Sphere Online Judge

Sphere Online Judge (SPOJ)
The Sphere Online Judge Problemset SPOJ is a programming site with a collection of selected but wide range of problems. It contains problems of all difficulties covering standard and non-standard algorithms. Moreover its problem set is increasing as one could post his/her own homemade problem. It also covers all the problems of the prestigious ACM International Collegiate Programming Contests(ICPC).

About
The SPOJ Project is developed and maintained by Sphere Research Labs, based in Gdynia, Poland .