Topcoder!

A fun social platform for hackers to solve interesting puzzles, build quick hacks, code game bots and collaborate to solve real-world challenges.

Duel with friends and foes in head-to-head programming battles!

Achieve code mastery through challenge.Improve your skills by training with others on real code challenges

SPOJ (Sphere Online Judge) is an online judge system with over 315,000 registered users and over 20000 problems. The solution to problems can be submitted in over 60 languages including C, C++, Java, Python, C#, Go, Haskell, Ocaml, and F#. SPOJ has a rapidly growing problem set/tasks available for practice 24 hours/day, including many original tasks prepared by the community of expert problem setters associated with the project.

Learn to code (for free) with interactive challenges. Gain XP, unlock achievements and climb the leaderboard. It's the fastest, easiest, most addictive way to learn.

Devskiller is an online testing platform that helps companies verify programming skills. It’s designed to directly address the key problems of hiring the IT talent: • Programming skills quality assessmentDevskiller helps to verify tech skills of programming languages, frameworks and libraries, imitating a real programming environment.• Customized online testingAssessing candidates at the first screening step results in a smaller, better-qualified and suited IT candidate pipeline before the time-consuming process of interviewing.• HR user-friendly toolDevskiller is easy to use for staff with no technical background, decreasing high costs of engaging the tech team.• EducationDevskiller helps also to evaluate the progress of education of programmers.In short, our customers use the platform to reduce the number of unnecessary interviews by 60-70% and to decrease the time-to-hire by 30-50%. »

The online programming practice in java and python.

CodeChef was created by Directi as a way to continuously challenge and engage the developer community. Our goals are to provide a platform for practice, competition and improvement as well as enable developers to benchmark their skills against their peers. We’re having fun with the site and hope you will too.

At Programmr you can code, compile & run your programs directly in the browser. Supported platforms include C++, Java, PHP, C#, Flex, J2EE, Objective-C and many others. Programr is the fastest way to become a programming guru!

At Geektastic we help our client's thoroughly evaluate their future talent using our unique peer reviewed code challenge platform. We believe a candidate is worth more than a score and the only way to thoroughly understand how suitable they are to work in your team is to have a human look over their code. The platform allows clients to license code challenges from our portfolio or upload their own, they can also choose to have our on-demand team (of exceptionally talent software engineers) carry out the thorough review or perform it in-house. »

Kattis helps companies make safer recruitments and attract the best developers with its dynamic challenge platform.