# Heavy cycles in weighted graphs

• Volume: 22, Issue: 1, page 7-15
• ISSN: 2083-5892

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## Abstract

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An (edge-)weighted graph is a graph in which each edge e is assigned a nonnegative real number w(e), called the weight of e. The weight of a cycle is the sum of the weights of its edges, and an optimal cycle is one of maximum weight. The weighted degree w(v) of a vertex v is the sum of the weights of the edges incident with v. The following weighted analogue (and generalization) of a well-known result by Dirac for unweighted graphs is due to Bondy and Fan. Let G be a 2-connected weighted graph such that w(v) ≥ r for every vertex v of G. Then either G contains a cycle of weight at least 2r or every optimal cycle of G is a Hamilton cycle. We prove the following weighted analogue of a generalization of Dirac's result that was first proved by Pósa. Let G be a 2-connected weighted graph such that w(u)+w(v) ≥ s for every pair of nonadjacent vertices u and v. Then G contains either a cycle of weight at least s or a Hamilton cycle. Examples show that the second conclusion cannot be replaced by the stronger second conclusion from the result of Bondy and Fan. However, we characterize a natural class of edge-weightings for which these two conclusions are equivalent, and show that such edge-weightings can be recognized in time linear in the number of edges.

## How to cite

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J. Adrian Bondy, et al. "Heavy cycles in weighted graphs." Discussiones Mathematicae Graph Theory 22.1 (2002): 7-15. <http://eudml.org/doc/270548>.

@article{J2002,
abstract = {An (edge-)weighted graph is a graph in which each edge e is assigned a nonnegative real number w(e), called the weight of e. The weight of a cycle is the sum of the weights of its edges, and an optimal cycle is one of maximum weight. The weighted degree w(v) of a vertex v is the sum of the weights of the edges incident with v. The following weighted analogue (and generalization) of a well-known result by Dirac for unweighted graphs is due to Bondy and Fan. Let G be a 2-connected weighted graph such that w(v) ≥ r for every vertex v of G. Then either G contains a cycle of weight at least 2r or every optimal cycle of G is a Hamilton cycle. We prove the following weighted analogue of a generalization of Dirac's result that was first proved by Pósa. Let G be a 2-connected weighted graph such that w(u)+w(v) ≥ s for every pair of nonadjacent vertices u and v. Then G contains either a cycle of weight at least s or a Hamilton cycle. Examples show that the second conclusion cannot be replaced by the stronger second conclusion from the result of Bondy and Fan. However, we characterize a natural class of edge-weightings for which these two conclusions are equivalent, and show that such edge-weightings can be recognized in time linear in the number of edges.},
author = {J. Adrian Bondy, Hajo J. Broersma, Jan van den Heuvel, Henk Jan Veldman},
journal = {Discussiones Mathematicae Graph Theory},
keywords = {weighted graph; (long, optimal, Hamilton) cycle; (edge-, vertex-)weighting; weighted degree},
language = {eng},
number = {1},
pages = {7-15},
title = {Heavy cycles in weighted graphs},
url = {http://eudml.org/doc/270548},
volume = {22},
year = {2002},
}

TY - JOUR
AU - Hajo J. Broersma
AU - Jan van den Heuvel
AU - Henk Jan Veldman
TI - Heavy cycles in weighted graphs
JO - Discussiones Mathematicae Graph Theory
PY - 2002
VL - 22
IS - 1
SP - 7
EP - 15
AB - An (edge-)weighted graph is a graph in which each edge e is assigned a nonnegative real number w(e), called the weight of e. The weight of a cycle is the sum of the weights of its edges, and an optimal cycle is one of maximum weight. The weighted degree w(v) of a vertex v is the sum of the weights of the edges incident with v. The following weighted analogue (and generalization) of a well-known result by Dirac for unweighted graphs is due to Bondy and Fan. Let G be a 2-connected weighted graph such that w(v) ≥ r for every vertex v of G. Then either G contains a cycle of weight at least 2r or every optimal cycle of G is a Hamilton cycle. We prove the following weighted analogue of a generalization of Dirac's result that was first proved by Pósa. Let G be a 2-connected weighted graph such that w(u)+w(v) ≥ s for every pair of nonadjacent vertices u and v. Then G contains either a cycle of weight at least s or a Hamilton cycle. Examples show that the second conclusion cannot be replaced by the stronger second conclusion from the result of Bondy and Fan. However, we characterize a natural class of edge-weightings for which these two conclusions are equivalent, and show that such edge-weightings can be recognized in time linear in the number of edges.
LA - eng
KW - weighted graph; (long, optimal, Hamilton) cycle; (edge-, vertex-)weighting; weighted degree
UR - http://eudml.org/doc/270548
ER -

## References

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2. [2] J.A. Bondy, Basic graph theory: paths and circuits, in: R.L. Graham, M. Grötschel and L. Lovász, eds., Handbook of Combinatorics (North-Holland, Amsterdam, 1995) 3-110. Zbl0849.05044
3. [3] J.A. Bondy and G. Fan, Optimal paths and cycles in weighted graphs, Annals of Discrete Math. 41 (1989) 53-69, doi: 10.1016/S0167-5060(08)70449-7. Zbl0673.05056
4. [4] J.A. Bondy and G. Fan, Cycles in weighted graphs, Combinatorica 11 (1991) 191-205, doi: 10.1007/BF01205072. Zbl0763.05051
5. [5] J.A. Bondy and S.C. Locke, Relative lengths of paths and cycles in 3-connected graphs, Discrete Math. 33 (1981) 111-122, doi: 10.1016/0012-365X(81)90159-X. Zbl0448.05044
6. [6] J.A. Bondy and U.S.R. Murty, Graph Theory with Applications (Macmillan, London and Elsevier, New York, 1976). Zbl1226.05083
7. [7] G.A. Dirac, Some theorems on abstract graphs, Proc. London Math. Soc. (3) 2 (1952) 69-81, doi: 10.1112/plms/s3-2.1.69. Zbl0047.17001
8. [8] L. Pósa, On the circuits of finite graphs. Magyar Tud. Akad. Mat. Kutató Int. Közl. 8 (1963) 355-361. Zbl0133.16702
9. [9] T. Spencer (Personal communication, 1992).
10. [10] Yan Lirong (Personal communication, 1990).

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