Sites and apps similar to AtCoder include LeetCode, which has a free version. Other options are HackerRank, Codewars, Topcoder and Codeforces. In total there are eight Code Learning Services like AtCoder for self-hosting.
LeetCode is a platform for learning and improving coding skills with the goal of being fully prepared for programming interviews. Choose problems to solve from categories such as System Design, Algorithms and Database, join code contests and engage in mock interviews.
United States
A fun social platform for hackers to solve interesting puzzles, build quick hacks, code game bots and collaborate to solve real-world challenges.
United States
United States
Topcoder provides members opportunities to demonstrate their expertise, improve their skills, and win cash, while helping real world organizations solve real world problems.
Codeforces is a website that hosts competitive programming contests.
CodeChef is a not-for-profit educational initiative by Directi, an Indian software company. It is a global programming community that fosters learning and friendly competition, built on top of the world’s largest competitive programming platform.
India
Sphere Online Judge created for the coders' community to train, to learn and to make progress. With thousands of programming problems and an international group of users Spoj is one of the best programmers' communities and online judges in the world.
Russia
Poland
EU
