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1 from typing import Optional
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2
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3
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4 class Node:
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5 def __init__(self, key, value):
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6 self.key = key
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7 self.value = value
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8 self.next: Optional[Node] = None
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9 self.prev: Optional[Node] = None
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10
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11 class LRUCache:
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12
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13 def __init__(self, capacity: int):
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14 self.capacity = capacity
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15 self.map = {}
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16 self.head = Node(-1, -1)
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17 self.tail = Node(-1, -1)
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18 self.head.next, self.tail.prev = self.tail, self.head
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19
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20 def get(self, key: int) -> int:
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21 if not key in self.map:
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22 return -1
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23 node = self.map[key]
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24 self._deleteAndAdd(node)
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25 return node.value
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26
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27 def put(self, key: int, value: int) -> None:
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28 newNode = Node(key, value)
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29 if key in self.map:
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30 self._delete(self.map[key])
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31 else:
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32 if len(self.map.keys())+1 > self.capacity:
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33 del self.map[self.head.next.key]
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34 self._delete(self.head.next)
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35 self._add(newNode)
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36 self.map[key] = newNode
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37
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38 def _deleteAndAdd(self, node):
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39 self._delete(node)
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40 self._add(node)
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41
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42 def _delete(self, node):
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43 node.prev.next, node.next.prev = node.next, node.prev
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44
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45 def _add(self, node):
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46 node.prev, node.next, self.tail.prev.next, self.tail.prev = self.tail.prev, self.tail, node, node
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