leetcode-146-LRU缓存机制

题目描述：

方法一：有序字典 O(1)

from collections import OrderedDict
class LRUCache(OrderedDict):
def __init__(self, capacity: int):
self.capacity = capacity

def get(self, key: int) -> int:
if key not in self:
return - 1

self.move_to_end(key)
return self[key]

def put(self, key: int, value: int) -> None:
if key in self:
self.move_to_end(key)
self[key] = value
if len(self) > self.capacity:
self.popitem(last = False)

# Your LRUCache object will be instantiated and called as such:
# obj = LRUCache(capacity)
# param_1 = obj.get(key)
# obj.put(key,value)

方法二：哈希表加双向链表 O(1)

class DLinkedNode():
def __init__(self):
self.key = 0
self.value = 0
self.prev = None
self.next = None

class LRUCache:
def _add_node(self, node):
node.prev = self.head
node.next = self.head.next
self.head.next.prev = node
self.head.next = node

def _remove_node(self, node):
prev = node.prev
new = node.next
prev.next = new
new.prev = prev

def _move_to_head(self, node):
self._remove_node(node)
self._add_node(node)

def _pop_tail(self):
res = self.tail.prev
self._remove_node(res)
return res

def __init__(self, capacity: int):
self.cache = {}
self.size = 0
self.capacity = capacity
self.head, self.tail = DLinkedNode(), DLinkedNode()
self.head.next = self.tail
self.tail.prev = self.head

def get(self, key: int) -> int:
node = self.cache.get(key, None)
if not node: return -1
self._move_to_head(node)
return node.value

def put(self, key: int, value: int) -> None:
node = self.cache.get(key)
if not node:
newNode = DLinkedNode()
newNode.key = key
newNode.value = value
self.cache[key] = newNode
self._add_node(newNode)
self.size += 1
if self.size > self.capacity:
tail = self._pop_tail()
del self.cache[tail.key]
self.size -= 1
else:
node.value = value
self._move_to_head(node)

# Your LRUCache object will be instantiated and called as such:
# obj = LRUCache(capacity)
# param_1 = obj.get(key)
# obj.put(key,value)

转载于:https://www.cnblogs.com/oldby/p/11200936.html