A topcoder is a high-quality programmer or (especially if spelled "TopCoder") one who competes in online programming contests at topcoder.com. Alternatively, TopCoder is used to refer to the company of that name, which hosts the contest.
TopCoder has been hosting algorithm competitions since 2001. Each contest consists of four phases:
- Coding phase (75 minutes) - Coders write programs to solve three short problems using C++, Java, C#, or Visual Basic. Each problem set consists of an easy, medium, and hard question, the difficulty of which is reflected in each problem's point value.
- Intermission (5 minutes) - After the coding phase ends, there is a short break before the challenge phase begins. This time can be used to test submitted solutions and think of challenge cases.
- Challenge phase (15 minutes) - Coders can challenge the submitted problems of other participants in their room by constructing test cases in an attempt to generate erroneous output. The challenger receives points for a successful challenge, and loses points for an unsuccessful challenge.
- System test phase - Each problem that survives through the challenge phase is run on many diverse test cases. Coders are awarded points for problems that pass all test cases, based on the speed and difficulty of problems solved. At the end of the contest, ratings are updated to incorporate each participating coder's performance.
TopCoder used to give out money every week to coders who did well in the weekly competitions, or Single Round Matches (SRMs), in a business model that seemed paradoxically brilliant. SRMs are now sponsored by outside companies such as Google and Yahoo!, and prize money is not awarded except for twice a year to winners and finalists of the TopCoder Collegiate Challenge (TCC, which is in the spring) and the TopCoder Open (formerly the Invitational, which is in the fall).
The business plan behind topcoder.com is actually rather interesting. One goal is to be a sort of recruitment center where companies can come and find programmers who are proven to be highly skilled. Another aim is to be an outsourcing center: TopCoder also hosts design and development competitions in which coders can compete to solve real world problems that third parties have contracted for.
In order to encourage newcomers in the early days (who would have little hope of beating out the best coders for prizemoney) to stick around and compete, the Iron Man system was set up under which coders were grouped into rooms of ten according to skill level (determined by rating). After the contest, the top (3?) (highest scoring) coders in each room were paid according to the skill level of the room (winners in the room of contestants with the top 10 ratings were paid more than those in the room with coders 11-20, and so on). This created some paradoxical situations such as the possibility of coming fourth in the whole contest and getting no money, while the 111th placed contestant got paid, and gave rise to ratings diving. Ratings diving, or taking a ratings dive was accomplished simply by doing very poorly on purpose in a particular contest (by opening and not submitting any problems or submitting incorrect challenges). As a result, a contestant would, in their next contest, be placed in a room with 9 coders among whom they had a good chance of winning some money. The idea was that the dramatically increased chance of winning money made up for the fact that the money to be won was a lesser amount given the lower average rating of the room.
Since, coders have been divided into two divisions (appropriately named Division I and Division II), and are grouped in rooms of up to 20 in such a way that within each division, the average coder ratings in each of the rooms are roughly equal.