How does HackerEarth work?

You need to register at that site. It is completely free and no need to subscribe if you are preparing for interviews and practicing and learning coding. Multiple programming languages are supported here. Some coding problems are very difficult to solve, so your skills will be improved definitely. Almost every company's hiring challenges are there almost every week. You need to create a profile and submit resume and apply for job hiring challenges and take part in that. Monthly coding challenges are also there.