
+            self.tail = None
+
+        elif node == self.head:
+            self.head = self.head.next
+            self.head.prev = None
+
+        elif node == self.tail:
+            self.tail = self.tail.prev
+            self.tail.next = None
+
+        elif node.prev and node.next:
+            node.prev.next = node.next
+            node.next.prev = node.prev
+
+class LRUCache:
+    def __init__(self, capacity: int):
+        self.__capacity = capacity
+
+        self.__key_node_dict = {}
+        self.__key_value_dict = {}
+        self.__linked_list = Doubly_Linked_List(None, None)
+
+    def get(self, key: int) -> int:
+        val = self.__key_value_dict.get(key, -1)
+        if val == -1:
+            return -1
+
+        key_node = self.__key_node_dict[key]
+
+        self.__linked_list.remove(key_node)
+        self.__linked_list.add(key_node)
+
+        return val
+
+    def put(self, key: int, value: int) -> None:
+
+        self.__key_value_dict[key] = value
+
+        key_node = self.__key_node_dict.get(key, None)
+        if (key_node):
+            self.__linked_list.remove(key_node)
+        else:
+            key_node = Doubly_Linked_Node(key)
+            self.__key_node_dict[key] = key_node
+        self.__linked_list.add(key_node)
+
+        if len(self.__key_value_dict) > self.__capacity:
+            self.__key_node_dict.pop(self.__linked_list.head.key)
+            self.__key_value_dict.pop(self.__linked_list.head.key)
+            self.__linked_list.remove(self.__linked_list.head)
+
+