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lru-cache.py
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lru-cache.py
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# https://leetcode.com/problems/lru-cache/
class Node:
def __init__(self, key: int, value: int):
self.key = key
self.value = value
self.next = None
self.prev = None
class LinkedList:
def __init__(self):
self.head = None
self.tail = None
self.size = 0
def addHead(self, node: Node):
if self.head is None:
self.head = self.tail = node
else:
node.next = self.head
self.head.prev = node
self.head = self.head.prev
self.size += 1
def removeTail(self):
node = self.tail
self.tail = self.tail.prev
if self.tail is None:
self.head = None
else:
self.tail.next = None
node.prev = None
self.size -= 1
def removeHead(self):
node = self.head
self.head = self.head.next
if self.head is None:
self.tail = None
else:
self.head.prev = None
node.next = None
self.size -= 1
def remove(self, node: Node):
if node is self.head:
self.removeHead()
elif node is self.tail:
self.removeTail()
else:
node.prev.next = node.next
node.next.prev = node.prev
node.next = node.prev = None
self.size -= 1
class LRUCache:
def __init__(self, capacity: int):
self.capacity = capacity
self.nodes = {}
self.cachelist = LinkedList()
def get(self, key: int) -> int:
if key not in self.nodes:
return -1
node = self.nodes[key]
if node is not self.cachelist.head:
self.cachelist.remove(node)
self.cachelist.addHead(node)
return self.nodes[key].value
def put(self, key: int, value: int) -> None:
if key not in self.nodes:
if self.cachelist.size == self.capacity:
lrukey = self.cachelist.tail.key
del self.nodes[lrukey]
self.cachelist.removeTail()
node = Node(key, value)
self.nodes[key] = node
self.cachelist.addHead(node)
else:
node = self.nodes[key]
if node is not self.cachelist.head:
self.cachelist.remove(node)
self.cachelist.addHead(node)
self.nodes[key].value = value