Partitions of Graphs into Trees
In this paper, we study the k-tree partition problem which is a partition of the set of edges of a graph into k edge-disjoint trees. This problem occurs at several places with applications e.g. in network reliability and graph theory. In graph drawing there is the still unbeaten (n − 2) ×(n − 2) area planar straight line drawing of maximal planar graphs using Schnyder’s realizers , which are a 3-tree partition of the inner edges. Maximal planar bipartite graphs have a 2-tree partition, as shown by Ringel . Here we give a different proof of this result with a linear time algorithm. The algorithm makes use of a new ordering which is of interest of its own. Then we establish the NP-hardness of the k-tree partition problem for general graphs and k ≥ 2. This parallels NP-hard partition problems for the vertices , but it contrasts the efficient computation of partitions into forests (also known as arboricity) by matroid techniques .
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