Reconstruction Algorithm for Permutation Graphs

Abstract

PREIMAGE CONSTRUCTION problem by Kratsch and Hemaspaandra naturally arose from the famous graph reconstruction conjecture. It deals with the algorithmic aspects of the conjecture. We present an $\mbox{\cal O}(n^8)$ time algorithm for PREIMAGE CONSTRUCTION on permutation graphs, where n is the number of graphs in the input. Since each graph of the input has n − 1 vertices and $\mbox{\cal O}(n^2)$ edges, the input size is $\mbox{\cal O}(n^3)$. There are polynomial time isomorphism algorithms for permutation graphs. However the number of permutation graphs obtained by adding a vertex to a permutation graph is generally exponentially large. Thus exhaustive checking of these graphs does not achieve any polynomial time algorithm. Therefore reducing the number of preimage candidates is the key point.