feat: add linkedlist_queue in js

codes/javascript/chapter_stack_and_queue/linkedlist_queue.js

@@ -0,0 +1,103 @@
+/**
+ * File: linkedlist_queue.js
+ * Created Time: 2022-12-20
+ * Author: S-N-O-R-L-A-X (snorlax.xu@outlook.com)
+ */
+
+const ListNode = require("../include/ListNode");
+
+/* 基于链表实现的队列 */
+class LinkedListQueue {
+    #front;
+    #rear;  // 头结点 #front ，尾结点 #rear 
+    #queSize = 0;
+
+    constructor() {
+        this.#front = null;
+        this.#rear = null;
+    }
+
+    /* 获取队列的长度 */
+    get size() {
+        return this.#queSize;
+    }
+
+    /* 判断队列是否为空 */
+    isEmpty() {
+        return this.size === 0;
+    }
+
+    /* 入队 */
+    offer(num) {
+        // 尾结点后添加 num
+        const node = new ListNode(num);
+        // 如果队列为空，则令头、尾结点都指向该结点
+        if (!this.#front) {
+            this.#front = node;
+            this.#rear = node;
+            // 如果队列不为空，则将该结点添加到尾结点后
+        } else {
+            this.#rear.next = node;
+            this.#rear = node;
+        }
+        this.#queSize++;
+    }
+
+    /* 出队 */
+    poll() {
+        const num = this.peek();
+        if (!this.#front) {
+            throw new Error("No element in queue!")
+        }
+        // 删除头结点
+        this.#front = this.#front.next;
+        this.#queSize--;
+        return num;
+    }
+
+    /* 访问队首元素 */
+    peek() {
+        if (this.size === 0)
+            throw new Error("No element in queue!");
+        return this.#front.val;
+    }
+
+    /* 将链表转化为 Array 并返回 */
+    toArray() {
+        let node = this.#front;
+        const res = new Array(this.size);
+        for (let i = 0; i < res.length; i++) {
+            res[i] = node.val;
+            node = node.next;
+        }
+        return res;
+    }
+}
+
+
+/* 初始化队列 */
+const queue = new LinkedListQueue();
+
+/* 元素入队 */
+queue.offer(1);
+queue.offer(3);
+queue.offer(2);
+queue.offer(5);
+queue.offer(4);
+console.log("队列 queue = " + queue.toArray());
+
+/* 访问队首元素 */
+const peek = queue.peek();
+console.log("队首元素 peek = " + peek);
+
+/* 元素出队 */
+const poll = queue.poll();
+console.log("出队元素 poll = " + poll + "，出队后 queue = " + queue.toArray());
+
+/* 获取队列的长度 */
+const size = queue.size;
+console.log("队列长度 size = " + size);
+
+/* 判断队列是否为空 */
+const isEmpty = queue.isEmpty();
+console.log("队列是否为空 = " + isEmpty);