If I can suggest something - don't neglect physical training. You will need a lot of endurance (both physical and mental) to go through some of those onsite interviews. Also take breaks if possible.
As to resources - as many have said earlier - leetcode.com this is basically the place to go for problems to practice and there is also really great community. When practicing problems and analyzing answers in the beginning you will find what kind of topics are important and from there you can find more details in the textbooks (it's worth doing that). There is some good content also on Youtube but not all of it is good (despite high number of views and positive comments).
> You will need a lot of endurance (both physical and mental) to go through some of those onsite interviews.
I have gone through some interviews where it is really grueling and mentally taxing. What do you suggest to improve endurance especially mental. It becomes very hard to concentrate on coding after almost 4 hours of interviews.
As to resources - as many have said earlier - leetcode.com this is basically the place to go for problems to practice and there is also really great community. When practicing problems and analyzing answers in the beginning you will find what kind of topics are important and from there you can find more details in the textbooks (it's worth doing that). There is some good content also on Youtube but not all of it is good (despite high number of views and positive comments).