# [Solved] You are given the root of a binary tree containing digits from 0 to 9 only. Each root-to-leaf path in the tree represents a number. ## Question

You are given the `root` of a binary tree containing digits from `0` to `9` only.

Each root-to-leaf path in the tree represents a number.

• For example, the root-to-leaf path `1 -> 2 -> 3` represents the number `123`.

Return the total sum of all root-to-leaf numbers. Test cases are generated so that the answer will fit in a 32-bit integer.

leaf node is a node with no children.

Example 1:

```Input: root = [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: root = [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`.
```

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`.

## Python Solution

```def traverse(root,l,prev):
if root==None:return
if root.left==None and root.right==None:
l.append(int(prev+str(root.val)))
traverse(root.left,l,prev+str(root.val))
traverse(root.right,l,prev+str(root.val))

class Solution:
def sumNumbers(self, root: TreeNode) -> int:
l = []
traverse(root,l,'')
return sum(l)```