Resources

Judges with Regular Contests

• Codeforces: The most popular judge, with frequent contests and thousands of high quality problems of various difficulty levels. (codeforces.com)
• AtCoder: Another popular judge, particularly popular for its frequent beginner friendly “AtCoder Beginner Contests.” (atcoder.jp)
• CodeChef: Another online judge, contests are held every wednesday. (codechef.com)

Problem Sets

• BdOI Past Problems: Problem statements from past editions of BdOI. (olympiad.org.bd/resource)
• CSES: Judge with 300+ highly educative problems. (cses.fi)
• oj.uz: Online judge with past problems of many OI contests. (oj.uz)

Learning Resources: Books

• Competitive Programmer’s Handbook by Antti Laaksonen (cses.fi/book/book.pdf)
• Competitive Programming 3 by Steven Halim

Learning Resources: Websites

• USACO Guide: Website with tutorials on various algorithms used in OI contests sorted by difficulty, along with practice problems and their solutions. (usaco.guide)
• CP Algorithms: Wikipedia of CP algorithms and tricks. (cp-algorithms.com).
• Codeforces Catalog: List of the most useful blogs on Codeforces. (codeforces.com/catalog)
• Shafaet’s Blog: Bangla blog covering various topics of competitive programming. (www.shafaetsplanet.com/planetcoding)

Learning Resources: Videos

• Codeforces Edu (codeforces.com/edu/courses)
• Errichto (youtube.com/c/Errichto)
• Errichto 2 (youtube.com/c/Errichto2)
• Algorithms live (youtube.com/c/AlgorithmsLive)

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Communities

• CJC: Discord server of BdOI enthusiasts. (discord.gg/8N47hNPhh9).
• Bangladesh CP Server: Discord server of all types of CP enthusiasts from Bangladesh. (discord.gg/RmmKvjMZwT)

Miscellaneous

• OI Checklist: Checklist to track the OI problems you’ve tried and solved. (oichecklist.pythonanywhere.com).
• CLIST: List of upcoming CP contests, along with many more features. (clist.by).
• Awesome Competitive Programming: List of various awesome things related to CP. (github.com/lnishan/awesome-competitive-programming)

The End