I discovered https://app.codility.com/programmers/lessons/ in 2016. I heard about TopTal (http://toptal.com) then and about their hiring process where they used some codility tasks. I did several lessons and abandoned that. But all the time I was thinking that the tasks were great for a technical sreening process.
Here I'm collecting my solutions of the tasks. As you can see I found solutions not for all tasks and I share a link in a case it's so.