# 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.

# For example,

#     1
#    / \
#   2   3

# The root-to-leaf path 1->2 represents the number 12.
# The root-to-leaf path 1->3 represents the number 13.

# Return the sum = 12 + 13 = 25. 

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

class Solution:
    def __init__(self):
        self.res = 0
        
    def sumNumbers(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        def dfs(current, node):
            if node is None:
                return
            current = current * 10 + node.val
            if node.left is None and node.right is None:
                self.res += current
            else:
                dfs(current, node.left)
                dfs(current, node.right)
        dfs(0, root)
        return self.res
