class BinaryTreeNote{
 
 var value:String
 var leftChild:BinaryTreeNote?
 var rightChild:BinaryTreeNote?
 
 init(_ value:String) {
 self.value = value
 }
 
}
 
 
class BinaryTreeHelper{
 
 var array:[String]
 var index = -1
 
 init(_ array:[String]) {
 self.array = array
 }
 
 //创建二叉树
 func createTree() -> BinaryTreeNote? {
 
 self.index = self.index + 1
 if index < self.array.count && index >= 0 {
 
  let value = self.array[index]
  
  if value == "" {
  return nil
  } else {
  let note = BinaryTreeNote(value)
  note.leftChild = createTree()
  note.rightChild = createTree()
  return note
  }
 }
 return nil;
 }
 
 //先序遍历二叉树
 func preOrderTraverse(_ note:BinaryTreeNote?){
 
 if note == nil {
  print("#")
  return
 }
 print(note!.value)
 preOrderTraverse(note!.leftChild)
 preOrderTraverse(note!.rightChild)
 }
 
 //中序遍历二叉树
 func inOrderTraverse (_ note: BinaryTreeNote?) {
 if note == nil {
  print("#")
  return
 }
 inOrderTraverse(note!.leftChild)
 print(note!.value)
 inOrderTraverse(note!.rightChild)
 }
 
 //后序遍历二叉树
 func afterOrderTraverse (_ note: BinaryTreeNote?) {
 if note == nil {
  print("#")
  return
 }
 afterOrderTraverse(note!.leftChild)
 afterOrderTraverse(note!.rightChild)
 print(note!.value)
 }
 
 //层次遍历二叉树
 func levelOrder(_ root: BinaryTreeNote?){
 
 var result = [[BinaryTreeNote]]()
 var level = [BinaryTreeNote]()
 
 level.append(root!)
 while level.count != 0 {
  result.append(level)
  var nextLevel = [BinaryTreeNote]()
  for node in level {
  if let leftNode = node.leftChild {
   nextLevel.append(leftNode)
  }
  if let rightNode = node.rightChild {
   nextLevel.append(rightNode)
  }
  }
  level = nextLevel
 }
 
 let ans = result.map { $0.map { $0.value }}
 print(ans)
 }
 
 
}