A linear-time algorithm for finding a paired 2-disjoint path cover in the cube of a connected graph

For a connected graph G=(V(G),E(G)) and two disjoint subsets of V(G)   A={α1,…,αk} and B={β1,…,βk}, a paired (many-to-many) k-disjoint path cover of G joining A and B is a vertex-disjoint path cover {P1,…,Pk} such that Pi is a path from αi to βi for 1≤i≤k. In the recent paper, Park and Ihm (2014) presented a necessary and sufficient condition for a paired 2-disjoint path cover joining two vertex sets to exist in the cube of a connected graph. In this paper, we propose an O(|V(G)|+|E(G)|)-time algorithm that actually finds such a paired 2-disjoint path cover. In particular, we show that, in order to build a desired disjoint path cover, it is sufficient to consider only the edges of a carefully selected spanning tree of the graph and at most one additional edge not in the tree, which allows an efficient linear-time algorithm.