Queue
Unlike stack, a queue works on First in First Out(FIFO) principle. Two main operations are done on a queue; enqueue and dequeue.
To enqueue involves adding item to the back of queue while to dequeue involves removing front item in queue.
Linkedlist as storage
Implementing a queue using linkedlist;
1.The head of list is the head(front) of queue
2.The insertLast method is used to enqueue
3.The removeFirst method is used to dequeue
Implemetation
1.Create node and queue class
class Node {
constructor(data, next = null) {
this.data = data;
this.next = next;
}
}
class Queue {
constructor() {
this.head = null;
this.tail = null;
}
//add methods
}
Our queue has a head(front) and tail(back) item.
2.Add methods to our queue class to perform enqueue, dequeue and peek
Enqueue
//add item to queue
enqueue(data) {
let node = new Node(data);
//if empty, set new node as head and tail
if (this.tail == null) {
this.head = node;
this.tail = node;
return;
}
//add node as last item in queue
this.tail.next = node;
//set node as tail
this.tail = node;
}
Dequeue
//remove item from queue
dequeue() {
//if empty, do nothing
if (this.head == null) {
return;
}
//remove curent head and set head to next item in queue
this.head = this.head.next;
// set tail to null if queue is emptied
if (this.head == null) {
this.tail = null;
}
}
peek
//return first item in queue
peek() {
if (this.head == null) {
return "Queue is empty";
}
return this.head.data;
}
I'll be implementing a queue with arrays next, stay tuned.
Happy Coding! đź‘Ż
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