Peggy can get away with false solution #1

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opened this Issue Aug 11, 2016 · 3 comments

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dooglius commented Aug 11, 2016

 (x-posted from my comment on Hacker News) Suppose that in a puzzle there is only one 1 and one 9 that do not overlap in any way (row, column, or 3x3 square). Now, suppose that Peggy comes up with a false solution to the problem which sets both of these tiles to 9. Then, neither the 1 nor the 9 can be picked for the green squares, and so no test of Victor's can disprove Peggy's false solution. This seems easily fixable too: rather than the whole green tiles thing, just allow Victor to query either a row/column/3x3 to prove the solution is a valid sudoku, or query the original filled in tiles, to show that the solution corresponds to the original problem. I've come up with an example (look at the 1 and the 9) and verified this:

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Manishearth commented Aug 11, 2016 • edited

 Good observation! I initially was going to go with having a preset option, but I didn't think it was necessary. Added. Will update post shortly.

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Manishearth commented Aug 11, 2016

 Wait, that solution is totally wrong. Hold on.
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Manishearth commented Aug 11, 2016

 Should be fixed now 😄 Thanks!