Zilina Sudoku [WSC 2009]

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Is this suitable for a Sudoku competition?

Yes
2
15%
Maybe
3
23%
No
8
62%
 
Total votes: 13

detuned
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Zilina Sudoku [WSC 2009]

Post by detuned » Sun 30 Dec, 2018 6:13 pm

Zilina Sudoku [WSC 2009].png
Zilina Sudoku [WSC 2009].png (300.1 KiB) Viewed 2096 times
This (in)famous example was used in the final play-off to determine the World Sudoku Champion in 2009.

The grid features two sorts of "extra regions" - firstly the coloured letter shapes, where numbers placed are not permitted to repeat, and secondly the marked diagonals, which must feature each of the numbers 1-9 (or equivalently must not feature a repeated number).

The main controversial point with this example is that there are many cells in the grid which are only subject to row/column constraints, and there is no third regional constraint. In some sense it could be argued that the diagonals and the letter shapes are additional fourth constraints, rather than regional third constraints on cells.

Mephisto
Posts: 76
Joined: Tue 18 Jan, 2011 12:28 pm

Re: Zilina Sudoku [WSC 2009]

Post by Mephisto » Sun 30 Dec, 2018 6:46 pm

The main controversial point with this example is that there are many cells in the grid which are only subject to row/column constraints, and there is no third regional constraint.
And if you "overlay" a standard 3x3 grid: Is it a Sudoku then? Killer has also such an overlay, KenKen has not (but could be added).

And again: If we accept more than 3 regional constraints (diagonals, windows), why do we not accept less than 3 regional constraints?
and there is no third regional constraint
Not exaclty true, there is a 3rd regional constraint for some cells (but not for all). Same thing for a latin square with diagonals (2D Sudoku).

Must the "3 regional contraints" rule (if we accept it) be valid for all cells or only for a subset of cells? If for all cells, then Zilina and 2D are not Sudokus.

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