Questions: how to design a unique sudoko? ie how do you know which numbers to fix?
Sunday 15 February 2009
A sudoku puzzle
Pavan and I solved this sudoko today, using the usual rules of engagement until we got to a point where every square had two possible options. Finally, we just picked one, and went as far as we could with that until we reached the same impasse. Each time we made one of these decisions, we labelled the ensuing numbers with a symbol, hence the circles, squares, triangles and diamonds (in that order). Each time, we thought we would hit a contradiciton and the whole thing would unravel until the last incorrect decision. To our surprise, everything worked out, despite the fact that we made four guesses. In the end, we checked the answers, and saw that our solution differed to the published one in the first and last three rows. In the first three rows, our 2s and 4s were swapped with the published answer, and in the last three rows, our 1s and 7s were all swapped. So go figure. I thought sudoko answers were unique.
Questions: how to design a unique sudoko? ie how do you know which numbers to fix?
Questions: how to design a unique sudoko? ie how do you know which numbers to fix?
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Indeed, it seems to have several solutions, nice catch... According to the rules of Sudoku that I read somewhere, this is not a Sudoku then, as it should ahve unique solution. There is a variant where the main diagonals should have 1-9 also, but here the published solution doesn't fulfill that either... So let's sue the Helsinki Times for the lost time and nerves and for causing pain and sorrow... If facebook has caused the murder of a person already, it's easy to imagine that Sudoku can also cause physical and emotional harm and can destroy marriages and friendships... How can they be so irresponsible, I don't understand... ;-)
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