Abstract
This note concerns the f-parity subgraph problem, i.e., we are given an undirected graph G and a positive integer value function \({f : V(G) \rightarrow \mathbb{N}}\), and our goal is to find a spanning subgraph F of G with deg F ≤ f and minimizing the number of vertices x with \({\deg_F(x) \not\equiv f(x) \, {\rm mod} \, {2}}\) . First we prove a Gallai–Edmonds type structure theorem and some other known results on the f-parity subgraph problem, using an easy reduction to the matching problem. Then we use this reduction to investigate barriers and elementary graphs with respect to f-parity factors, where an elementary graph is a graph such that the union of f-parity factors form a connected spanning subgraph.
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M. Kano’s research is supported by Grant-in-Aid for Scientific Research of Japan, G.Y. Katona’s research is partially supported by the Hungarian National Research Fund and by the National Office for Research and Technology (Grant Number OTKA 67651 and 78439), J. Szabó’s research is supported by OTKA grants T037547, K60802, TS 049788 and by European MCRTN Adonet, Contract Grant No. 504438.
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Kano, M., Katona, G.Y. & Szabó, J. Elementary Graphs with Respect to f-Parity Factors. Graphs and Combinatorics 25, 717–726 (2009). https://doi.org/10.1007/s00373-010-0878-0
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DOI: https://doi.org/10.1007/s00373-010-0878-0