Watched second video and took detailed notes

Author: csirick2020

README.md

@@ -578,7 +578,7 @@ But don't forget to do coding problems from above while you learn!
 - Don't worry if you don't understand all the math behind it.
 - You just need to understand how to express the complexity of an algorithm in terms of Big-O.
 - [X] [Harvard CS50 - Asymptotic Notation (video)](https://www.youtube.com/watch?v=iOq5kSKqeR4)
-- [ ] [Big O Notations (general quick tutorial) (video)](https://www.youtube.com/watch?v=V6mKVRU1evU)
+- [X] [Big O Notations (general quick tutorial) (video)](https://www.youtube.com/watch?v=V6mKVRU1evU)
 - [ ] [Big O Notation (and Omega and Theta) - best mathematical explanation (video)](https://www.youtube.com/watch?v=ei-A_wy5Yxw&index=2&list=PL1BaGV1cIH4UhkL8a9bJGG356covJ76qN)
 - [ ] [Skiena (video)](https://www.youtube.com/watch?v=z1mkCe3kVUA)
 - [ ] [UC Berkeley Big O (video)](https://archive.org/details/ucberkeley_webcast_VIS4YDpuP98)