设计LRU缓存结构

[1,-1]

[1,-1,-1,3,4]

import java.util.*;

public class Solution {
/**
* lru design
* @param operators int整型二维数组 the ops
* @param k int整型 the k
* @return int整型一维数组
*/
static class Node{
int key,value;
Node prev,next;
public Node(int key,int value){
this.key = key;
this.value = value;
}
}
private Map<Integer,Node> map = new HashMap<>();
private Node head = new Node(-1,-1);
private Node tail = new Node(-1,-1);
private int k;
public int[] LRU (int[][] operators, int k) {
// write code here
this.k = k;
head.next = tail;
tail.prev = head;
int len = (int) Arrays.stream(operators).filter(x->x[0]==2).count();
int[] ans = new int[len];
int cnt = 0;
for(int i=0;i<operators.length;i++){
if(operators[i][0] == 1){
set(operators[i][1],operators[i][2]);
}else{
ans[cnt++] = get(operators[i][1]);
}
}
return ans;
}

private void set(int key,int value){
if(get(key) > -1){
map.get(key).value = value;
}else{
if(map.size() == k){
int rk = tail.prev.key;
tail.prev.prev.next = tail;
tail.prev = tail.prev.prev;
map.remove(rk);
}
Node node = new Node(key,value);
map.put(key,node);
removeToHead(node);
}
return;
}

private int get(int key){
if(map.containsKey(key)){
Node node = map.get(key);
node.next.prev = node.prev;
node.prev.next = node.next;
//removetohead
removeToHead(node);
return node.value;
}
return -1;
}
public void removeToHead(Node node){
node.next = head.next;
head.next.prev = node;
head.next = node;
node.prev = head;
}


}