# Insert node at end of linked list in kotlin

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

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

```
// Kotlin Program for
// Insert linked list element at end position
// Linked list node
class LinkNode
{
var data: Int;
var next: LinkNode ? ;
constructor(data: Int)
{
this.data = data;
this.next = null;
}
}
class SingleLL
{
var head: LinkNode ? ;
constructor()
{
this.head = null;
}
// Add new node at the end of linked list
fun addNode(value: Int): Unit
{
// Create new node
val node: LinkNode = 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
fun 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");
}
}
}
fun main(args: Array < String > ): Unit
{
val sll: SingleLL = 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.

```
// Kotlin Program for
// Insert linked list element at end position set B
// Linked list node
class LinkNode
{
var data: Int;
var next: LinkNode ? ;
constructor(data: Int)
{
this.data = data;
this.next = null;
}
}
class SingleLL
{
var head: LinkNode ? ;
var tail: LinkNode ? ;
constructor()
{
this.head = null;
this.tail = null;
}
// Add new node at the end of linked list
fun addNode(value: Int): Unit
{
// Create a new node
val node: LinkNode = LinkNode(value);
if (this.head == null)
{
this.head = node;
}
else
{
this.tail?.next = node;
}
this.tail = node;
}
// Display linked list element
fun 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");
}
}
fun main(args: Array < String > ): Unit
{
val sll: SingleLL = 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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