前往小程序,Get更优阅读体验!
立即前往
首页
学习
活动
专区
工具
TVP
发布
社区首页 >专栏 >LeetCode460.LFU缓存

LeetCode460.LFU缓存

作者头像
mathor
发布2018-08-16 16:39:47
3560
发布2018-08-16 16:39:47
举报
文章被收录于专栏:mathor
题目链接:LeetCode460
代码语言:javascript
复制
public class LFUCache {
    
    private TreeMap<Integer,LinkedHashSet<Integer>> numTreeMap; // k:num,v:timeLinkedHashSet
    private HashMap<Integer,int[]> valueHashMap; // k:key,v:int[value,num]
    private int capacity;
    public LFUCache(int capacity) {
        this.capacity = capacity;
        numTreeMap = new TreeMap<>();
        valueHashMap = new HashMap<>();
    }

    public int get(int key) {
        if(!valueHashMap.containsKey(key))
            return -1;
        int v = valueHashMap.get(key)[0];
        plusToTreeMap(key);
        return v;
    }

    public void put(int key, int value) {
        if(capacity == 0)
            return;
        if(valueHashMap.containsKey(key)) {
            plusToTreeMap(key);
            valueHashMap.put(key,new int[]{value,valueHashMap.get(key)[1]});
        } else 
            if(valueHashMap.size() == capacity)
                removeFromCache();
            valueHashMap.put(key,new int[]{value,1});
            addToTreeMap(key);
    }

    //新的key被put后,将valueHashMap中的num设成1,并在numTreeMap.get(1)中放入该key
    private void addToTreeMap(int key) {
        LinkedHashSet<Integer> timeLinkedList;
        if(!numTreeMap.containsKey(1)) {
            timeLinkedList = new LinkedHashSet<>();
            numTreeMap.put(1,timeLinkedList);
        } else 
            timeLinkedList = numTreeMap.get(1);
        timeLinkedList.add(key);
    }

    //已有key被get或put后,要修改两个地方,一个是valueHashMap中的num++,一个是提升该key在numTreeMap中的位置。
    private void plusToTreeMap(int key) {
        LinkedHashSet<Integer> timeLinkedList;
        int num = valueHashMap.get(key)[1]++;
        timeLinkedList = numTreeMap.get(num);
        timeLinkedList.remove(key);
        if(timeLinkedList.size() == 0)
            numTreeMap.remove(num);
        if(!numTreeMap.containsKey(num+1)) {
            timeLinkedList = new LinkedHashSet<>();
            numTreeMap.put(num+1,timeLinkedList);
        } else 
            timeLinkedList = numTreeMap.get(num+1);
        timeLinkedList.add(key);
    }
    
    private void removeFromCache() {
        LinkedHashSet<Integer> timeLinkedList = numTreeMap.firstEntry().getValue();
        int k = timeLinkedList.iterator().next();
        timeLinkedList.remove(k);
        valueHashMap.remove(k);
        if(timeLinkedList.size() == 0)
            numTreeMap.remove(numTreeMap.firstEntry().getKey());
    }
}
/**
 * Your LFUCache object will be instantiated and called as such:
 * LFUCache obj = new LFUCache(capacity);
 * int param_1 = obj.get(key);
 * obj.put(key,value);
 */
本文参与 腾讯云自媒体同步曝光计划,分享自作者个人站点/博客。
原始发表:2018-08-15,如有侵权请联系 cloudcommunity@tencent.com 删除

本文分享自 作者个人站点/博客 前往查看

如有侵权,请联系 cloudcommunity@tencent.com 删除。

本文参与 腾讯云自媒体同步曝光计划  ,欢迎热爱写作的你一起参与!

评论
登录后参与评论
0 条评论
热度
最新
推荐阅读
目录
  • 题目链接:LeetCode460
领券
问题归档专栏文章快讯文章归档关键词归档开发者手册归档开发者手册 Section 归档