#coding=utf-8
class Node(object):
  """節(jié)點類"""
  def __init__(self, elem=-1, lchild=None, rchild=None):
    self.elem = elem
    self.lchild = lchild
    self.rchild = rchild
class Tree(object):
  """樹類"""
  def __init__(self):
    self.root = Node()
    self.myQueue = []
  def add(self, elem):
    """為樹添加節(jié)點"""
    node = Node(elem)
    if self.root.elem == -1: # 如果樹是空的，則對根節(jié)點賦值
      self.root = node
      self.myQueue.append(self.root)
    else:
      treeNode = self.myQueue[0] # 此結(jié)點的子樹還沒有齊。
      if treeNode.lchild == None:
        treeNode.lchild = node
        self.myQueue.append(treeNode.lchild)
      else:
        treeNode.rchild = node
        self.myQueue.append(treeNode.rchild)
        self.myQueue.pop(0) # 如果該結(jié)點存在右子樹，將此結(jié)點丟棄。
  def front_digui(self, root):
    """利用遞歸實現(xiàn)樹的先序遍歷"""
    if root == None:
      return
    print root.elem,
    self.front_digui(root.lchild)
    self.front_digui(root.rchild)
  def middle_digui(self, root):
    """利用遞歸實現(xiàn)樹的中序遍歷"""
    if root == None:
      return
    self.middle_digui(root.lchild)
    print root.elem,
    self.middle_digui(root.rchild)
  def later_digui(self, root):
    """利用遞歸實現(xiàn)樹的后序遍歷"""
    if root == None:
      return
    self.later_digui(root.lchild)
    self.later_digui(root.rchild)
    print root.elem,
  def front_stack(self, root):
    """利用堆棧實現(xiàn)樹的先序遍歷"""
    if root == None:
      return
    myStack = []
    node = root
    while node or myStack:
      while node:           #從根節(jié)點開始，一直找它的左子樹
        print node.elem,
        myStack.append(node)
        node = node.lchild
      node = myStack.pop()      #while結(jié)束表示當(dāng)前節(jié)點node為空，即前一個節(jié)點沒有左子樹了
      node = node.rchild         #開始查看它的右子樹
  def middle_stack(self, root):
    """利用堆棧實現(xiàn)樹的中序遍歷"""
    if root == None:
      return
    myStack = []
    node = root
    while node or myStack:
      while node:           #從根節(jié)點開始，一直找它的左子樹
        myStack.append(node)
        node = node.lchild
      node = myStack.pop()      #while結(jié)束表示當(dāng)前節(jié)點node為空，即前一個節(jié)點沒有左子樹了
      print node.elem,
      node = node.rchild         #開始查看它的右子樹
  def later_stack(self, root):
    """利用堆棧實現(xiàn)樹的后序遍歷"""
    if root == None:
      return
    myStack1 = []
    myStack2 = []
    node = root
    myStack1.append(node)
    while myStack1:          #這個while循環(huán)的功能是找出后序遍歷的逆序，存在myStack2里面
      node = myStack1.pop()
      if node.lchild:
        myStack1.append(node.lchild)
      if node.rchild:
        myStack1.append(node.rchild)
      myStack2.append(node)
    while myStack2:             #將myStack2中的元素出棧，即為后序遍歷次序
      print myStack2.pop().elem,
  def level_queue(self, root):
    """利用隊列實現(xiàn)樹的層次遍歷"""
    if root == None:
      return
    myQueue = []
    node = root
    myQueue.append(node)
    while myQueue:
      node = myQueue.pop(0)
      print node.elem,
      if node.lchild != None:
        myQueue.append(node.lchild)
      if node.rchild != None:
        myQueue.append(node.rchild)
if __name__ == '__main__':
  """主函數(shù)"""
  elems = range(10)      #生成十個數(shù)據(jù)作為樹節(jié)點
  tree = Tree()     #新建一個樹對象
  for elem in elems:
    tree.add(elem)      #逐個添加樹的節(jié)點
  print '隊列實現(xiàn)層次遍歷:'
  tree.level_queue(tree.root)
  print '\n\n遞歸實現(xiàn)先序遍歷:'
  tree.front_digui(tree.root)
  print '\n遞歸實現(xiàn)中序遍歷:'
  tree.middle_digui(tree.root)
  print '\n遞歸實現(xiàn)后序遍歷:'
  tree.later_digui(tree.root)
  print '\n\n堆棧實現(xiàn)先序遍歷:'
  tree.front_stack(tree.root)
  print '\n堆棧實現(xiàn)中序遍歷:'
  tree.middle_stack(tree.root)
  print '\n堆棧實現(xiàn)后序遍歷:'
  tree.later_stack(tree.root)