You are given the root
of a binary tree containing digits from 0
to 9
only.
Each roottoleaf path in the tree represents a number.
 For example, the roottoleaf path
1 > 2 > 3
represents the number123
.
Return the total sum of all roottoleaf numbers. Test cases are generated so that the answer will fit in a 32bit integer.
A leaf node is a node with no children.
Example 1:
1
/ \
2 3
Input: root = [1,2,3]
Output: 25
Explanation:
The roottoleaf path 1>2 represents the number 12.
The roottoleaf path 1>3 represents the number 13.
Therefore, sum = 12 + 13 = 25.
Example 2:
4
/ \
9 0
/ \
5 1
Input: root = [4,9,0,5,1]
Output: 1026
Explanation:
The roottoleaf path 4>9>5 represents the number 495.
The roottoleaf path 4>9>1 represents the number 491.
The roottoleaf path 4>0 represents the number 40.
Therefore, sum = 495 + 491 + 40 = 1026.
Constraints:
 The number of nodes in the tree is in the range
[1, 1000]
. 0 <= Node.val <= 9
 The depth of the tree will not exceed
10
.

