Here's how to get the most from this material.
Active learning. Don't just read solutions. Solve problems first. Time yourself at minutes. Explain your thinking out loud.
Spaced repetition. Review problems after day, week, month. If you can't solve it quickly the second time, you haven't learned the pattern.
Mock interviews. Practice with a friend or a platform like Pramp. Explaining your thought process matters as much as getting the answer right.