first commit

Author: pinglu85

data-structures/Queue.js

@@ -0,0 +1,74 @@
+class Node {
+  constructor(value, next = null) {
+    this.value = value;
+    this.next = next;
+  }
+}
+
+class Queue {
+  #head;
+  #tail;
+  #length;
+
+  constructor() {
+    this.#head = null;
+    this.#tail = null;
+    this.#length = 0;
+  }
+
+  /**
+   * Adds an element to the end of the queue.
+   * @param {*} value The element to be added.
+   * @returns {number} The new length of the queue.
+   */
+  enqueue(value) {
+    const node = new Node(value);
+
+    if (this.isEmpty()) {
+      this.#head = node;
+      this.#tail = node;
+    } else {
+      this.#tail.next = node;
+      this.#tail = node;
+    }
+
+    return ++this.#length;
+  }
+
+  /**
+   * Removes the element at the front of the queue.
+   * @returns {*} The element at the front of the queue.
+   */
+  dequeue() {
+    if (this.isEmpty()) {
+      return null;
+    }
+
+    const currHead = this.#head;
+    this.#head = currHead.next;
+    currHead.next = null;
+    this.#length--;
+
+    if (this.isEmpty()) {
+      this.#tail = null;
+    }
+
+    return currHead.value;
+  }
+
+  /**
+   * Checks if the queue is empty.
+   * @returns {boolean} Whether the queue is empty.
+   */
+  isEmpty() {
+    return this.#length === 0;
+  }
+
+  /**
+   * Gets the number of elements in the queue.
+   * @returns {number} The number of elements in the queue.
+   */
+  get length() {
+    return this.#length;
+  }
+}