先序遍历就行
def sumNumbers(self, root):
"""
:type root: TreeNode
:rtype: int
"""
def pre(root,pretotal):
if not root:
return 0
total = pretotal*10 + root.val
if not root.left and not root.right:
return total
return pre(root.left,total) + pre(root.right,total)
return pre(root,0)
