144. Binary Tree Preorder Traversal

Dec. 2, 2018

Introduction

It is time for me to work on medium level tree algorithms. I only have 8 unlocked medium level tree algorithms to work on. After I worked on one tough medium level tree over one hour, this one is considerably so easy for me to write, I did in less than 30 minutes.

My practice

I spent over 20 minutes to write the solution, I felt not stress at all. Here is my discuss link.