o

class TreeNode:
  def __init__(self, val):
    self.val = val
    self.children = []

def serialize(root):
  def helper(root, ret):
    ret.append(str(root.val))
    for child in root.children:
      helper(child, ret)
    ret.append('#')

  ret = []
  if not root: return ""
  helper(root, ret)
  return ','.join(ret)

def deserialize(s):
  def helper(s, idx):
    start = idx
    while idx<len(s) and s[idx]!=',':
      idx+=1
    c = s[start:idx]
    idx+=1
    if c=='#':
      return None, idx

    root = TreeNode(int(c))
    child, idx = helper(s, idx)
    while child is not None:
      root.children.append(child)
      child, idx = helper(s, idx)
    return root, idx

  root, i = helper(s, 0)
  return root

print serialize(deserialize("1,2,3,#,4,5,#,#,#,6,#,7,8,#,9,#,10,#,11,#,#,#"))