ARTS 009

class Solution {
    fun largestValues(root: TreeNode?): List<Int> {
        val result = mutableListOf<Int>()

        if (root == null) return result

        val queue = LinkedList<TreeNode>()
        queue.add(root!!)
        while (queue.size > 0) {
            val curArray = arrayListOf<TreeNode>()
            var max = Int.MIN_VALUE
            while (queue.size > 0) {
                val element = queue.pop()
                curArray.add(element)
                max = max.coerceAtLeast(element.`val`)
            }
            result.add(max)

            for (element in curArray) {
                if (element.left != null) {
                    queue.add(element.left!!)
                }

                if (element.right != null) {
                    queue.add(element.right!!)
                }
            }        
        }
        return result
    }
}