Given a binary tree, return the preorder traversal of its nodes' values.
Example:
Input:[1,null,2,3]1 \ 2 / 3 Output:[1,2,3]
Follow up: Recursive solution is trivial, could you do it iteratively?
Given a binary tree, return the preorder traversal of its nodes' values.
Example:
Input:[1,null,2,3]1 \ 2 / 3 Output:[1,2,3]
Follow up: Recursive solution is trivial, could you do it iteratively?