关于二叉树的算法题目

####python的二叉树结构
class Tree(object):
def init(self, data=None, left=None, right=None):
self.data = data
self.left = left
self.right = right

####构造一棵二叉树

####3种遍历方式
def preTraverse(root):
if root == None:
return
print root.data
preTraverse(root.left)
preTraverse(root.right)

def middleTraverse(root):
  if root == None:
      return
  middleTraverse(root.left)
  print root.data
  middleTraverse(root.right)

def afterTraverse(root):
  if root == None:
      return
  afterTraverse(root.left)
  afterTraverse(root.right)
  print root.data

if __name__ == "__main__":
  root = Tree("A",Tree("B", Tree("D"),Tree("E")), Tree("C", Tree("F"), Tree("G")))
  print '-------pre--------'
  preTraverse(root)
  print '-------middle-----'
  middleTraverse(root)
  print '-------end--------'
  afterTraverse(root)