Tip 1 : I practiced a lot of problems related to Data structures on the Coding ninjas platform and other coding platforms.
Tip 2 : If you are stuck somewhere in a problem and want to see reference, first, try to understand the algorithm and then move on to code.
Tip 3 : Just see the algorithm that is how to approach first and don't try to understand from the code right off the bat, code has finer implementation variation that can be done on your own if you are clear with the algorithm. Also for big product companies, prepare enough problems of graphs and trees as these are the most important topics for interviews.