Hi, I'm Jitu.

class Node:
    def __init__(self, key: int, val: int):
        self.key, self.val = key, val
        self.prev = self.next = None

class LRUCache:
    """O(1) Get and Put via Hash Map + Doubly Linked List"""
    def __init__(self, capacity: int):
        self.cap = capacity
        self.cache = {} # key -> Node
        self.head, self.tail = Node(0, 0), Node(0, 0)
        self.head.next, self.tail.prev = self.tail, self.head

    def _remove(self, node: Node):
        prev, nxt = node.prev, node.next
        prev.next, nxt.prev = nxt, prev

    def _insert(self, node: Node):
        nxt = self.head.next
        self.head.next = node
        node.prev, node.next = self.head, nxt
        nxt.prev = node

    def get(self, key: int) -> int:
        if key in self.cache:
            node = self.cache[key]
            self._remove(node)
            self._insert(node)
            return node.val
        return -1

    def put(self, key: int, val: int) -> None:
        if key in self.cache:
            self._remove(self.cache[key])
        node = Node(key, val)
        self._insert(node)
        self.cache[key] = node
        if len(self.cache) > self.cap:
            lru = self.tail.prev
            self._remove(lru)
            del self.cache[lru.key]