Puzzle #858: 2016 Advent Day 9: Knighted Sum Sudoku
Posted December 9, 2016 • #advent2016 #sudoku #numbersoup #sumdoku #knighted #chess
Today I'm presenting a trio of Knighted Sum Sudoku puzzles as the bonus puzzles. One has been waiting in the wings for a while, but the other two are fresh out of my pocket notebook.
Comments
rmsgrey • 12/09/16 7:21 pm
Day 1, taken in isolation, has two possible solutions - if you subtract each number from 10 (so 9 and 1 swap, etc) then you don't change any of the differences between pairs of numbers, so just giving the differences between numbers can't narrow it down to a unique solution (though the 5 can be pinned down).
I'm a bit behind, so I've not yet analysed Day 8 to see whether it resolves the ambiguity in Day 1 - if not, then Day 9 is the first real opportunity to settle it.
rmsgrey • 12/09/16 8:24 pm
On further consideration, I can solve Day 9, but only by ignoring the clue D-across. Unless I've copied something down incorrectly, it gives an inadmissible value for the top row of Day 16...
David Millar • 12/09/16 10:26 pm
Thanks for helping offsky, rmsgrey. As for the D-across clue, I've just checked my hard copy and it seems to be adding up correctly for me. Would you mind scanning and emailing me your current progress or a description of cell contents to try to debug from?
rmsgrey • 12/10/16 4:42 am
Email sent. Current contents of Days 1, 2 and 9, and the reasoning that filled in Day 9.
David Millar • 12/10/16 9:36 am
Thanks rmsgrey. You're correct about clue D-across being incorrect. It should read D7 rather than D3. I've uploaded the correction to this sheet and will include an errata note alongside the next pieces. Sorry for the inconvenience!
offsky • 12/09/16 9:36 am
If Day 1's right column from top to bottom is (hypothetically) 246, does that mean that day 9's bottom row from left to right is 241? Because if that is how the rule is applied, then E-Across and C-Down are causing a conflict. Unless there are two valid solutions to day 1.