Since I have not coded consistently in quite a while I wanted a refresher course on data structures and algorithms and I found a good free textbook on the subject. The book uses pseudocode and explains each topic quite well. This is an introductory textbook so it isn't all that math-heavy but it does explain the Big O notation and how it relates to relevant topics. I would definitely rate it a 4 out of 5 stars for an intro course. Here is the link if you are interested. It is free and in PDF format.
https://open.umn.edu/opentextbooks/textbooks/171.
