SPOJ
Solve problems from a huge judge archive in 40+ languages
SPOJ, the Sphere Online Judge, is a very large archive of programming problems. You pick a problem, write a solution and submit it to be judged. Problems are grouped into sections such as classical, challenge, partial, tutorial and riddle. Challenge problems score how good your answer is, not just whether it is right.
Free · Browser · Intermediate
About SPOJ
It trains classic algorithm skills and suits students and contest players who want a lot of practice. Problems range from very easy to very hard.
The judge accepts more than 40 programming languages, including some unusual ones. It is run by the Polish company Sphere Research Labs. You may need to pass a short browser check before the site loads.
On Breakpoint since 23 Oct 2026.