(1+epsilon)-Distance Oracle for Planar Labeled Graph

TL;DR

This paper introduces a (1+epsilon)-approximate distance oracle for planar vertex-labeled graphs that balances space and query time, enabling efficient shortest path length queries with controlled stretch.

Contribution

It presents a novel oracle construction for planar graphs that achieves near-linear space and fast query times for vertex-label shortest path queries with a small stretch.

Findings

Space complexity is O((1/epsilon) * n * log n).

Query time is O((1/epsilon) * log n * log rho).

For rho = O(log n), query time reduces to O(log n).

Abstract

Given a vertex-labeled graph, each vertex $v$ is attached with a label from a set of labels. The vertex-label query desires the length of the shortest path from the given vertex to the set of vertices with the given label. We show how to construct an oracle if the given graph is planar, such that $O(\frac{1}{\epsilon}n\log n)$ storing space is needed, and any vertex-label query could be answered in $O(\frac{1}{\epsilon}\log n\log \rho)$ time with stretch $1+\epsilon$. $\rho$ is the radius of the given graph, which is half of the diameter. For the case that $\rho = O(\log n)$, we construct an oracle that achieves $O(\log n)$ query time, without changing the order of storing space.