# Switching reconstruction of digraphs

**Question**Are there any switching-nonreconstructible digraphs on twelve or more vertices?

To *switch* a vertex of a digraph is to reverse all the arcs incident to it. The digraph so obtained is called a *switching* of the digraph. The collection of switchings of a digraph is called the *switching deck* of . A digraph is *switching-reconstructible* if every digraph with the same deck as is isomorphic to .

The problem is a directed analogue of switching reconstruction of graphs in which one complements the edges at a vertex, instead of reversing each of its incident arcs.

Bondy and Mercier proved an analogue to Stanley's result for switching reconstruction of graphs. They proved that a digraph on vertices is switching-reconstructible if . They also proved many other common results for both switching reconstructions.

One significant difference between the directed and undirected problems is that there exist switching-nonreconstructible directed graphs on eight vertices, while Stanley's conjecture that every simple graph on five or more vertices is switching-reconstructible.

## Bibliography

*[BM] J. A. Bondy and F. Mercier. Switching reconstruction of digraphs. J. Graph Theory 67(2011), no. 4, 332-348.

* indicates original appearance(s) of problem.