Shakashaka
From HandWiki
Short description: Logic puzzle
An example Shakashaka puzzle
The same puzzle with solution marked in teal
Shakashaka (シャカシャカ) is a logic puzzle developed by publisher Nikoli.[1]
Rules
Shakashaka is played on a rectangular grid of white and black squares. Some black cells may contain a number.
The objective of the puzzle is to place triangles in some of the white cells. There are four kinds of triangles which can be put in squares: 
In the resulting grid,
- The white parts of the grid (uncovered by black triangles) must form a rectangle or a square.
- Black cells with a number must be orthogonally adjacent to the specified number of black triangles.[2]
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]
References
- ↑ "Puzzles of nikoli.com". Nikoli. https://www.nikoli.co.jp/en/puzzles/index.html. Retrieved 18 August 2021.
- ↑ "Rules of Shakashaka puzzle". Nikoli. https://www.nikoli.co.jp/en/puzzles/shakashaka.html. Retrieved 18 August 2021.
- ↑ 3.0 3.1 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, Bibcode: 2014IEITF..97.1213D
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