Welcome. These are all the interview questions I have personally come across and/or found particularly helpful for myself for studying(unaffiliated with my previous or current employer(s)).
If you're here, you're either future Derek or one of my friends who is currently on the job search.
I recommend taking a look at categories that you may have trouble solving. Part of becoming better at these things just involves practice and pattern recognition. I've tried to summarize my thought process to reach the provided solution to each problem in a manner that is as succinct as possible. I'd recommend trying to remember the key points of that thinking as opposed to the actual solution :P.
You are more than welcome to update or add to anything if desired, but please do so in the form of a PR.