Implement an LRU cache

LRU Cache Implementation

Design and implement a data structure for a Least Recently Used (LRU) cache. It should support the following operations: get and put.

• LRUCache(int capacity): Initialize the LRU cache with a positive size capacity.
• int get(int key): Return the value of the key if the key exists, otherwise return -1.
• void put(int key, int value): Update the value of the key if the key exists. Otherwise, add the key-value pair to the cache. If the number of keys exceeds the capacity from this operation, evict the least recently used key.

The get and put operations must each run in O(1) average time complexity.

Function Signature

class LRUCache:
    def __init__(self, capacity: int):
        pass

    def get(self, key: int) -> int:
        pass

    def put(self, key: int, value: int) -> None:
        pass

Examples

Example 1:

Input: ["LRUCache", "put", "put", "get", "put", "get", "put", "get", "get", "get"]
       [[2], [1, 1], [2, 2], [1], [3, 3], [2], [4, 4], [1], [3], [4]]
Output: [null, null, null, 1, null, -1, null, -1, 3, 4]

Explanation:

1. Initialize cache with capacity 2.
2. Put(1, 1), Put(2, 2) -> Cache is {1:1, 2:2}
3. Get(1) -> Returns 1, cache order becomes {2:2, 1:1}
4. Put(3, 3) -> Cache full, evict key 2. Cache is {1:1, 3:3}
5. Get(2) -> Returns -1 (not found)
6. Put(4, 4) -> Cache full, evict key 1. Cache is {3:3, 4:4}

Constraints

• 1 <= capacity <= 3000
• 0 <= key <= 10^4
• 0 <= value <= 10^5
• Total operations will not exceed 2 * 10^5.