Simple Swift AVL Tree

AVLTree.swift

//
//  AVLTree.swift
//  AVLTree-Swift
//
//  Created by Arnaud Schildknecht on 22/05/15.
//  Copyright (c) 2015 Arnaud Schildknecht. All rights reserved.
//

class AVLTree<T: Comparable> {
  
  var data: T?
  var left: AVLTree?
  var right: AVLTree?
  
  init() {
  }
  
  func addValue(value: T) {
    if (self.data == nil) {
      self.data = value
    }
    else {
      add(value)
    }
  }
  
  private func add(value: T) {
    if (value < self.data) {
      if (self.left != nil) {
        self.left?.addValue(value)
      }
      else {
        self.left = AVLTree<T>()
        self.left?.data = value
      }
      
    }
    else {
      if (self.right != nil) {
        self.right?.addValue(value)
      }
      else {
        self.right = AVLTree<T>()
        self.right?.data = value
      }
    }
  }
  
  func inOrder() -> [T] {
    var datas = Array<T>()
    
    inOrder(self, datas: &datas)
    return datas
  }
  
  private func inOrder(root: AVLTree<T>?, inout datas: [T]) {
    if (root != nil) {
      inOrder(root?.left, datas: &datas)
      datas.append((root?.data)!)
      inOrder(root?.right, datas: &datas)
    }
  }
  
  func preOrder() -> [T] {
    var datas = Array<T>()
    
    preOrder(self, datas: &datas)
    return datas
  }
  
  private func preOrder(root: AVLTree<T>?, inout datas: [T]) {
    if (root != nil) {
      datas.append((root?.data)!)
      preOrder(root?.left, datas: &datas)
      preOrder(root?.right, datas: &datas)
    }
  }
  
  func postOrder() -> [T] {
    var datas = Array<T>()
    
    postOrder(self, datas: &datas)
    return datas
  }
  
  private func postOrder(root: AVLTree<T>?, inout datas: [T]) {
    if (root != nil) {
      postOrder(root?.left, datas: &datas)
      postOrder(root?.right, datas: &datas)
      datas.append((root?.data)!)
    }
  }
  
}