For problem 710B following solutions:

1. AC solution using collections.sort.
2. TLE solution using Arrays.sort.

Does this mean Arrays.sort is slow, and should not be used in contests ? Anybody encountered such problem before ?

http://codeforces.com/contest/721/problem/E

Couldn't understand the solution even after reading the editorial. Someone please help.

UPD: In hope that somebody might explain the solution :)