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I couldn't understand the meaning of the following code which is part of a program...It will be very helpful if anyone clarify this...Thank you all!!
#ifdef ONPC
mt19937 rnd(228);
#else
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif
It is initializing a random number generator. If it's on the author's personal computer (
#ifdef ONPC), then he initializes it with a set seed (228), so it is easier to debug, because it provides the exact same numbers every time. If it is on the Codeforces judge system (#else), then he initializes it with a basically unpredictable number based on the system time, which prevents people in his room from hacking him (by submitting a test case on which the random number generator degrades to worst-case performance).