Package g0101_0200.s0146_lru_cache

Class LRUCache

java.lang.Object
g0101_0200.s0146_lru_cache.LRUCache
public class LRUCache extends java.lang.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 Summary

    Constructors
    Constructor
    Description
    LRUCache(int cap)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    get(int key)
     
    void
    put(int key, int value)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • LRUCache

      public LRUCache(int cap)

  • Method Details

    • get

      public int get(int key)

    • put

      public void put(int key, int value)