ok so i know it sounds like a really stupid question and that i should just upsolve and learn from my mistakes..

but how? how do i learn from absolutely idiotic mistakes from problems that i should have definitely been able to get through, and how do i stop this from happening in contests again?

also, how do i deal with problems that i have no idea on how to even approach? like for C, i've done a bunch of standard tree stuff on usaco, but i had no idea what to do after figuring out that an edge is useless if it doesn't cross the 1->n path, and how to calculate whether to keep the edge or not when it does.

honestly just a bit of a rant i'm kinda salty i gave up on B after a silly mistake and then proceeded to fail at C miserably for an hour...