Shakashaka

Shakashaka (シャカシャカ) is a logic puzzle developed by publisher Nikoli.[1] The objective is to fill the white squares in a given grid with a pattern of triangles such that each white area in the resulting grid has a rectangular shape. Furthermore, each black square in the grid marked with a number must be orthogonally adjacent to the specified number of triangles.[2]

An example Shakashaka puzzle
The same puzzle with solution marked in teal

Computational complexity

It is NP-complete to decide whether a given Shakashaka puzzle has a solution.[3] Furthermore, counting the number of solutions to a given Shakashaka puzzle is #P-complete.[3]

gollark: Evidently I should use "cardboari" for all my backups.
gollark: It's a very powerful computational cuboid.
gollark: osmarks.net HTMHI™ location 4 has an amazing 768MB of RAM and 12GB of disk space.
gollark: ÆÆÆÆÆÆ?
gollark: This is due to incdec.

References
  1. "Puzzles of nikoli.com". Nikoli. Retrieved 14 August 2014.
  2. "Rules of Shakashaka puzzle". Nikoli. Retrieved 14 August 2014.
  3. Demaine, Erik D.; Okamoto, Yoshio; Uehara, Ryuhei; Uno, Yushi (2014), "Computational complexity and an integer programming model of Shakashaka", IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, E97-A (6): 1213–1219, doi:10.1587/transfun.E97.A.1213, hdl:10119/12147


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