Design and implement a data structure for Least
Recently Used (LRU) cache. It should support the following operations: get
and put.
get(key) - Get the value (will always be positive) of the key if the key exists
in the cache, otherwise return -1.
put(key, value) - Set or insert the value if the key is not already present.
When the cache reached its capacity, it should invalidate the least recently used item
before inserting a new item.
The cache is initialized with a positive capacity.
Follow up:
Could you do both operations in O(1) time complexity?
Example:
LRUCache cache = new LRUCache( 2 /* capacity */ ); cache.put(1, 1); cache.put(2, 2); cache.get(1); // returns 1 cache.put(3, 3); // evicts key 2 cache.get(2); // returns -1 (not found) cache.put(4, 4); // evicts key 1 cache.get(1); // returns -1 (not found) cache.get(3); // returns 3 cache.get(4); // returns 4