릿코드 1026. Maximum Difference Between Node and Ancestor 코틀린

bfs돌리면서,현재위치에서 연결된 모든트리들의 값을 계산하면서 max치면될듯
미리 해당위치에서 하위의 맥스값계산하는함수 만들어두면편할듯

정답

class Solution {
    fun maxAncestorDiff(root: TreeNode?): Int {
        //val maxValue=maxValueNodeCal(root,root!!.`val`)
        var maxValue=0
        val queue:Queue<TreeNode> =LinkedList()
        
        queue.add(root)
        while (queue.isNotEmpty()){
            val tempNode=queue.poll()
            if (tempNode.right!=null) {
                queue.add(tempNode.right)
            }
            if (tempNode.left!=null) {
                queue.add(tempNode.left)
            }
            
            maxValue=max(maxValue,maxValueNodeCal(tempNode,tempNode.`val`))
        }
        

        
        return maxValue
    }
    fun maxValueNodeCal(curNode: TreeNode?,rootNodeValue:Int):Int{
        var maxValue=0
        if (curNode==null){
            throw IllegalArgumentException()
        }
            
        if(curNode.left!=null){
            val leftValue=( maxValueNodeCal(curNode.left,rootNodeValue))
            maxValue= max(maxValue, abs(leftValue))
        }
        if(curNode.right!=null){
            val rightValue=( maxValueNodeCal(curNode.right,rootNodeValue))
            maxValue= max(maxValue, abs(rightValue))
        }
        maxValue= max(maxValue, abs(rootNodeValue-curNode.`val`))
        return maxValue
    }
}