the same c++ code was accepted when I used visual studio, but gave TLE 8 with g++ 9 (or g++ 9, C11)

Same happened to me. I've removed everything from the code except scanf("%d", &t); and it took 1.9 seconds just to read test #8 input using G++. Same code runs in 0.25 seconds under Visual C++ 2010.

Thank you. I also scaned with scanf("%d", &t) and got ~1.5+/- sec using G++ and ~0.3 sec using VC++.
Another idea to optimize is to scan with gets() and hex values.

Edited by author 28.09.2016 00:02

Edited by author 28.09.2016 00:02

Using buffered i/o, G++ 4.9 C++11,  and  std::unoredered_set :
 http://acm.timus.ru/rating.aspx?space=1&num=1196 !!!