Which leangue should I do to do robotic enginiering?
That is a hard question in this pandemic era, as they are probably all but shut down. I can highly recommend FIRST Robotics Challenge (FRC). I am not familiar with others. If you can find any leagues that are still active in your community then have a talk with the leaders and see if it is a good fit. By any means possible, it is worth joining to get experience and scholarships.
Decimal to Hex in C++