<p>Codeforces is the most active competitive programming platform in the world, running weekly rated online contests across multiple difficulty divisions. Each round presents 5–9 algorithmic problems to be solved within 2–3 hours, with a global rating system and colored-name tiers recognising top performers.</p> <ul> <li>Open to all ages globally; free account required; Singapore students participate fully</li> <li>Multiple rated rounds per week: Div. 1, Div. 2, Div. 3, Div. 4, Educational, and Global rounds</li> <li>Rating-based divisions: Div. 4 (rating under 1400), Div. 3 (under 1600), Div. 2 (under 2100), Div. 1 (1900+)</li> <li>Div. 4 and Div. 3 are the recommended entry points for beginners</li> <li>NUS CS3233 Competitive Programming uses a Codeforces maximum rating of at least 1400 as a pre-acceptance indicator</li> <li>Free to participate; rating and leaderboard are the primary outcomes – most rounds have no cash prize</li> </ul> <p>Register a free account and join any upcoming round from the Codeforces contests page.</p>