kotlin实现二叉排序树（binary sort tree）的插入

fun main(args: Array<String>) {
    val nodes: IntArray = intArrayOf(8, 3, 10, 1, 6, 14, 4, 7, 13)
    val binaryTree = BinaryTree()
    nodes.forEach { binaryTree.insert(it) }
}
class BinaryTree {
    var root: Node? = null
    private fun insertNode(node: Node, newNode: Node) {
        if (newNode.key < node.key) {
            if (node.left == null) {
                node.left = newNode
            } else {
                insertNode(node.left!!, newNode);
            }
        } else {
            if (node.right == null) {
                node.right = newNode
            } else {
                insertNode(node.right!!, newNode)
            }
        }
    }
    fun insert(key: Int) {
        val newNode = Node(key)
        if (root == null) {
            root = newNode
        } else {
            insertNode(root!!, newNode)
        }
    }
}
class Node(var key: Int) {
    var left: Node? = null
    var right: Node? = null
}