LRU Cache
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.
思路:
双向链表
我的代码:
public class LRUCache { public LRUCache(int capacity) { this.capacity = capacity; this.head = new Node(-1, -1); this.tail = new Node(-1, -1); head.next = tail; tail.pre = head; } public int get(int key) { if(!hm.containsKey(key)) return -1; Node node = hm.get(key); //remove current node.pre.next = node.next; node.next.pre = node.pre; moveTotail(node); return node.val; } public void set(int key, int value) { if(get(key) != -1) { hm.get(key).val = value; return; } if(hm.size() == capacity) { hm.remove(head.next.key); head.next = head.next.next; head.next.pre = head; } Node node = new Node(key,value); hm.put(key,node); moveTotail(node); } public void moveTotail(Node node){ node.pre = tail.pre; node.next = tail; tail.pre.next = node; tail.pre = node; } private Node head; private Node tail; private int capacity; private HashMap<Integer,Node> hm = new HashMap<Integer,Node>(); private class Node{ Node pre; Node next; int key; int val; public Node(int key, int val) { this.key = key; this.val = val; } } }
学习之处:
- 在做这道题的时候,一下子就想到双向链表了,由于自己觉得简单,就边看答案边做的,差评!!!
- 这道题有点眼高手低,以后不能这样!其实好长时间才AC的
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