Edge cycle cover

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File:Edge cycle cover.svg
An edge cycle cover for each graph, where vertices and edges are shaded according to the cycle they are a part of, and are blended if they are a part of multiple cycles.

In graph theory, a branch of mathematics, an edge cycle cover (sometimes called simply cycle cover[1]) of a graph is a family of cycles which are subgraphs of G and contain all edges of G.

If the cycles of the cover have no vertices in common, the cover is called vertex-disjoint or sometimes simply disjoint cycle cover. In this case, the set of the cycles constitutes a spanning subgraph of G.

If the cycles of the cover have no edges in common, the cover is called edge-disjoint or simply disjoint cycle cover.

Properties and applications

Minimum-Weight Cycle Cover

For a weighted graph, the Minimum-Weight Cycle Cover Problem (MWCCP) is the problem to find a cycle cover with minimal sum of weights of edges in all cycles of the cover.

For bridgeless planar graphs, the MWCCP can be solved in polynomial time.[2]

Cycle k-cover

A cycle k-cover of a graph is a family of cycles which cover every edge of G exactly k times. It has been proven that every bridgeless graph has cycle k-cover for any even integer k≥4. For k=2, it is the well-known cycle double cover conjecture is an open problem in graph theory. The cycle double cover conjecture states that in every bridgeless graph, there exists a set of cycles that together cover every edge of the graph twice.[3]

See also

References

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  1. Cun-Quan Zhang, Integer flows and cycle covers of graphs, Marcel Dekker,1997.
  2. "Handbook in Graph Theory" (2004) Template:Isbn, p. 225
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