Domino Tatami Tiling is NP-Complete

Alejandro Erickson, Department of Computer Science, University of Victoria, Canada.
Frank Ruskey, Department of Computer Science, University of Victoria, Canada.

Abstract:

A covering with dominoes of a rectilinear region is called tatami if no four dominoes meet at any point. We describe a reduction from planar 3SAT to Domino Tatami Covering. As a consequence it is therefore NP-complete to decide whether there is a perfect matching of a graph that meets every 4-cycle, even if the graph is restricted to be an induced subgraph of the grid-graph. The gadgets used in the reduction were discovered with the help of a SAT-solver.


The shape below is an rectilnear region (with holes). It has been tatami tiled with dimers. Other rectilear regions can not be tatami tiled with dimers. In this paper we show that the decision problem is NP-complete.

Here's an illustration from the paper of an example of the reduction.



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