0129-sum-root-to-leaf-numbers.adoc

129. Sum Root to Leaf Numbers

{leetcode}/problems/sum-root-to-leaf-numbers/[LeetCode - Sum Root to Leaf Numbers^]

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.

解题分析

这道题和 112. Path Sum 类似。

找到所有路径，父级乘以10，再加当前节点，最后到叶子节点时，加入到总和中。

思考题

1. 尝试使用中根遍历和后跟遍历的解法。

2. 目前解法是会用了实例变量，能否取去掉？

参考资料

1. 3中解法：递归先序、非递归先序、层序 - 求根到叶子节点数字之和 - 力扣（LeetCode）

2. 详细通俗的思路分析，多解法 - 求根到叶子节点数字之和 - 力扣（LeetCode）

link:{sourcedir}/_0129_SumRootToLeafNumbers.java[role=include]