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LRU Cache Design - Linked Lists | Data Structures | Repovive

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Data Structures19 sections · 729 units49h total

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LRU Cache Design

Combining structures

The insight: use a hash map that stores pointers to list nodes.

class LRUCache:
    capacity: integer
    map: HashMap<key, DListNode>
    head: DListNode  # dummy
    tail: DListNode  # dummy

For get(key):

$1.$ Look up node in hash map— $O(1)$

$2.$ Move node to front of list (most recently used)— $O(1)$

$3.$ Return node's value

For put(key, value):

$1.$ If key exists, update value and move to front

$2.$ If new key and at capacity, remove node at back (LRU), delete from map

$3.$ Create new node, add to front, add to map

Every operation is $O(1)$ .