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# [129. Sum Root to Leaf Numbers](https://leetcode.com/problems/sum-root-to-leaf-numbers/)
## 题目
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.
## 题目大意
给定一个二叉树它的每个结点都存放一个 0-9 的数字每条从根到叶子节点的路径都代表一个数字。例如从根到叶子节点路径 1->2->3 代表数字 123。计算从根到叶子节点生成的所有数字之和。说明: 叶子节点是指没有子节点的节点。
## 解题思路
- 这一题是第 257 题的变形题,第 257 题要求输出每条从根节点到叶子节点的路径,这一题变成了把每一个从根节点到叶子节点的数字都串联起来,再累加每条路径,求出最后的总和。实际做题思路基本没变