

International Olympiad in Informatics Problems - dangoldin
http://www.ioinformatics.org/history.shtml

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Also worth checking out is USACO. The USACO training gate allows you to start
with easy problems and the build up to the point where you can do the ioi
problems. Finish the entire thing and I can guarantee that you will at least
have a good understanding of the ioi problems.
<http://ace.delos.com/usacogate>

