LinkedList-Kotlin

class Node<T>(var data: T, var nextNode: Node<T>? = null)

class LinkedList<T> {
    var size: Int = 0
    var head: Node<T>? = null

    //O(1)
    fun insertStart(data: T) {
        size += 1
        val newNode = Node(data = data)
        head?.let {
            newNode.nextNode = head
            head = newNode
        } ?: run {
            head = newNode
        }
    }

    //O(n)
    fun insertEnd(data: T) {
        size += 1
        val newNode = Node(data = data)
        var actualNode = head
        while (actualNode?.nextNode != null) {
            actualNode = actualNode.nextNode
        }
        actualNode!!.nextNode = newNode
    }

    //O(n)
    fun remove(data:T){
        if (head == null){
            return
        }
        size -=1
        var currentNode = head
        var prevNode:Node<T>? = null
        while (currentNode?.data != data){
            prevNode = currentNode
            currentNode = currentNode?.nextNode

        }
        if (prevNode == null){
            head = currentNode!!.nextNode
        }else{
            prevNode.nextNode = currentNode!!.nextNode
        }
    }

    //O(1)
    fun size(): Int {
        return size
    }

    //O(n)
    fun size2(): Int {
        var actualNode = head
        var size = 0

        while (actualNode != null) {
            size += 1
            actualNode = actualNode.nextNode
        }
        return size
    }


    fun traverseList() {
        var actualNode = head
        while (actualNode?.nextNode != null) {
            println("${actualNode.data}")
            actualNode = actualNode.nextNode
        }
        println("${actualNode?.data}")
    }
}

fun main(args: Array<String>) {

    val list = LinkedList<Int>()
    val listStr = LinkedList<String>()

    listStr.insertStart("1")
    listStr.insertStart("12")
    listStr.insertStart("31")
    listStr.insertStart("44")
    listStr.traverseList()

    list.insertStart(12)
    list.insertStart(122)
    list.insertStart(3)
    list.insertEnd(31)
    list.insertEnd(32)
    list.traverseList()

    println("size=>${list.size()}")

    list.remove(12)
    list.remove(3)
    list.remove(122)
    list.remove(31)
    list.remove(32)

    println("size=>${list.size()}")

}