题解 | #二叉树根节点到叶子节点的所有路径和#
二叉树根节点到叶子节点的所有路径和
http://www.nowcoder.com/practice/185a87cd29eb42049132aed873273e83
helper函数：给定当前结点root和当前的路径和s，返回以root为根节点的树的路径和。
class Solution:
def sumNumbers(self , root ):
# write code here
def helper(root, s):
if not root:
return 0
s = 10*s + root.val
if not root.left and not root.right:
return s
return helper(root.left, s) + helper(root.right, s)
return helper(root, 0)
