# Question

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.


# Solution

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
def sumNumbers(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if root is None:
return 0
return self.sumNode(0, root)

def sumNode(self, sums, node):
if node.left is None and node.right is None:
return sums + node.val
if node.left is not None:
node.left.val = node.val * 10 + node.left.val
sums = self.sumNode(sums, node.left)
if node.right is not None:
node.right.val = node.val * 10 + node.right.val
sums = self.sumNode(sums, node.right)
return sums