human
Solve in Python:
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

Note: A leaf is a node with no children.

Example:

Input: [1,2,3]
    1
   / \
  2   3
Output: 25
Explanation:
The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.
Therefore, sum = 12 + 13 = 25.

Example 2:

Input: [4,9,0,5,1]
    4
   / \
  9   0
 / \
5   1
Output: 1026
Explanation:
The root-to-leaf path 4->9->5 represents the number 495.
The root-to-leaf path 4->9->1 represents the number 491.
The root-to-leaf path 4->0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
assistant
#Here is Python code to find the total sum of all root-to-leaf numbers.

# Definition for a binary tree node.
 # class TreeNode:
 #     def __init__(self, x):
 #         self.val = x
 #         self.left = None
 #         self.right = None
 
 class Solution:
     def sumNumbers(self, root):
         """
         :type root: TreeNode
         :rtype: int
         """
         if root is None:
             return 0
         ret = 0
         que = [root]
         while len(que) != 0:
             node = que.pop(0)
             if node.left is None and node.right is None:
                 ret += node.val
             if node.left:
                 node.left.val = node.val*10 + node.left.val
                 que.append(node.left)
             if node.right:
                 node.right.val = node.val*10 + node.right.val
                 que.append(node.right)
         return ret