m0129.md

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.

Source Code

1. re-construct from one BFS traversal
2. enumerate-root-to-leaf-numbers