Sheffield | 25-SDC-Nov | Sheida Shabankari | Sprint 2 | Implement LRU cache in python

[sheida-shab]

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PR Summary :
Implement LRU Cache with O(1) get/set operations

Description:
This PR adds a fully functional LRU (Least Recently Used) cache in Python. The implementation includes:

Node class: Represents a key-value pair with pointers to previous and next nodes.

Doubly linked list: Maintains the order of nodes for LRU eviction in O(1) time.

push_head: Moves or adds a node to the head (most recently used).

pop_tail: Removes and returns the tail node (least recently used).

remove: Removes a specific node from the list.

LruCache class: Provides the cache interface.

get(key): Retrieves a value by key and marks the node as most recently used.

set(key, value): Adds or updates a key-value pair; evicts the least recently used node if the cache exceeds its limit.

Handles invalid cache limits by raising ValueError.

Each operation (get and set) has O(1) worst-case time complexity.

Testing:

Unit tests cover cache limit enforcement, eviction order, and get/set functionality.