Incoming links: Unlicense
Project Euler Created 2025-03-20 Updated 2025-12-25
They don't have an actual online judge system, all problems simply have an integer or floating point solution and they just check that you've found the value.
The only metric that matters is who solved the problem first after publication, e.g.: projecteuler.net/fastest=454. The "language" in which problems were solved is just whatever the user put in their profile, they can't actually confirm that.
Project Euler problems typically involve finding or proving and then using a lemma that makes computation of the solution feasible without brute force. As such, they live in the intersection of mathematics and computer science.
Repositories of numerical solutions:
Repositories of code solutions:Basically no one ever had the patience to solve them all. What we need is a collaborative solution.
- euler.stephan-brumme.com/ large number of solutions in C++, stopped around 600. Informal permissive license, e.g. at: euler.stephan-brumme.com/243/Asked for a more formal open license at: github.com/stbrumme/euler/issues/7All of my solutions can be used for any purpose and I am in no way liable for any damages caused.
- www.ivl-projecteuler.com/home 330+ solutions in Python as of 2025. Random looking problem selection. On GitHub: github.com/igorvanloo/Project-Euler-Explained under Unlicense license, a public domain license.
- www.nayuki.io/page/project-euler-solutions. Large number of solutions, mostly in Java and Python primarily but also Mathematica and Haskell sometimes. Proprietary license.
Problems are under CC BY-NC-SA: projecteuler.net/copyright
Once you solve a problem, you can then access its "private" forum thread: projecteuler.net/thread=950 and people will post a bunch of code solutions in there.
How problems are chosen:
projecteuler.net says it started as a subsection in mathschallenge.net, and in 2006 moved to its own domain. WhoisXMLAPI WHOIS history says it was registered by domainmonster.com but details are anonymous. TODO: sample problem on mathschallenge.net on Wayback Machine? Likely wouldn't reveal much anyways though as there is no attribution to problem authors on that site.
www.hackerrank.com/contests/projecteuler/challenges holds challenges with an actual judge and sometimes multiple test cases so just printing the final solution number is not enough.