Package g0101_0200.s0146_lru_cache

Class LRUCache

  • All Implemented Interfaces:
    
public final class LRUCache

    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

    • <code>0 <= key <= 10<sup>4</sup></code>

    • <code>0 <= value <= 10<sup>5</sup></code>

    • At most <code>2 * 10<sup>5</sup></code> calls will be made to get and put.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      public final class LRUCache.Node

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      LRUCache(Integer capacity)

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer get(Integer key)
      final Unit put(Integer key, Integer value)
      final Unit add(LRUCache.Node node)

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait