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LeetCode-146 LRU 缓存

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LeetCode-146 LRU 缓存 #

Solution 1 #

使用双向链表和哈希表来维护数据.

代码如下:

class Node:
    __slots__ = 'prev', 'next', 'key', 'value'
    
    def __init__(self, key=0, value=0):
        self.key = key
        self.value = value

class LRUCache:

    def __init__(self, capacity: int):
        self.capacity = capacity
        self.dummy = Node()
        self.dummy.prev = self.dummy
        self.dummy.next = self.dummy
        self.key_to_node = dict()

    def get_node(self, key: int) -> Optional[Node]:
        if key not in self.key_to_node:
            return None
        node = self.key_to_node[key]
        self.remove(node)
        self.push_front(node)
        return node

    def get(self, key: int) -> int:
        node = self.get_node(key)
        return node.value if node else -1

    def put(self, key: int, value: int) -> None:
        node = self.get_node(key)
        if node:
            node.value = value
            return
        self.key_to_node[key] = node = Node(key, value)
        self.push_front(node)
        if len(self.key_to_node) > self.capacity:
            back_node = self.dummy.prev
            del self.key_to_node[back_node.key]
            self.remove(back_node)

    def remove(self, x: Node) -> None:
        x.prev.next = x.next
        x.next.prev = x.prev

    def push_front(self, x: Node) -> None:
        x.prev = self.dummy
        x.next = self.dummy.next
        x.prev.next = x
        x.next.prev = x