460. LFU Cache
有点做不动了。。。基本思想是。。。（这题要重看，先休息一会）
class ListNode(object):
def __init__(self, key, val):
self.prev = None
self.next = None
self.val = val
self.key = key
def connect(self, nextNode):
self.next = nextNode
nextNode.prev = self
class LFUCache(object):
def __init__(self, capacity):
"""
:type capacity: int
"""
self.cap = capacity
self.head = ListNode(None, None)
self.tail = ListNode(None, None)
self.head.connect(self.tail)
#use to record the first ListNode of this count number
self.cnt = {0: self.tail}
# key: key , value:[ListNode, visit count]
self.kv = {None:[self.tail, 0]}
def moveforward(self, key):
node, cnt = self.kv[key]
self.add('tmp', node.val, cnt + 1)
self.remove(key)
self.kv[key] = self.kv['tmp']
self.kv[key][0].key = key
del self.kv['tmp']
def get(self, key):
"""
:type key: int
:rtype: int
"""
if key not in self.kv:
return -1
self.moveforward(key)
return self.kv[key][0].val
def put(self, key, value):
"""
:type key: int
:type value: int
:rtype: void
"""
if self.cap == 0:
return
if key in self.kv:
self.kv[key][0].val = value
self.moveforward(key)
return
if len(self.kv) > self.cap:
self.remove(self.tail.prev.key)
self.add(key, value, 0)
def remove(self, key):
node, cnt = self.kv[key]
if self.cnt[cnt] != node:
node.prev.connect(node.next)
elif self.kv[node.next.key][1] == cnt:
node.prev.connect(node.next)
self.cnt[cnt] = self.cnt[cnt].next
else:
node.prev.connect(node.next)
del self.cnt[cnt]
del self.kv[key]
def add(self, key, value, cnt):
if cnt in self.cnt:
loc = self.cnt[cnt]
else:
loc = self.cnt[cnt - 1]
node = ListNode(key, value)
loc.prev.connect(node)
node.connect(loc)
self.cnt[cnt] = node
self.kv[key] = [node, cnt]
