queues.md

Queues

Array

class Queue {
  constructor() {
    this.queue = []
  }

  enqueue(element) {
    this.queue.push(element)
  }

  dequeue() {
    if (this.isEmpty()) return 'Queue is empty'
    return this.queue.shift()
  }

  peek() {
    if (this.isEmpty()) return 'Queue is empty'
    return this.queue[0]
  }

  // helper method
  isEmpty() {
    return !this.queue.length
  }
}

---

Linked list

class Node {
  constructor(next, value) {
    this.next = next
    this.value = value
  }
}

class Queue {
  constructor() {
    this.queue = null
  }

  enqueue(element) {
    let head = this.queue
    let newNode = new Node(null, element)

    if (!head) {
      this.queue = newNode
    } else {
      let traverseNode = head
      while (traverseNode.next) {
        traverseNode = traverseNode.next
      }
      traverseNode = newNode
    }
  }

  dequeue() {
    let head = this.queue

    if (!head) return 'Queue is empty!'

    this.queue = head.next
    return head.value
  }

  peek() {
    if(!this.queue) return 'Queue is empty!'
    return this.queue.value
  }
}