Good online judge systems / contest platforms to practice.
| ☆ | Name | Description |
|---|---|---|
| ★★★ | Codeforces | Codeforces is one of, if not, the most popular contest platforms out there. Currently maintained by Saratov State University, it features regular contests and countless awesome original problems. Additionally, every contest provides immediate helpful tutorials (usually) written by the authors themselves. Codeforces also houses a strong and engaging community. All in all, one would indeed learn and improve tremendously here. |
| ★★★ | Topcoder | Topcoder has been around since 2001. Rich in history, It's considered to be one of the most prestigious organizations when it comes to technology competitions. Hundreds of SRMs gave birth to an abundant problemset. Problems here are typically more challenging than others and Topcoder therefore appeals to many elite programmers. The annual Topcoder Open (TCO) is also a widely-discussed event. |
| ★★★ | Google Code Jam | Google Code Jam is certainly one of the most highly-esteemed programming competitions. The competition consists of unique programming challenges which must be solved in a fixed amount of time. Competitors may use any programming language and development environment to obtain their solutions. |
| ★★★ | AtCoder | AtCoder is a new but phenomenal contest platform created by a team of highly-rated Japanese competitive programmers. |
| ★★☆ | CodeChef | CodeChef is a non-profit educational initiative of Directi. It's a global competitive programming platform and has a large community of programmers that helps students and professionals test and improve their coding skills. Its objective is to provide a platform for practice, competition and improvement for both students and professional software developers. Apart from this, it aims to reach out to students while they are young and inculcate a culture of programming in India. |
| ★★★ | SPOJ | The SPOJ platform is centered around an online judge system. It holds a staggering amount of problems prepared by its community of problem setters or taken from previous programming contests, some of which are great problems for practice (refer to the Problem classifiers section). SPOJ also allows advanced users to organize contests under their own rules. |
| ★★☆ | Timus | Timus Online Judge is the largest Russian archive of programming problems with automatic judging system. Problems are mostly collected from contests held at the Ural Federal University, Ural Championships, Ural ACM ICPC Subregional Contests, and Petrozavodsk Training Camps. |
| ★☆☆ | HDU | HDU is an online judge maintained by Hangzhou Dianzi University. It's home to many classic problems from the Chinese IOI scene. |
| ★★☆ | Aizu Online Judge | Aizu online judge is a contest platform and problem archive hosted by The University of Aizu. It has a lot of great problems from programming competitions in Japan. |
| ★★☆ | UVa | An old-school problem archive / online judge with rich history. Thousands of problems, including many classic ones, are featured here. However, it is strongly advised that you practice with uHunt following its "Competitive Programming Exercise" section. |
| ★★☆ | HackerRank | HackerRank is a company that focuses on competitive programming challenges for both consumers and businesses. HackerRank's programming challenges can be solved in a variety of programming languages and span multiple computer science domains. |
| ★★☆ | POJ | POJ is an online judge with many great problems maintained by Peking University. Most Chinese competitive programmers began their journey here. The platform is really dated so mysterious compilation and run-time issues may occur. |
| ★★☆ | Project Euler | Project Euler features a stunning set of good math problems. It also hosts a forum where people can discuss. |
| ★☆☆ | Hackerearth | HackerEarth is a startup technology company based in Bangalore, India that provides recruitment solutions. |
| ★☆☆ | Caribbean Online Judge | COJ is hosted by University of Informatics Sciences (UCI, by its acronym in Spanish), located in Cuba. Feature ACM ICPC and Progresive constest styles, mostly from Caribbean and Latin American problem setters, also has problem classifier and contest calendar. |
| ★★☆ | CS Academy | New in the competitive programming scene, CS Academy is a growing online judge that hosts competitions once every two weeks. It supports live chat, interactive lessons and an integrated online editor (that actually works). |
| ★★☆ | Russian Code Cup | Programming competitions powered by Mail.Ru Group. Competition consists of 3 qualification, 1 elimination and 1 final rounds. For each round contestants are given 4-8 problems which must be solved in a fixed amount of time. |
| ★★☆ | CodeFights | CodeFights is a website for competitive programming practice and interview preparation. It features daily challenges of varying difficulty, an archive of problems and regular (every 15 minutes) mini-tournaments. Good for beginners. |