Data Structures Decoded: Singly Linked Lists IV

Photo by Luca Bravo on Unsplash

Data structures: the other cornerstone of a competent software engineer. This is why I’m compiling all my research and work on the topic in a series of articles titled Data Structures Decoded.

Previously on Data Structures Decoded…

In the second part of our look at Singly Linked Lists, we created a .shift() instance method.

In today’s article, we’ll be exploring how to add an .unshift() function to our Singly Linked List class.

Let’s Unshift Gears

Here’s the pseudocode:

• The function should accept a value
• Create a new node using the value passed to the function
• If there is no head property on the list, set the head and tail to be newly created node
• Otherwise, set the newly created node’s next property to be the current head property on the list
• Set the head property on the list to be that newly created node
• Increment the length of the list by 1
• Return the linked list

And for the main event…

unshift(val) {
    let newNode = new Node(val); 
    if (!this.head) {
        this.head = newNode; 
        this.tail = this.head; 
    } else { 
        newNode.next = this.head; 
        this.head = newNode; 
    }
    this.length++; 
    return this; 
}

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