题解 | #设计LRU缓存结构#

沙雕题解：

import java.util.*;


public class Solution  {
    int capacity;
    HashMap<Integer,Node> hashmap;
    Node head;
    Node tail;
    public  class Node{
        Node left;
        Integer key;
        Integer value;
        Node right;

        public Node(Integer key, Integer value) {
            this.left = null;
            this.key = key;
            this.value = value;
            this.right = null;
        }

        public Node getLeft() {
            return left;
        }

        public void setLeft(Node left) {
            this.left = left;
        }

        public Node getRight() {
            return right;
        }

        public void setRight(Node right) {
            this.right = right;
        }

        public Integer getKey() {
            return key;
        }

        public void setKey(Integer key) {
            this.key = key;
        }

        public Integer getValue() {
            return value;
        }

        public void setValue(Integer value) {
            this.value = value;
        }
    }
     
    public Solution(int capacity){
        hashmap = new HashMap<>(capacity);
        this.capacity = capacity;
        
    }
    public int get(int key) {
         // write code here
        if (hashmap.containsKey(key)){
            int value = hashmap.get(key).getValue();
            if (hashmap.get(key) == tail && (head != tail)){
                tail = tail.getLeft();
                tail.setRight(null);
                hashmap.get(key).setLeft(null);
                hashmap.remove(key);
                set(key,value);
            } else if(hashmap.get(key) == head && (head != tail)){
                set(key,value);
            } else if (head != tail){
                Node node = hashmap.get(key);
                node.getLeft().setRight(node.getRight());
                node.getRight().setLeft(node.getLeft());
                node.setLeft(null);
                node.setRight(null);
                hashmap.remove(key);
                set(key,value);
            }
            return head.getValue();
        } else {
            return -1;
        }
    }

    public void set(int key, int value) {
         // write code here
        if (hashmap.containsKey(key)){
            if (hashmap.get(key) == tail && (head != tail)){
                tail = tail.getLeft();
                tail.setRight(null);
                hashmap.get(key).setLeft(null);
                hashmap.remove(key);
                set(key,value);
            } else if(hashmap.get(key) == head && (head != tail)){
                head = head.getRight();
                head.setLeft(null);
                hashmap.get(key).setLeft(null);
                hashmap.remove(key);
                set(key,value);
            } else if (head != tail){
                Node node = hashmap.get(key);
                node.getLeft().setRight(node.getRight());
                node.getRight().setLeft(node.getLeft());
                node.setLeft(null);
                node.setRight(null);
                hashmap.remove(key);
                set(key,value);
            } else{
                hashmap.get(key).setValue(value);
            }
        } else {
            if (hashmap.size() == capacity) {
                tail = tail.getLeft();
                hashmap.remove(tail.getRight().getKey());
            }

            Node node = new Node(key, value);
            if (head == null) {
                head = node;
                tail = node;
            } else {
                head.setLeft(node);
                node.setRight(head);
                head = node;
            }
            hashmap.put(key, node);
        }
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * Solution solution = new Solution(capacity);
 * int output = solution.get(key);
 * solution.set(key,value);
 */