On the complexity of Slater’s problems

Given a tournament T, Slater’s problem consists in determining a linear order (i.e. a complete directed graph without directed cycles) at minimum distance from T, the distance between T and a linear order O being the number of directed edges with different orientations in T and in O. This paper studies the complexity of this problem and of several variants of it: computing a Slater order, computing a Slater winner, checking that a given vertex is a Slater winner and so on.