[mypy] Annotates other/least_recently_used over generic type

+ clean-up: rename key_reference to match type.

Author: spazm

other/least_recently_used.py

@@ -1,44 +1,47 @@
 import sys
 from collections import deque
+from typing import Generic, TypeVar
 
+T = TypeVar("T")
 
-class LRUCache:
+
+class LRUCache(Generic[T]):
     """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
+    dq_store: deque[T]  # Cache store of keys
+    key_reference: set[T]  # References of the keys in cache
     _MAX_CAPACITY: int = 10  # Maximum capacity of cache
 
-    def __init__(self, n: int):
+    def __init__(self, n: int) -> None:
         """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()
+        self.key_reference = 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):
+    def refer(self, x: T) -> None:
         """
         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 x not in self.key_reference:
             if len(self.dq_store) == LRUCache._MAX_CAPACITY:
                 last_element = self.dq_store.pop()
-                self.key_reference_map.remove(last_element)
+                self.key_reference.remove(last_element)
         else:
             self.dq_store.remove(x)
 
         self.dq_store.appendleft(x)
-        self.key_reference_map.add(x)
+        self.key_reference.add(x)
 
-    def display(self):
+    def display(self) -> None:
         """
         Prints all the elements in the store.
         """