Since I can't post on AtCoder and admins of AtCoder are also on CodeForces, I post it here.

AtCoder holds ABCs, which is for beginners. What's the definition of beginners? Recently, there appears many problems with algorithms such as FFT / NTT, flows, SAM / SA etc in ABCs.

Are these really for beginners? Of course these algorithms are in ACL, but if participants really want to solve them, them must know the tricks in them like using FFT to do the string matching, the max flow equals to the min cut, the meanings of points & arcs on SAM. All of them are not really for beginners, at least I think so.

The purpose I do this post is that I hope admins of AtCoder to give a clear definition of beginners or to avoid overly difficult algorithms in ABCs.

Since my English is pretty poor, please forgive me for the impolite (might be) wording.