I know that feeling of the problems seeming impossibly hard all too well - it was the same at the Physics Olympiad, which was pushed pretty hard by one of the p

I know that feeling of the problems seeming impossibly hard all too well - it was the same at the Physics Olympiad, which was pushed pretty hard by one of the physics teachers at my high school (in Austria), who also happened to be one of the organisers of the state and national events. It helps to know that the problems are intended to be so hard that nobody gets full marks. I didn't realise this early on, but it's of course obvious in hindsight - you wouldn't want a draw, you want a nice, clean exponential distribution of scores. (unlike an exam, where a gaussian distribution is usually what you're after) It sounds as if the IOI organisers (or at least the Danish organisers) provide possible solutions/approaches for the problems. This is great, it always pissed me off no end at the Physics Olympiad that everything was all hush hush and you had to try and find someone to explain the problems you failed miserably on as we never got to see the correct answers (let alone a breakdown of our scores by problem). I think the national format varies from country to country, but in case it's of interest: In our case, the Physics and, as far as I know, Maths & Chemistry Olympiads were split into school, state, and 2 stages of national competitions. I think each school sent up to 4 people (selection up to the school) to the state competition, which was standardised across the country and was half a day. The best 3(?) from each state, plus a selection of those with high scores then made it to the first round of the federal competition, which I think was a whole-day "exam". The best 15 or so from that then went for a 2-week intensive course held in different cities each year, with 4 different physics teachers teaching you new physics all day. It culminated in a 2-day competition, from which the top 5 got to go on yet another 1-week intensive course and the international competition. (much to my surprise, I ended up qualifying for the IPhO 3 times, in 2000, 2001 and 2002 but only ended up participating once in 2001 [Antalya, Turkey] - for these events it helps to live in a country with a small population I guess) I kind of wish I'd been sufficiently driven to self-study for the Informatics Olympiad at the time. (CS was nonexistant at my school; I'd only vaguely heard of the IOI, whereas Physics, Chemistry and Maths were encouraged - I probably tried the maths one too young, I was sufficiently intimidated not to try it again; the physics teacher was a lot more welcoming and better at keeping all ages making progress) I bet I'd be a better programmer for it now, and I had all the time in the world back then. In any case: good luck Simon!