"CodeForces: Codeforces.
It’s the best because:
- It creates many contests every week (up to 2 per week, sometimes 3 also).
- It has a very good helpful community.
- Most of the problems and the contests have very good tutorials which will teach you new things.
- It has always something to add, somethings new every year or half.
- It has a very good interface easy to use.
- It sponsors many contests which have prizes like money t-shirts or Xboxs.
- It supports many programing languages and different compilers more than any other website.
- It has a good search by topics:
- It has the ability to disappear the problems tags, which is a very good step to do while solving offline problems, check this.
- It has the option to sort problems by the most solved, which is a very good training method.
- It has a blogging section, section in which you can add a blog to ask for help in competitive programming or to suggest any idea, also you will find a lot of interesting things which people share.
- After participating in good amount of contests, you will be able to set a contest yourself, and take amount of money for doing that:
For contest writers: proposal tracking system - Codeforces - ACM-ICPC itself consider it as an identification of ICPC competitors this year
in this video ( the ICPC closing and awarding): [CF: codeforces, TC: topcoder].
- The website creator himself is a very good friendly person who don’t mind receiving messages asking/discussing things."
