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lrucache.py
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lrucache.py
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class Node:
def __init__(self, key, value):
self.key = key
self.value = value
self.prev = None
self.next = None
class lrucache():
def __init__(self, capacity):
self.hash_map = dict()
self.capacity = capacity
self.head = None
self.tail = None
def _addNode(self, new_node):
key = new_node.key
new_node.next = self.head
if self.head:
self.head.prev = new_node
self.head = new_node
if not self.tail:
self.tail = new_node
if not self.hash_map.get(key):
self.hash_map[key] = new_node
def _deleteNode(self, ex_node):
key = ex_node.key
# when a middle element is removed
if ex_node != self.head and ex_node != self.tail:
ex_node.prev.next = ex_node.next
ex_node.next.prev = ex_node.prev
# when head or tail is removed
else:
if self.head == ex_node:
self.head = self.head.next
ex_node.next = None
if self.tail == ex_node:
self.tail = self.tail.prev
ex_node.prev = None
self.hash_map.pop(key)
def get(self, key):
if self.hash_map.get(key):
req_node = self.hash_map[key]
if req_node != self.head:
self._deleteNode(req_node)
self._addNode(req_node)
return req_node.value
else:
return None
def put(self, key, value):
new_node = Node(key, value)
if len(self.hash_map) == self.capacity:
self._deleteNode(self.tail)
self._addNode(new_node)
LR = lrucache(5)
LR.put(1, 5)
LR.put(2, 6)
LR.get(1)
LR.put(3, 7)