Hi, is there a reason why my submission* got accepted meanwhile my rough estimate for time complexity is O(n^3), because i did a dfs and for every node i calculate a subset sum of each subtree size. Or is this because of weak tc? thanks

*) https://codeforces.me/contest/1856/submission/290385616

While we are in an ICPC contest, can we use earbuds to handle noises that other teams make during the contest? Or is anyone here have a suggestion to handle this similar thing?

Can anyone give me advice on how to learn CP quickly? I have read several catalogs that talk about this, but I want to know, is there anything you wish you knew earlier?