On the Connectivity of the Reddit Community

Here is the link to the paper [pdf].

Abstract: The main statistical result of this paper is that of the reddit users who have upvoted at least one post, 31.4% of them have upvoted only one post and, moreover, have been the only person to upvote it. Conversely, 22.6% of posts which have been voted on at all have received only downvotes and no upvotes. In addition, 67.4% of users are connected in a giant component of upvoting common posts, while 91.4% of posts are connected by having been upvoted by common users.


#1: De Bruijn Sequences

Sequences of 0’s and 1’s

Suppose I want to write a sequence of 0’s and 1’s that contains every possible 2-letter subsequence. This means somewhere in my sequence I need 01, 10, 00, and 11.

Obviously, gluing them all together gives a valid sequence:


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