I started with LeetCode just out of curiosity. Very frustrating at the beginning the test cases got me easily. And I started with C, there is no STL comes with it.

After I switched to C++, things become a bit reasonable. I did questions per topic. There is no interview planned so I took my time. I was taught all these areas in school so eventually I took out the old text book that speeds things up quite a bit.

The coding interviews are surprising easy for me. There is no exact the same questions but a mixture of basic ideas and of course reflecting your practice efforts. Online assessment are graded by machine that's more important for practice, practice

In summery, here is my takes on this

1. get the basic ideas right from the textbook first
2. practice and learn the lessons. taking your time to build confidence

Good luck and enjoy the process.