Highly recommended for those looking to grasp discrete math at a deeper level: http://www3.cs.stonybrook.edu/~algorith/math-video/
Skiena goes through the amazing Concrete Mathematics book (which he didn't write). Warning - it is from the time when people used markers to write out their lecture notes!
The conclusion of Professor Skiena's answer to a question about tech interviews[0]:
"When I had a startup company, all candidates we interviewed were amazed that I never asked them algorithm questions! I wasn't hiring them to answer puzzle questions, so why ask? And I am quite proud of the very good people we hired at General Sentiment".
[0] https://www.reddit.com/r/cscareerquestions/comments/7vxid2/i...