Insert node at end of linked list in scala

Write a program which is create and add linked list node at the end (tail, last) position in scala.

Suppose we are inserted the following (10, 20, 30 ,40 ,50) node in a sequence.

insert node at end of linked list
// Scala Program for
// Insert linked list element at end position Set A

// Linked list node
class LinkNode(var data: Int,
    var next: LinkNode)
{
    def this(data: Int)
    {
        this(data, null);
    }
}
class SingleLL(var head: LinkNode)
{
    def this()
    {
        this(null);
    }
    // Add new node at the end of linked list
    def addNode(value: Int): Unit = {
        // Create new node
        var node: LinkNode = new LinkNode(value);
        if (this.head == null)
        {
            this.head = node;
        }
        else
        {
            var temp: LinkNode = this.head;
            // find last node
            while (temp.next != null)
            {
                // Visit to next node
                temp = temp.next;
            }
            // Add node at last position
            temp.next = node;
        }
    }
    //Display all Linked List elements
    def display(): Unit = {
        if (this.head != null)
        {
            var temp: LinkNode = this.head;
            while (temp != null)
            {
                // Display node value
                print("  " + temp.data);
                // Visit to next node
                temp = temp.next;
            }
        }
        else
        {
            print("Empty Linked list\n");
        }
    }
}
object Main
{
    def main(args: Array[String]): Unit = {
        var sll: SingleLL = new SingleLL();
        // Linked list
        // 1 → 2 → 3 → 4 → 5 → 6 → 7 → 8 → NULL
        sll.addNode(1);
        sll.addNode(2);
        sll.addNode(3);
        sll.addNode(4);
        sll.addNode(5);
        sll.addNode(6);
        sll.addNode(7);
        sll.addNode(8);
        print(" Linked List \n");
        sll.display();
    }
}
 Linked List
  1  2  3  4  5  6  7  8

Time complexity of above program is O(n). We can optimize above algorithm using one extra pointer. Which is hold the reference of last node. Below are implementation of this logic.

// Scala Program for
// Insert linked list element at end position set B

// Linked list node
class LinkNode(var data: Int,
    var next: LinkNode)
{
    def this(data: Int)
    {
        this(data, null);
    }
}
class SingleLL(var head: LinkNode,
    var tail: LinkNode)
{
    def this()
    {
        this(null, null);
    }
    // Add new node at the end of linked list
    def addNode(value: Int): Unit = {
        // Create a new node
        var node: LinkNode = new LinkNode(value);
        if (this.head == null)
        {
            this.head = node;
        }
        else
        {
            this.tail.next = node;
        }
        this.tail = node;
    }
    // Display linked list element
    def display(): Unit = {
        if (this.head == null)
        {
            return;
        }
        var temp: LinkNode = this.head;
        // iterating linked list elements
        while (temp != null)
        {
            print(""+ temp.data + " → ");
            // Visit to next node
            temp = temp.next;
        }
        print(" NULL\n");
    }
}
object Main
{
    def main(args: Array[String]): Unit = {
        var sll: SingleLL = new SingleLL();
        // Linked list
        // 10 → 20 → 30 → 40 → 50 → NULL
        sll.addNode(10);
        sll.addNode(20);
        sll.addNode(30);
        sll.addNode(40);
        sll.addNode(50);
        print("Linked List \n");
        sll.display();
    }
}
Linked List 
10 → 20 → 30 → 40 → 50 →  NULL

Time complexity of above program is O(1).



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