릿코드 2816. Double a Number Represented as a Linked List 코틀린

그냥 다 뽑아낸다음 x2하고 스트링으로 바꿔서 한자리씩 노드생성하기

정답

class Solution {
    fun doubleIt(head: ListNode?): ListNode? {
        var curNode=requireNotNull(head)
        var tempValue=""
        while (true){
            tempValue+=curNode.`val`.toString()
            if (curNode.next==null){
                break
            }
            curNode=curNode.next!!
        }
        val resStr = (tempValue.toBigDecimal() * BigDecimal(2)).toString()
        var prevNode=ListNode(resStr[0].digitToInt())
        val resNode=prevNode
        for (i in resStr.substring(1,resStr.length)){
            val tempNode=ListNode(i.digitToInt())
            prevNode.next=tempNode
            prevNode=tempNode
        }
        return resNode

    }
}

class ListNode(var `val`: Int) {
         var next: ListNode? = null
}