手写LRU

数据结构为 DLNode + HashMap 

import java.util.HashMap;

/**

* Created by Administrator on 2019/7/14 0014.

*/

class LRUCache {

private int count;

private int capacity;

private HashMapcache =new HashMap<>();

private DLNodepre;

private DLNodepost;

public LRUCache(int capacity) {

count =0;

this.capacity = capacity;

pre =new DLNode();

pre.setPre(null);

post =new DLNode();

post.setPost(null);

pre.setPost(post);

post.setPre(pre);

}

public int get(int key) {

DLNode node =cache.get(key);

if(node ==null){

return -1;

}

DLNode tempPre  = node.getPre();

DLNode tempPost = node.getPost();

tempPre.setPost(tempPost);

tempPost.setPre(tempPre);

node.setPost(pre.getPost());

node.setPre(pre);

pre.getPost().setPre(node);

pre.setPost(node);

return node.value;

}

public void put(int key,int value) {

DLNode node =cache.get(key);

if(node ==null){//不存在

            node =new DLNode(key,value);

cache.put(key,node);

count++;

if(count>capacity){//移除尾部

                DLNode reNode =post.getPre();

reNode.getPre().setPost(node);

post.setPost(node);

node.setPre(reNode.getPre());

node.setPost(post);

cache.remove(reNode.key);

count--;

}else{

post.getPre().setPost(node);

node.setPre(post.getPre());

node.setPost(post);

}

}else{

DLNode tempPre = node.getPre();

DLNode tempPost = node.getPost();

node.value= value;

tempPre.setPost(tempPost);

tempPost.setPre(tempPre);

node.setPost(pre.getPost());

node.setPre(pre);

pre.getPost().setPre(node);

pre.setPost(node);

}

}

}

/**

* Created by Administrator on 2019/7/14 0014.

*/

public class DLNode {

public int key;

public int value;

private DLNodepre;

private DLNodepost;

public DLNode(){

}

public DLNode(int key,int value){

this.key = key;

this.value = value;

}

public DLNode getPre(){

return this.pre;

}

public void setPre(DLNode pre){

this.pre = pre;

}

public DLNode getPost(){

return this.post;

}

public void setPost(DLNode post){

this.post = post;

}

}