Not a bad intro and appreciate the intention on keeping it short and simple, but personally for me I think Grokking Algorithms has the best beginner explanation

Not a bad intro and appreciate the intention on keeping it short and simple, but personally for me I think Grokking Algorithms has the best beginner explanations of Big O and basic algorithms / data structures. If I had to share resources with a learner, I'd suggest Grokking as an item to go deeper on after reading this article.