Codeforces

Codeforces is a website that hosts competitive programming contests. It is maintained by a group of competitive programmers from ITMO University led by Mikhail Mirzayanov. Since 2013, Codeforces claims to surpass Topcoder in terms of active contestants. As of 2018, it has over 600,000 registered users. Codeforces along with other similar websites are used by top sport programmers like Gennady Korotkevich, Petr Mitrichev and Makoto Soejima, but also non-celebrity programmers interested in furthering their careers.

In Codeforces app, you can,
★ Get the list of all the contests
★ Get the list of all the problems in the problems set
★ Search and get details of any user using its codechef handle
★ Enable dark mode in Settings