1+ package com .leetcode .design ;
2+ 3+ import java .util .LinkedHashMap ;
4+ import java .util .Map ;
5+ 6+ import static org .junit .jupiter .api .Assertions .assertEquals ;
7+ 8+ /**
9+ * Level: Medium
10+ * Link: https://leetcode.com/problems/lru-cache/
11+ * Description:
12+ * Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following
13+ * operations: get and put.
14+ *
15+ * get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
16+ * put(key, value) - Set or insert the value if the key is not already present. When the cache reached its capacity, it
17+ * should invalidate the least recently used item before inserting a new item.
18+ *
19+ * The cache is initialized with a positive capacity.
20+ *
21+ * Follow up:
22+ * Could you do both operations in O(1) time complexity?
23+ *
24+ * Runtime: <a href="https://leetcode.com/submissions/detail/253383205/">54 ms</a>.
25+ *
26+ * @author rampatra
27+ * @since 2019年08月20日
28+ */
29+ public class LRUCache {
30+ 31+ private LinkedHashMap <Integer , Integer > cache ;
32+ 33+ public LRUCache (int capacity ) {
34+ this .cache = new LinkedHashMap <Integer , Integer >(capacity , 0.75f , true ) {
35+ @ Override
36+ protected boolean removeEldestEntry (Map .Entry eldest ) {
37+ return size () > capacity ;
38+ }
39+ };
40+ }
41+ 42+ public int get (int key ) {
43+ Integer val = cache .get (key );
44+ return val == null ? -1 : val ;
45+ }
46+ 47+ public void put (int key , int value ) {
48+ cache .put (key , value );
49+ }
50+ 51+ public static void main (String [] args ) {
52+ LRUCache cache = new LRUCache (2 );
53+ cache .put (1 ,1 );
54+ cache .put (2 ,2 );
55+ cache .put (1 ,1 );
56+ cache .put (3 ,3 );
57+ assertEquals (1 , cache .get (1 ));
58+ assertEquals (-1 , cache .get (2 ));
59+ assertEquals (3 , cache .get (3 ));
60+ }
61+ }
0 commit comments