Sudoku Variants Series (166) - External Sudoku
(Published on 31. January 2017, 00:00 by Richard)
External Sudoku
Inspiration for this variant comes from Sudoku Cup #5
Solve online in Penpa+ (thx Nick Sirnov!)
Place the digits from 1 to 9 in every row, column and 3x3-block. Also fill in the gray cells with numbers 1-7 so that no number is repeated within an edge of the shaded square. The difference of each pair of numbers placed in diagonally adjacent shaded cells must be at least 2.
Solution code: Row 1, followed by column 1.
Comments
on 10. August 2022, 06:12 by Richard
Added link and tag for online solving. Thx Nick!
on 29. August 2021, 20:40 by Nick Smirnov
Penpa:
https://git.io/JEoxP
on 29. August 2021, 13:45 by Nick Smirnov
@Richard, great, thank you. It seems that I completely misunderstood the rules, lol. I confused the shaded square with a shaded cell (the mistake that even native English speakers frequently do) and thought that each shaded CELL must have different orthogonally adjacent neighbours. That explains why I broke the puzzle and backtracking didn't detect any mistakes.
on 29. August 2021, 12:39 by Nick Smirnov
@Richard, could you, please, explain me what does this part of the rules mean? No number is repeated within an edge of the shaded square.
Does it mean that, for example, R3C2 must be different from R4C1? And that R4C1 must be different from a digit in the shaded square outside of the grid which has a common edge with R4C1?
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Sure!
See the grey cells as a diamond.
Each of the four diagonal sides of the diamond contains the digits 1-7 exactly once. The difference between two (diagonally) neighbouring digits on the sides of the diamond must be at least two. (I.e. non-consecutive). This rule doesn't affect digits in white cells, also not the ones that touch the diamond shape.
For example: the two remaining digits on the right side outside the grid may not be 3, 4 or 5.
on 31. January 2017, 13:29 by marcmees
nicely constructed
