LITS
LITS, formerly known as Nuruomino (ヌルオミノ), is a binary determination puzzle published by Nikoli.[1]
Rules
[edit]LITS is played on a rectangular grid, typically 10×10; the grid is divided into polyominoes, none of which have fewer than four cells. The goal is to shade in a tetromino within each pre-printed polyomino in such a way that no two matching tetrominoes are orthogonally adjacent (with rotations and reflections counting as matching), and that the shaded cells form a valid nurikabe: they are all orthogonally contiguous (form a single polyomino) and contain no 2×2 square tetrominoes as subsets.
History
[edit]The puzzle was first printed in Puzzle Communication Nikoli #106; the original title is a combination of 'nuru' (Japanese: "to paint") and 'omino' (polyomino). In issue #112, the title was changed to the present one, which represents the four (of five) tetrominoes used in the puzzle: the L-shape, the straight, the T-shape, and the skew (square tetrominoes may never appear in the puzzle as they are a direct violation of the rule).
Complexity
[edit]Testing whether a given LITS puzzle has a solution is NP-complete.[2]
See also
[edit]References
[edit]- ↑ Nikoli's English page on LITS
- ↑ Biro, Michael; Schmidt, Christiane, "Computational complexity and bounds for Norinori and LITS", EuroCG 2017, Malmö, Sweden, April 5–7, 2017 (PDF)
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