题解 | #设计LRU缓存结构#

class Node {
    constructor(key, value) {
        this.key = key;
        this.value = value;
        this.prev = null;
        this.next = null;
    }
}
/**
 * @param {number} capacity
 */
var Solution = function (capacity) {
    // write code here
    this.capacity = capacity;
    this.cache = new Map();
    this.head = new Node();
    this.tail = new Node();
    this.head.next = this.tail;
    this.tail.prev = this.head;
};

/**
 * @param {number} key
 * @return {number}
 */
Solution.prototype.get = function (key) {
    // write code here
    if (this.cache.has(key)) {
        const node = this.cache.get(key);
        this.moveToHead(node);
        return node.value;
    } else {
        return -1;
    }
};

/**
 * @param {number} key
 * @param {number} value
 * @return {void}
 */
Solution.prototype.set = function (key, value) {
    // write code here
    if (this.cache.has(key)) {
        const node = this.cache.get(key);
        node.value = value;
    } else {
        if (this.cache.size === this.capacity) {
            const tailPrev = this.tail.prev;
            this.removeNode(tailPrev);
            this.cache.delete(tailPrev.key);
        }
        const newNode = new Node(key, value);
        this.cache.set(key, newNode);
        this.addToHead(newNode);
    }
};

Solution.prototype.addToHead = function (node) {
    node.prev = this.head;
    node.next = this.head.next;
    this.head.next.prev = node;
    this.head.next = node;
}

Solution.prototype.removeNode = function (node) {
    node.prev.next = node.next;
    node.next.prev = node.prev;
}

Solution.prototype.moveToHead = function (node) {
    this.removeNode(node);
    this.addToHead(node);
}

module.exports = {
    Solution: Solution,
};

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

双向链表+哈希表实现