Package g0101_0200.s0146_lru_cache

Class LRUCache

  • public class LRUCache
extends Object
    146 - LRU Cache.

    Medium

    Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.

    Implement the LRUCache class:

    • LRUCache(int capacity) Initialize the LRU cache with 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 functions get and put must each run in O(1) average time complexity.

    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:

     LRUCache lRUCache = new LRUCache(2);
 lRUCache.put(1, 1); // cache is {1=1}
 lRUCache.put(2, 2); // cache is {1=1, 2=2}
 lRUCache.get(1); // return 1
 lRUCache.put(3, 3); // LRU key was 2, evicts key 2, cache is {1=1, 3=3}
 lRUCache.get(2); // returns -1 (not found)
 lRUCache.put(4, 4); // LRU key was 1, evicts key 1, cache is {4=4, 3=3}
 lRUCache.get(1); // return -1 (not found)
 lRUCache.get(3); // return 3
 lRUCache.get(4); // return 4

    Constraints:

    • 1 <= capacity <= 3000
    • 0 <= key <= 104
    • 0 <= value <= 105
    • At most 2 * 105 calls will be made to get and put.

    • Constructor Detail

      • LRUCache

        public LRUCache​(int cap)

    • Method Detail

      • get

        public int get​(int key)

      • put

        public void put​(int key,
                int value)