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.
Follow up:
Could you do both operations in O(1) time complexity?
class LRUCache {
int capacity; Map map = new HashMap();//key是Integer，value是Node Node head = null; Node end = null; public LRUCache(int capacity) { this.capacity = capacity; } public int get(int key) { if(map.containsKey(key)) { Node temp = map.get(key); remove(temp); setHead(temp); return temp.value; } return -1; } public void put(int key, int value) { if(map.containsKey(key)) { Node old = map.get(key); old.value = value; remove(old); setHead(old); } else { Node created = new Node(key,value); if(map.size()>=capacity) { map.remove(end.key); remove(end); setHead(created); } else setHead(created); map.put(key,created); } } public void remove(Node n) { if(n.pre!=null) n.pre.next = n.next; else head = n.next; if(n.next!=null) n.next.pre = n.pre; else end = n.pre; } public void setHead(Node n) { n.next = head; n.pre = null; if(head!=null) head.pre=n; head = n; if(end == null) end = head; } } class Node { int key; int value; Node pre; Node next; Node(int key, int value){ this.key = key; this.value = value; } } 标签：146,Node,pre,map,int,value,key,LRUCache From： https://www.cnblogs.com/MarkLeeBYR/p/16908991.html