An ASP-Completeness Framework for Dynasty Puzzles

Abstract

A certain class of pencil-and-paper puzzles shares common rules: given a grid, certain cells must be shaded such that i) no two shaded cells are orthogonally adjacent, and ii) all unshaded cells are orthogonally connected. Such puzzles are sometimes referred to as "dynasty puzzles" within parts of the online puzzle community. We introduce a framework for proving the ASP-completeness (i.e., NP-complete under parsimonious reductions) of various dynasty puzzles. We apply this framework to seven specific dynasty puzzles - Akichiwake, Aquapelago, Ayeheya, Guide Arrow, Heyawake, Hitori, and Kurodoko. As a consequence, for given k solutions of any of these puzzles, deciding whether a distinct solution exists is NP-complete, and counting the number of solutions is #P-complete. Our results strengthen the known result of ASP-completeness for Heyawake and establish the ASP-completeness of the other six puzzles. The main idea is to reconstruct the reduction from the Tree-Residue Vertex-Breaking Problem (TRVB) to the Hamiltonian Cycle Problem introduced by MIT Hardness Group (2024). In our framework, the connectivity of the unshaded cells ensures the connectivity of the shaded cells, allowing the shaded cells to simulate TRVB, which is also an alternative representation of the Hamiltonian cycles under certain conditions.