agree with you, great problem set. Although I only tried 2 problems, I found both of them accessible, but not straightforwards. It was as I imagined it would be, but this time was very hard to pass to next round. Anyway, congrats to all the advancers!!!!(specially to wleite, only sudamerican at finals)
There's got to be more to nemesis_nitt's amazing performances - it's not like he'd only done one match before the TCO, he's been consistently grey/green - in fact his pre-TCO graph looks a bit like mine! Maybe he's spent months doing nothing but train for this? Anyway, TC definitely need to do an interview with him as I'm sure I'm not the only one who want's to know "how do I go from Div2 to the TCO finals".
Examining his solutions, it appears that sometime after the quals he suddenly understood how to encapulate things in functions, write quick short memoized/dp solutions, and reduce the number of lines in his program by half. These are kind of discrete things, so it's at least moderately plausible to me that he just really stepped up the training effort. It is strange though.
Well, he has consistently showed, in his first 20 matches, that he finds trouble even solving simple Div 2 500 problems. Do you actually think one could go from such a consistently bad performance in trivial problems to placing 2nd in TCO R4 in under a month?