Use of ext/pb_ds library in ACM ICPC?

Can we use this library in ACM ICPC contests mentioned in this
link: codeforces blog

This is generally used to create ordered tree. This structure supports same operations as set AFAIK, along with two new features find_by_order() and order_of_key().

include < ext/pb_ds/assoc_container.hpp > // Header file

using namespace __gnu_pbds;

//