In a social media website (which is probably Twitter, if you are wondering), there are a total
of n users. Each user can follow any number of other users. Let f be a matrix of
relationship between these users, where f[i][j] is either 0 or 1. A 1 indicates
that person i (starting from 0) is following person j, while 0 means otherwise.
This is a companion discussion topic for the original entry at https://algo.monster/problems/twitter_oa_social_network/