Online judge beginner
AtCoder
Its Beginner (ABC) contests are the best way in: short, well-written problems with a gentle difficulty curve.
Open resourceResources
Material selected for training competitive programming, organised by type and by level. You do not need to use all of it: pick one judge and one book, and be consistent.
Starting from scratch?
The shortest, best-tested route: read Competitive Programmer's Handbook while you work through the CSES Problem Set from beginning to end. Once the problems start coming out effortlessly, join AtCoder's ABC contests to train against the clock.
5 of the 12 resources on this page are marked as suitable for beginners.
Online judges
Platforms to practise and compete on. Start with one and stay there until it feels comfortable: switching judge every week does not help.
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- Online judge beginner In Spanish
omegaUp
A Latin American platform with problem statements in Spanish and guided courses. Highly recommended if you are just starting out.
Open resource - Online judge intermediate
Codeforces
The most active online judge on the competitive circuit. Weekly contests, a huge problem archive with editorials, and a rating system that helps you measure progress.
Open resource - Online judge intermediate
Kattis
The judge officially used in many ICPC regionals. Its interface and input/output formats closely match the real contest.
Open resource - Online judge intermediate
Virtual Judge
Lets you assemble private contests combining problems from several judges. Ideal for simulating a full regional with your team.
Open resource
Problem archives
Collections organised by topic or by edition. Ideal for drilling one specific topic or simulating a real contest.
- Problem archive beginner
CSES Problem Set
Three hundred problems ordered by topic. Working through them end to end covers almost the whole basic competitive programming syllabus.
Open resource - Problem archive advanced
Archivo oficial de problemas ICPC
Problem statements from every World Finals edition. The best material for calibrating the level you are aiming at.
Open resource
Books
The theory behind it all. They pay off far more when read alongside solving problems, not before.
- Book beginner
Competitive Programmer's Handbook
Antti Laaksonen's free book. The standard reference for moving from knowing how to program to competing. Reads well alongside the CSES Problem Set.
Open resource - Book advanced
Introduction to Algorithms (CLRS)
The academic background reference. Useful for rigorously understanding the algorithms that competitors use from memory.
Open resource
Guides and references
Quick-reference material for training sessions, and a good base for putting together the team's printed notebook.
- Guide beginner
USACO Guide
A tiered learning path, from bronze to platinum, with problems selected for each topic. Excellent for structuring training.
Open resource - Guide intermediate
CP-Algorithms
An encyclopedia of algorithms and data structures with ready-to-use implementations and clear explanations of complexity.
Open resource
Video
Commented solutions. Useful for seeing how someone experienced reasons through a problem from scratch.
- Video intermediate
Errichto — Algorithms
Live solves and explanations of contest techniques by a World Finalist. Very good for learning how to reason through a problem.
Open resource
Something missing?
This list is maintained by the community. If you know of a resource that should be here — especially material in Spanish — tell us and we will review it.