# leetcode: 129. Sum Root to Leaf Numbers

Medium.

## Problem

```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.```

## AC

```# 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):
res = []
self.dfs(res, root, '')
return sum(list(map(int, res)))
def dfs(self, res, root, path):
if not root:
return
if not root.left and not root.right:
res.append(path+str(root.val))
else:
self.dfs(res, root.left, path+str(root.val))
self.dfs(res, root.right, path+str(root.val))```

0 条评论