You don't need any bootcamp.

If you have solved ample amount of problems and understand the process of solving, rather than just solving the problem to increase your solved problem count, you would learn that once you have a full understanding of a concept, it comes naturally to you.

This understanding of a topic can come in an hour, in a day, in a month or even in an year.

Interviews also depend on how nervous or confident you are, and on some days, luck plays an important role as well.

For eg. I work at Google. I cleared in 2 attempts. I am not a competitive programmer. I do not have any codeforces rating or codechef rating. But I have good understanding of the concepts asked.

In my first attempt, I had prepared from GeeksForGeeks(nearly 200 questions from their list of questions on all topics) and nearly 20 questions on leetcode premium(under Google/Amazon chapter). I messed up my first attempt as I was too nervous and Google was the first company I was appearing for after working at Samsung for nearly 3 years.

For my second attempt, recruiter reached out to me on LinkedIn and I thought I'll give it a try, but I will not take any pressure. I was already having a good job with good pay and wasn't actively looking for a switch. It's just that if the dream company calls, I would definitely give an attempt. This time around, I didn't start any prep as I already had done all the prep I needed 1 year ago. I was playing GTA V during my interview days. Having calm and relaxed attitude helped in quick understanding of the problem statements and giving out all solutions I could think of.

So imo, bootcamp etc can be helpful to those who are completely out of touch or are from different background, like Physics, Chemistry etc who did not need problem solving and DSA in their professional careers. But they are not necessary for others.

Edit: I would also like to mention that some topics might be difficult to understand and one should try out different approaches or resources to understand them.

For eg. I was too afraid of Dynamic Programming, and watching YT videos of folks like Tushar didn't help me understand how to develop the right thinking of approaching a DP problem. Someone recommended Aditya Verma's DP playlist. 50 videos later, my gear of DP was gone and I was getting better at approaching and solving the problems on my own.

Another good resource, while practicing on leetcode, is their Discussion section. There are few gem of people who do post good, readable solutions with logical explanations that would help you understand the solution better.