There's always Leetcode and Hacker Rank. If you get involved in an open source project your horizons may narrow quickly, so it's best understanding the strength

There's always Leetcode and Hacker Rank. If you get involved in an open source project your horizons may narrow quickly, so it's best understanding the strengths of being a generalist or being best in a particular area. The key thing in the development sphere is that nothing stands still, and neither should you.