릿코드 129. Sum Root to Leaf Numbers 코틀린

그냥 재귀로 노드탐색하면서 val텍스트로 저장하다가 리프면 값으로 변환해서 리턴
리프아니면 레프트나 라이트에서 값받아오고

정답

class Solution {
    fun sumNumbers(root: TreeNode?): Int {
        return leftLeafSearch(root,"")
    }
}
fun leftLeafSearch(root1: TreeNode?, reqStr:String ):Int{
    if (root1==null){
        throw IllegalArgumentException()
    }
    var valueString=reqStr+root1.`val`.toString()
    if (root1.left==null && root1.right==null){
        return valueString.toInt()
    }
    var res=0
    if(root1.left!=null){
        res+=leftLeafSearch(root1.left,valueString)
    }
    if(root1.right!=null){
        res+=leftLeafSearch(root1.right,valueString)
    }
    return res
}

노드클래스

class TreeNode(var `val`: Int) {
    var left: TreeNode? = null
    var right: TreeNode? = null
}