牛客网：NC93 设计LRU缓存结构

package com.company.test.设计LRU缓存结构;

import java.util.*;



public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution(2);
       
        solution.set(1,1);
        solution.set(2,2);
        solution.set(1,2);
        solution.set(3,3);
        System.out.println(solution.get(1));
    }

    Map cache;
    int size;
    int capacity;
    Node head;
    Node tail;

    public Solution(int capacity) {
        // write code here
        cache = new HashMap<>();
        size = 0;
        this.capacity = capacity;
        head = new Node();
        tail = new Node();
        head.next = tail;
        tail.pre = head;
    }

    private void remove(Node node){
        node.pre.next = node.next;
        node.next.pre = node.pre;
    }


    private void addHade(Node node){
        node.pre = head;
        node.next = head.next;
        head.next.pre = node;
        head.next = node;
    }

    private void moveToHead(Node node){
        remove(node);
        addHade(node);
    }

    private Node deletetail(){
        Node tail = this.tail.pre;
        remove(tail);
        return tail;
    }

    public int get(int key) {
        // write code here
        Node node = cache.get(key);
        if (node == null){
            return -1;
        }
        moveToHead(node);
        return node.value;
    }

    public void set(int key, int value) {
        // write code here
        Node node = cache.get(key);
        if (node == null){
            Node newNode = new Node(key, value);
            cache.put(key, newNode);
            addHade(newNode);
            size++;
            if (size > capacity){
                Node tail = deletetail();
                cache.remove(tail.key);
                size--;
            }
        } else{
            cache.get(key).value = value;
            moveToHead(node);
        }

    }


    class Node {
        int key;
        int value;
        Node pre;
        Node next;

        public Node (){};

        public Node (int key, int value){
            this.key = key;
            this.value = value;
        }
    }
}