mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-30 16:31:08 +00:00
5f4da5d616
* updating DIRECTORY.md
* isort --profile black .
* Black after
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
65 lines
1.9 KiB
Python
65 lines
1.9 KiB
Python
import sys
|
|
from abc import abstractmethod
|
|
from collections import deque
|
|
|
|
|
|
class LRUCache:
|
|
""" Page Replacement Algorithm, Least Recently Used (LRU) Caching."""
|
|
|
|
dq_store = object() # Cache store of keys
|
|
key_reference_map = object() # References of the keys in cache
|
|
_MAX_CAPACITY: int = 10 # Maximum capacity of cache
|
|
|
|
@abstractmethod
|
|
def __init__(self, n: int):
|
|
""" Creates an empty store and map for the keys.
|
|
The LRUCache is set the size n.
|
|
"""
|
|
self.dq_store = deque()
|
|
self.key_reference_map = set()
|
|
if not n:
|
|
LRUCache._MAX_CAPACITY = sys.maxsize
|
|
elif n < 0:
|
|
raise ValueError("n should be an integer greater than 0.")
|
|
else:
|
|
LRUCache._MAX_CAPACITY = n
|
|
|
|
def refer(self, x):
|
|
"""
|
|
Looks for a page in the cache store and adds reference to the set.
|
|
Remove the least recently used key if the store is full.
|
|
Update store to reflect recent access.
|
|
"""
|
|
if x not in self.key_reference_map:
|
|
if len(self.dq_store) == LRUCache._MAX_CAPACITY:
|
|
last_element = self.dq_store.pop()
|
|
self.key_reference_map.remove(last_element)
|
|
else:
|
|
index_remove = 0
|
|
for idx, key in enumerate(self.dq_store):
|
|
if key == x:
|
|
index_remove = idx
|
|
break
|
|
self.dq_store.remove(index_remove)
|
|
|
|
self.dq_store.appendleft(x)
|
|
self.key_reference_map.add(x)
|
|
|
|
def display(self):
|
|
"""
|
|
Prints all the elements in the store.
|
|
"""
|
|
for k in self.dq_store:
|
|
print(k)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
lru_cache = LRUCache(4)
|
|
lru_cache.refer(1)
|
|
lru_cache.refer(2)
|
|
lru_cache.refer(3)
|
|
lru_cache.refer(1)
|
|
lru_cache.refer(4)
|
|
lru_cache.refer(5)
|
|
lru_cache.display()
|