Intro
Last time, we added the dequeue
method.
I hope you learned something about the concept of a Queue and tried your best to implement it on your own.
Thoughts about the Queue 💭
We implemented the Queue using a Singly Linked List.
The Queue data structure is a very important concept, because we use it all the time.
The Queue is based on the "First In, First Out"-Principle, meaning the first node that goes into the queue will later be the first node, that goes out of the queue.
Examples in real life: people who want to pay in a store, the tasks of a printer.
- Access:
O(N)
- Search:
O(N)
- Insert:
O(1)
- Remove:
O(1)
Final Implementation 📝
Our Queue has these methods:
-
enqueue
, to add a node to the end of the queue -
dequeue
, to remove a node from the start of the queue
class Node {
constructor(value) {
this.value = value;
this.next = null;
}
}
class Queue {
constructor() {
this.length = 0;
this.start = null;
this.end = null;
}
enqueue(value) {
const newNode = new Node(value);
if (!this.length) {
this.start = newNode;
this.end = newNode;
} else {
this.end.next = newNode;
this.end = newNode;
}
this.length += 1;
return newNode;
}
dequeue() {
if (!this.length) {
return null;
} else {
const nodeToRemove = this.start;
this.start = this.start.next;
nodeToRemove.next = null;
if (this.length === 1) {
this.end = null;
}
this.length -= 1;
return nodeToRemove;
}
}
}
Further Reading 📖
Questions ❔
- Can you implement a new method
peek
, that returns the start node, without removing it?
Next Part ➡️
We will compare the Data Structures we've built so far.
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