And there it is. You can access at : http://apps.topcoder.com/wiki/display/tc/SRM+570
Feel free to comment, even though I'll be disconnected for the weekend.
Div1 easy / div2 medium were a bit too fun to explain. Like I mentioned I was in a rush when making this editorial, but those problems are just too good to leave it incomplete not mentioning at least four approaches. A good div 1 easy / div 2 medium has tons of approaches, so that fools (e.g: me) have more of a chance to fail challenges or to succeed.
Div2 easy seemed a bit heavier than usual. My initial solution seemed a bit too complicated to explain. So I went shopping the division 2 summary looking for what kind of solution were the people in that division using. It seems that sorting as a shortcut was too esoteric for that level.