Hi, I'm now crazing with memset() and fill() or fill_n(), in the Problem D Div3 Round #636, i used fill_n() and it was TLE, so I changed to memset() and accepted. I dont't understand the way memset work. Can you explain me ? Thank you

*In addition, sometimes i use memset but it doesn't work well Here are my submissions: TLE: https://codeforces.com/contest/1343/submission/77570494 Accepted: https://codeforces.com/contest/1343/submission/77570825