I am from a non computer science background. I knew Leetcode long time ago, and have practiced about 80ish easy (and some medium) level problems, but never truly into it. Before Feb 2018, I failed a lot of interviews, like Amazon, Bloomberg, Goldman Sachs. Last March, I decided to focus more on Leetcode to practice my coding skill, so I purchased the premium, and everything started. I finally solved ~500 problems, and it was not an easy process at all. I basically sacrifised almost all my leisure time practicing on Leetcode.
After that it was pretty much July. I was contacted by several companies, so I decided to give it a shot, and I have to say, it feels totally different now. Coding interview was never so easy for me. I got several offers, including Apple Linkedin Google Uber.
If you are like my background and have a dream to go to one of the best tech companies in the world, you first need to have a heart to work very hard, and you also need a tool like Leetcode to help you get there.