What is the best for Dijkstra's algorithm: set with erasing of the vertices adjacent to the current one and the subsequent insertion of them with the new values or a priority_queue with a lot of irrelevant vertices? Or maybe some other approach using std?

Why can I check tests in the Contests, but cannot do this in the Gym? I find it rather strange. And are the tests used in the Gym different from the tests in the Contests? I am trying to solve a problem from one of the contests, and while my program passes the tests from the Contests, it can't get "Accepted" in the Gym.