I don’t quite understand why this method works (should give AC) and how to calculate the time complexity for it.
Also, I do not understand what are the datastructures that are defined in the solution, and why wasn’t a normal unordered_set used? I tried to use that and got a TLE for the second last test case instead of the last (last one got AC!).
Can anyone explain how to use those pbds data structures? I only know the basic ordered_set for order statistics. what are the other ones?
Edit: the problem was with the hash. using neal’s custom hash solves it! Here is the AC solution: https://cses.fi/paste/d67707c48bbca93b2b85e1/