LRU Cache
Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set.
get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.
set(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.
Solution
Hash + list.
import java.util.LinkedHashMap;
import java.util.Map;
public class LRUCache {
private Map<Integer, Integer> map;
private int capacity;
public LRUCache(int capacity) {
this.capacity = capacity;
map = new LinkedHashMap<Integer, Integer>(capacity + 1);
}
public int get(int key) {
Integer val = map.get(key);
if (val == null) return -1;
map.remove(key);
map.put(key, val);
return val;
}
public void set(int key, int value) {
map.remove(key);
map.put(key, value);
if (map.size() > capacity)
map.remove(map.entrySet().iterator().next().getKey());
}
}