Spanning Trees Minimizing Geometric Indices¶
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33rd Annual Fall Workshop on Computational Geometry · Nov 13, 2026 To appear
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Abstract¶
A topological index assigns a number to a graph, treating every edge as having unit length. Motivated by the work of Abu-Affash et al. on a geometric analogue of the Wiener index, we study geometric versions of two indices: the mean subtree order and the Hosoya index. Given \(n\) points, the goal is a spanning tree minimizing the index. For the mean subtree order on a line, the sorted path is a tight \(2\)-approximation. In the plane, deciding whether there exists a spanning tree with mean subtree order at most \(\mu_0\) is NP-hard. For the Hosoya index, the optimal star gives an aspect-ratio-sensitive approximation, and it is weakly NP-hard to decide whether a spanning tree has Euclidean Hosoya index at most \(Z_0\) and total Euclidean length at most \(L_0\).