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Added LRU Cache #2138
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Original file line number | Diff line number | Diff line change |
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class Double_Linked_List_Node(): | ||
''' | ||
Double Linked List Node built specifically for LRU Cache | ||
''' | ||
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def __init__(self, key, val): | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Type hits please |
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self.key = key | ||
self.val = val | ||
self.next = None | ||
self.prev = None | ||
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class Double_Linked_List(): | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Same as above |
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''' | ||
Double Linked List built specifically for LRU Cache | ||
''' | ||
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def __init__(self): | ||
self.head = Double_Linked_List_Node(None, None) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. How about a sensible default in the method declaration? |
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self.rear = Double_Linked_List_Node(None, None) | ||
self.head.next, self.rear.prev = self.rear, self.head | ||
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def add(self, node: Double_Linked_List_Node) -> None: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Needs doctests |
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''' | ||
Adds the given node to the end of the list (before rear) | ||
''' | ||
temp = self.rear.prev | ||
temp.next, node.prev = node, temp | ||
self.rear.prev, node.next = node, self.rear | ||
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def remove(self, node: Double_Linked_List_Node) -> Double_Linked_List_Node: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Needs doctests |
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''' | ||
Removes and returns the given node from the list | ||
''' | ||
temp_last, temp_next = node.prev, node.next | ||
node.prev, node.next = None, None | ||
temp_last.next, temp_next.prev = temp_next, temp_last | ||
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return node | ||
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class Lru_Cache: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Naming convention as suggested above |
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''' | ||
LRU Cache to store a given capacity of data | ||
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>>> cache = Lru_Cache(2) | ||
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>>> cache.set(1, 1) | ||
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>>> cache.set(2, 2) | ||
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>>> cache.get(1) | ||
1 | ||
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>>> cache.set(3, 3) | ||
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>>> cache.get(2) | ||
Traceback (most recent call last): | ||
... | ||
ValueError: Key '2' not found in cache | ||
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>>> cache.set(4, 4) | ||
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>>> cache.get(1) | ||
Traceback (most recent call last): | ||
... | ||
ValueError: Key '1' not found in cache | ||
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>>> cache.get(3) | ||
3 | ||
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>>> cache.get(4) | ||
4 | ||
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>>> cache.has_key(1) | ||
False | ||
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>>> cache.has_key(4) | ||
True | ||
''' | ||
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def __init__(self, capacity): | ||
self.list = Double_Linked_List() | ||
self.capacity = capacity | ||
self.num_keys = 0 | ||
self.cache = {} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Why have both a cache and a decorator_function_to_instance_map? Could we have one instead of two? There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. We need both as the cache maps the keys to the Double Linked List Node |
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
Thanks a lot :) 👍 |
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def get(self, key: int) -> int: | ||
''' | ||
Returns the value for the input key and updates the Double Linked List. Raises | ||
Value Error if key is not present in cache | ||
''' | ||
if key in self.cache: | ||
self.list.add(self.list.remove(self.cache[key])) | ||
return self.cache[key].val | ||
raise ValueError(f"Key '{key}' not found in cache") | ||
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def set(self, key: int, value: int) -> None: | ||
''' | ||
Sets the value for the input key and updates the Double Linked List | ||
''' | ||
if key not in self.cache: | ||
if self.num_keys >= self.capacity: | ||
key_to_delete = self.list.head.next.key | ||
self.list.remove(self.cache[key_to_delete]) | ||
del self.cache[key_to_delete] | ||
self.num_keys -= 1 | ||
self.cache[key] = Double_Linked_List_Node(key, value) | ||
self.list.add(self.cache[key]) | ||
self.num_keys += 1 | ||
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else: | ||
node = self.list.remove(self.cache[key]) | ||
node.val = value | ||
self.list.add(node) | ||
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def has_key(self, key: int) -> bool: | ||
''' | ||
Checks if the input key is present in cache | ||
''' | ||
return key in self.cache | ||
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if __name__ == "__main__": | ||
import doctest | ||
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doctest.testmod() |
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Do not use
snake_cases
for class naming. Also, no()
needed as you are not subclassing from any class.You might wanna try