标签:leetcode cache java hashmap
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.
import java.util.HashMap; import java.util.LinkedList; class ListNode{ int key, value; ListNode next, prev; public ListNode() { this.key = this.value = 0; next = prev = null; } public ListNode(int key, int val) { this.key = key; this.value = val; next = prev = null; } } public class LRUCache { private ListNode head,tail; private HashMap<Integer, ListNode> hashmap; private int size, capacity; public static void main(String[] args) { // TODO Auto-generated method stub } public LRUCache(int capacity) { this.size = 0; this.capacity = capacity; head = new ListNode(); tail = new ListNode(); head.next = tail; tail.prev = head; hashmap = new HashMap<Integer, ListNode>(); } public int get(int key) { if (hashmap.containsKey(key)) { ListNode cur = hashmap.get(key); //detach the node in the list cur.prev.next = cur.next; cur.next.prev = cur.prev; //set the visting node be the firstNode. ListNode tmp = head.next; head.next = cur; cur.prev = head; cur.next = tmp; tmp.prev = cur; return cur.value; } else return -1; } public void set(int key, int value) { if (hashmap.containsKey(key)) { ListNode cur = hashmap.get(key); cur.value = value; //detach cur.prev.next = cur.next; cur.next.prev = cur.prev; //set the visting node be the firstNode. ListNode tmp = head.next; head.next = cur; cur.prev = head; cur.next = tmp; tmp.prev = cur; } else { if (size == capacity) { ListNode last = tail.prev; hashmap.remove(last.key); tail = last; last = null; size--; } ListNode cur = new ListNode(key, value); hashmap.put(key, cur); //set the new node be the firstNode. ListNode tmp = head.next; head.next = cur; cur.prev = head; cur.next = tmp; tmp.prev = cur; size++; } } }
【LeetCode】LRU Cache,布布扣,bubuko.com
标签:leetcode cache java hashmap
原文地址:http://blog.csdn.net/xiaozhuaixifu/article/details/26211487