Solution
class Node:
def __init__(self, key: int = 0, val: int = 0):
self.key = key
self.val = val
self.prev = None
self.next = None
class LRUCache:
def __init__(self, capacity: int):
self.size = 0
self.capacity = capacity
self.cache = {}
self.head = Node()
self.tail = Node()
self.head.next = self.tail
self.tail.prev = self.head
def get(self, key: int) -> int:
if key not in self.cache:
return -1
node = self.cache[key]
self.remove_node(node)
self.add_to_head(node)
return node.val
def put(self, key: int, value: int) -> None:
if key in self.cache:
node = self.cache[key]
self.remove_node(node)
node.val = value
self.add_to_head(node)
else:
node = Node(key, value)
self.cache[key] = node
self.add_to_head(node)
self.size += 1
if self.size > self.capacity:
del_node = self.tail.prev
self.cache.pop(del_node.key)
self.remove_node(del_node)
self.size -= 1
def remove_node(self, node):
node.prev.next = node.next
node.next.prev = node.prev
def add_to_head(self, node):
node.next = self.head.next
node.prev = self.head
self.head.next = node
node.next.prev = node
if __name__ == "__main__":
cache = LRUCache(2)
cache.put(1,1)
cache.put(2,2)
print(cache.get(1))
cache.put(3,3)
print(cache.get(2))
cache.put(4,4)
print(cache.get(1))
print(cache.get(3))
print(cache.get(4))