算法学习: leetcode146. LRU 缓存

这道题目主要通过双向链表，加映射表去实现。具体实现代码如下，思路可以参考这篇文章

/**
 * 实现节点
 * @param {*} k 
 * @param {*} v 
 */
let Node = function(k, v) {
    this.key = k;
    this.val = v;
    this.next = null;
    this.prev = null; 
}

/**
 * 实现双向链表
 */
let DoubleList = function() {
    this.head = new Node(0,0)
    this.tail = new Node(0,0)
    this.size = 0;
    this.head.next = this.tail;
    this.tail.prev = this.head;
}

DoubleList.prototype.addLast = function(x) {
    x.prev = this.tail.prev;
    x.next = this.tail;
    this.tail.prev.next = x
    this.tail.prev = x;
    this.size ++;
}

DoubleList.prototype.remove = function(x) {
    x.prev.next = x.next;
    x.next.prev = x.prev;
    this.size--;
}

DoubleList.prototype.removeFirst = function() {
    if (this.head.next == this.tail)
        return null;
    var first = this.head.next;
    this.remove(first);
    return first;
};

DoubleList.prototype.size = function() {
    return this.size;
};


/**
 * 实现Least Recently Cache
 * @param {number} capacity
 */
var LRUCache = function(capacity) {
 this.map = new Map();
    this.cache = new DoubleList();
    this.cap = capacity;
    this.makeRecently = function(key) {
        let x = this.map.get(key);
        this.cache.remove(x);
        this.cache.addLast(x);
    }
    this.addRecently = function(key, val) {
        let x = new Node(key, val);
        this.cache.addLast(x);
        this.map.put(key, x);
    }
    this.addRecently = function(key, val) {
        let x = new Node(key, val);
        this.cache.addLast(x);
        this.map.set(key, x);
    };
    this.deleteKey = function(key) {
        let x = this.map.get(key);
        this.cache.remove(x);
        this.map.delete(key);
    }
    this.removeLeastRecently = function() {
        let deletedNode = this.cache.removeFirst();
        let deletedKey = deletedNode.key
        this.map.delete(deletedKey)
    }
};

/** 
 * @param {number} key
 * @return {number}
 */
LRUCache.prototype.get = function(key) {
    if(!this.map.has(key)) {
        return -1;
    }
    this.makeRecently(key);
    return this.map.get(key).val;
};

/** 
 * @param {number} key 
 * @param {number} value
 * @return {void}
 */
LRUCache.prototype.put = function(key, val) {
 if(this.map.has(key)) {
        this.deleteKey(key);
        this.addRecently(key, val);
        return
    }
    if(this.cap === this.cache.size) {
        this.removeLeastRecently();
    }
    this.addRecently(key, val)
};