# Problem Definition

## Description

Given a binary tree, return the pre-order traversal of its nodes’ values.

Example: Given binary tree

```plaintext
   1
    \
     2
    /
   3
```

return [1,2,3].

Using recursion is not allowed.

## Notes

1. [YT - Vivekanand Khyade - Binary Tree Traversal](https://www.youtube.com/watch?v=98AGQU0z2wg)
1. [YT - Tushar Roy - Iterative Pre-order Traversal of Binary Tree](https://www.youtube.com/watch?v=elQcrJrfObg)
1. [GitHub - Tushar Roy](https://github.com/mission-peace/interview/blob/master/src/com/interview/tree/TreeTraversals.java#L64)