Note on extremal problems about connected subgraph sums

Journal Article (2026)
Author(s)

Stijn Cambie (Katholieke Universiteit Leuven)

Carla Groenland (TU Delft - Discrete Mathematics and Optimization)

DOI related publication
https://doi.org/10.1007/s00373-026-03026-8 Final published version
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Publication Year
2026
Language
English
Journal title
Graphs and Combinatorics
Issue number
2
Volume number
42
Article number
35
Downloads counter
11
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Abstract

For a graph G with vertex assignment c:V(G)→Z+, we define ∑v∈V(H)c(v) for a connected subgraph H of G as a connected subgraph sum of G. We study the set S(G, c) of connected subgraph sums and, in particular, resolve a problem posed by O.-H. S. Lo in a strong form. We show that for each n-vertex graph G, there is a vertex assignment c:V(G)→{1,⋯,12n2} such that for every n-vertex graph G′≇G and vertex assignment c′ for G′, the corresponding collections of connected subgraph sums are different (i.e., S(G,c)≠S(G′,c′)). We also provide some remarks on vertex assignments of a graph G for which all connected subgraph sums are different.