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import datetime | |
import math | |
class Node: | |
def __init__(self, key, value, weight, lastAccess): | |
self.key = key | |
self.value = value | |
self.weight = weight | |
self.lastAccess = lastAccess | |
def __str__(self): | |
return '{}, {}, {}, lastAccess'.format(self.key, self.value, self.weight, self.lastAccess) | |
class Cache: | |
def __init__(self, capacity=4): | |
self.__itemKeys = [] | |
self.__hashMap = {} | |
self.__capacity = capacity | |
def __now(self): | |
return datetime.datetime.now() | |
def get(self, key): | |
try: | |
node = self.__hashMap[key] | |
node.lastAccess = self.__now() | |
return node.value | |
except KeyError: | |
return -1 | |
def put(self, key, value, weight): | |
newNode = Node(key, value, weight, self.__now()) | |
self.__hashMap[newNode.key] = newNode | |
self.__itemKeys.append(newNode.key) | |
if len(self.__itemKeys) > self.__capacity: | |
self.__handleExcess() | |
def __handleExcess(self): | |
self.__sortItems() | |
droppedKey = self.__itemKeys.pop() | |
del self.__hashMap[droppedKey] | |
def __sortItems(self): | |
self.__itemKeys.sort(key=self.__getScore, reverse=True) | |
def __getScore(self, key): | |
node = self.__hashMap[key] | |
return node.weight / math.log(self.__now - node.lastAccess) |
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