On a directed variation of the 1-2-3 and 1-2 Conjectures

In this paper, we consider the following question, which stands as a directed analogue of the well-known 1-2-3 Conjecture: Given any digraph D with no arc uv verifying d(u) = d(v) = 1, is it possible to weight the arcs of D with weights among {1, 2, 3} so that, for every arc uv of D, the sum of incident weights out-going from u is different from the sum of incident weights in-coming to v?We answer positively to this question, and investigate digraphs for which even the weights among {1, 2} are sufficient. In relation with the socalled 1-2 Conjecture, we also consider a total version of the problem, which we prove to be false. Our investigations turn to have interesting relations with open questions related to the 1-2-3 Conjecture. © 2016 Elsevier B.V. All rights reserved.