I attached all the resources which I found useful during my preparation.
Learn C++ and STL.
For STL: click here
Don't learn Data Structure or Algorithm now.
Go to Codeforces ProblemSet and solve questions according to rating.
Start with 800 rated problems, do 20-60 questions in each rating, and gradually increase the rating.
Solve till 1200 rating without learning any topic.
After that learn:
Note: After learning any topic, do topic-wise practice on leetcode. But in CF, do rating-wise practice, not topic-wise.
You can solve till 1400 rating only by above topics.
After 1400 learn these:
After 1600 learn these:
Codeforces has so many ad-hoc and constructive algo problems. To become good at them, practice is the only way. There is no particular resource or trick to solve those problems. Just do more and more practice to become good at them.