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arXiv · 2603.22456

ETH Flippers Approach to Parallel Reconfiguration of Triangulations: SAT formulation and Heuristics

Lorenzo Battini·Marko Milenković
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Abstract

We describe the algorithms used by the ETH Flippers team in the CG:SHOP 2026 Challenge. Each instance consists of a set of triangulations on a common point set, and the objective is to find a central triangulation that minimizes the total parallel flip distance to the input set. Our strategy combines an exact solver for small and medium-sized instances with a suite of heuristics for larger instances. For the exact approach, we formulate the problem as a SAT instance with XOR clauses to model edge transitions across multiple rounds, further optimized by lower bounds derived from exact pairwise distances. For larger instances, we use a greedy local search and edge-coloring techniques to identify maximal sets of independent flips. Our approach ranked second overall and first in the junior category, computing provably optimal solutions for 186 out of 250 instances.

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Lorenzo Battini, Marko Milenković. 2026-03-23. ETH Flippers Approach to Parallel Reconfiguration of Triangulations: SAT formulation and Heuristics. https://arxiv.org/abs/2603.22456

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