릿코드 623. Add One Row to Tree 코틀린

노드에서 해당댑스진입해서 사이에 해당숫자 끼워넣기
레프트일경우 다음숫자는 레프트에,라이트는 라이트,반대쪽은 널


정답

class Solution {
    fun addOneRow(root: TreeNode?, `val`: Int, depth: Int): TreeNode? {
        if (depth==1){
            val newLeftNode=TreeNode(`val`)
            newLeftNode.left=root
            return newLeftNode
        }
        return nodeInsert(root, `val`, depth-2)
    }
}
fun nodeInsert(curNode: TreeNode?, `val`:Int, curDepth: Int ):TreeNode{
    if (curNode==null){
        throw IllegalArgumentException()
    }
    val newNode = TreeNode(curNode.`val`)

    if (curDepth==0){
        val newLeftNode=TreeNode(`val`)
        newLeftNode.left=curNode.left
        newNode.left = newLeftNode

        val newRightNode=TreeNode(`val`)
        newRightNode.right=curNode.right
        newNode.right = newRightNode
        return newNode
    }
    if(curNode.left!=null){
        newNode.left=nodeInsert(curNode.left,`val`,curDepth-1)
    }
    if(curNode.right!=null){
        newNode.right=nodeInsert(curNode.right,`val`,curDepth-1)
    }
    return newNode
}