sum-root-to-leaf-numbers.md

<p>Given a binary tree containing digits from <code>0-9</code> only, each root-to-leaf path could represent a number.</p>

<p>An example is the root-to-leaf path <code>1-&gt;2-&gt;3</code> which represents the number <code>123</code>.</p>

<p>Find the total sum of all root-to-leaf numbers.</p>

<p><strong>Note:</strong>&nbsp;A leaf is a node with no children.</p>

<p><strong>Example:</strong></p>

<pre>
<strong>Input:</strong> [1,2,3]
    1
   / \
  2   3
<strong>Output:</strong> 25
<strong>Explanation:</strong>
The root-to-leaf path <code>1-&gt;2</code> represents the number <code>12</code>.
The root-to-leaf path <code>1-&gt;3</code> represents the number <code>13</code>.
Therefore, sum = 12 + 13 = <code>25</code>.</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> [4,9,0,5,1]
    4
   / \
  9   0
&nbsp;/ \
5   1
<strong>Output:</strong> 1026
<strong>Explanation:</strong>
The root-to-leaf path <code>4-&gt;9-&gt;5</code> represents the number 495.
The root-to-leaf path <code>4-&gt;9-&gt;1</code> represents the number 491.
The root-to-leaf path <code>4-&gt;0</code> represents the number 40.
Therefore, sum = 495 + 491 + 40 = <code>1026</code>.</pre>