CodingBat vs DMOJ

CodingBat is a free browser-based site for practicing Java and Python through live coding problems. Users enter code in a text area and click Go to save, compile, run it, and see the result immediately; nothing needs to be installed. Problems in each section become harder toward the end, and some include hints or solution code. Every Warmup section has solution code available. The exercises are intended for homework, self-study, labs, and live lecture examples. An account saves code and completion checkmarks, lists completed problems, and provides progress graphs and code badges. Accounts can share information with a teacher account, whose report lists students and their completed-problem counts. Without an account, work is forgotten after a session ends following two hours without activity. Users can also create custom pages and author Java or Python problems. CodingBat says cookies maintain login sessions and that it does not use third-party cookies. It collects regular web-server logs and may use submitted code and data for teaching-technology research.

DMOJ is an open-source platform for programming contests and an archive of programming problems. Its archive includes tasks from past CCC, CCO, COCI, IOI and JOI competitions, among other sources, and it runs a monthly open programming competition. Public contests can be hosted at no cost. Contest formats include ICPC, IOI, AtCoder and ECOO, with system testing, hidden scoreboards and virtual participation. Judging supports interactive and signature-graded tasks, runtime data generators, custom output validators, per-language resource limits and scaling to hundreds of judging servers. Problem statements can include Markdown, LaTeX math and figures, syntax highlighting, PDF generation and built-in editorials. DMOJ integrates with Stanford MOSS for plagiarism checking and supports OAuth login, two-factor authentication and fine-grained staff permissions. Documentation is available for self-hosting the site and judge; the installation guide says the site is tested with MySQL and is unlikely to work with other databases. AI use is prohibited in rated contests, and judging resources cannot be used for AI training.