Here are some problem selections, which we think are good training material for programming contests.
- our tryalgo selection
- Methods to solve, annotated problems by category by Steven Halim (Singapore)
- algo.is, nice problems from Bjarki Ágúst Guðmundsson (NWERC course in Reykjavik University, Iceland)
- cses, problem set mainly from Antti Laaksonen (Finland)
- trains/paris, nice problems from Vitaly Aksenov (SWERC course in Télécom Paris)