class BinNode( ):
  def __init__( self, val ):
    self.lchild = None
    self.rchild = None
    self.value = val
binNode1 = BinNode( 1 )
binNode2 = BinNode( 2 )
binNode3 = BinNode( 3 )
binNode4 = BinNode( 4 )
binNode5 = BinNode( 5 )
binNode6 = BinNode( 6 )
binNode1.lchild = binNode2
binNode1.rchild = binNode3
binNode2.lchild = binNode4
binNode2.rchild = binNode5
binNode3.lchild = binNode6

'''
先序遍历二叉树
'''
def bin_tree_pre_order_traverse( root, visit_func ):
  s = Stack()
  s.push( root )
  while not s.is_empty():
    node = s.pop()
    visit_func( node )
    if node.rchild:
      s.push( node.rchild )
    if node.lchild:
      s.push( node.lchild )

'''
中序遍历二叉树
'''
def bin_tree_in_order_traverse( root, visit_func ):
  s = Stack()
  node = root
  while node or not s.is_empty():
    if node:
      s.push( node )
      node = node.lchild
    else:
      node = s.pop()
      visit_func( node )
      node = node.rchild

'''
后序遍历二叉树
'''
def bin_tree_post_order_traverse( root, visit_func ):
  s1 = Stack()
  s2 = Stack()
  s1.push( root )
  while not s1.is_empty():
    node = s1.pop()
    s2.push( node )
    if node.lchild:
      s1.push( node.lchild )
    if node.rchild:
      s1.push( node.rchild )
  while not s2.is_empty():
    visit_func( s2.pop() )

def bin_tree_post_order_traverse2( root, visit_func ):
  curr = root
  prev = None
  s = Stack()
  s.push( curr )
  while not s.is_empty():
    curr = s.peek()
    if ( not curr.lchild and not curr.rchild ) or ( prev and ( prev == curr.lchild or prev == curr.rchild ) ):
      visit_func( curr )
      s.pop()
　　　　　　　prev = curr
    else:
      if curr.rchild:
        s.push( curr.rchild )
      if curr.lchild:
        s.push( curr.lchild )

def bin_tree_level_traverse( root, visit_func ):
  queue = Queue()
  queue.enqueue( root )
  while not queue.is_empty():
    node = queue.dequeue().value
    visit_func( node )
    if node.lchild:
      queue.enqueue( node.lchild )
    if node.rchild:
      queue.enqueue( node.rchild )