[LeetCode] 129. Sum Root to Leaf Numbers

轉自LeetCode

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.

For example,

    1
   / \
  2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

<Solution>

這題是典型的 DFS 題目

首先先看 recursive 的寫法

思路不困難，就是歷遍然後求和

code 如下

接著看 iteration 的寫法

不同的地方是使用一個 stack 來完成歷遍

code 如下