USA Computing Olympiad (USACO) Online Contests

Difficulty varies by division from Intermediate to Expert, A free series of timed online algorithmic programming contests with Bronze, Silver, Gold and Platinum divisions. Online contests welcome participants worldwide. New contestants begin in Bronze, while U.S. pre-college rules apply to training-camp and international-team selection. The main challenge is turning algorithmic ideas into correct, efficient programs under contest conditions; higher divisions require promotion and deeper techniques.