构建二叉树(swift)

publicclassALTree<T: Comparable> {
    var key : T?
    var left : ALTree?
    var right : ALTree?
   
    func addNode(key : T) {
        if (self.key== nil) {
            self.key= key
            return
        }
       
        if (key < self.key) {
            if (self.left!= nil) {
                left!.addNode(key)
            } else {
                var leftChild : ALTree = ALTree()
                leftChild.key= key
                self.left= leftChild
            }
        }
       
        if (key > self.key) {
            if (self.right!= nil) {
                right!.addNode(key)
            } else {
                var rightChild : ALTree = ALTree()
                rightChild.key= key
                self.right= rightChild
            }
        }
    }

}

letnumberList : Array<Int> = [8,2,10,9,11,1,7]
varroot = ALTree<Int>()
fornumber in numberList {
    root.addNode(number)
}

println(root)