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The following Sudoku has a nice little twist: after solving, use the numbers in the green squares as a basis for a Nurikabe puzzle. You can create a new grid for the Nurikabe (a 9x9 grid with the numbers from the green squares in the corresponding squares), or solve it right on top of the Sudoku. The rules of a Nurikabe are (source):

  • All of the black cells must be connected.
  • Each numbered cell must be part of a green island of connected green cells.
  • Each island must have the same number of green cells as the number it contains (including the numbered cell).
  • Two islands may not be connected.
  • There cannot be any 2x2 blocks of black cells.

sudoku grid with some squares green for nurikabe

This is a pretty simple puzzle, but I liked the idea of it and wanted to put it out there. Inspired by the current FTC: Wacky Sudokus, but unfortunately more applicable to a previous one.

Image transcription

Nurikabe taken from (spoiler for nurikabe, obviously):

https://www.logicgamesonline.com/nurikabe/archive.php?pid=241

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    $\begingroup$ Taking puzzles from other sources, especially autogenerated ones (which I think that source does) is frowned upon here. Even if it's just part of another puzzle. $\endgroup$
    – bobble
    Jan 13, 2021 at 18:40
  • $\begingroup$ @bobble Oh, my bad - I thought the issue was uncredited puzzles, and was hoping this would count as a "fair use". Should I delete it? $\endgroup$
    – samm82
    Jan 13, 2021 at 18:43
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    $\begingroup$ It's allowed, and I'm not the person to ask about legal matters. However, people may give less upvotes if they think less original work was put into the puzzle. $\endgroup$
    – bobble
    Jan 13, 2021 at 18:45
  • $\begingroup$ @bobble Yeah, that's fair - I really wanted to have it so that you would need to solve the Sudoku and Nurikabe in parallel (so a number in the Sudoku would need to be deduced from its context in the Nurikabe), but I couldn't manage to do it and wanted to get the idea out there in the hopes of inspiring someone else to make a better one :) $\endgroup$
    – samm82
    Jan 13, 2021 at 18:51
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    $\begingroup$ Fair enough! I think it would be very hard to somehow use the nurikabe to be be able to clue numbers in the sudoku, but it’s a very interesting concept $\endgroup$
    – Beastly Gerbil
    Jan 13, 2021 at 19:14

1 Answer 1

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The Sudoku

(Will try and put into excel and clean up the images when I have the time)

Starting off, we can make some quick and easy deductions:

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There are some easy 2s that can be placed and the top row which is already mostly solved can also be completed

Moving on, there are a lot of hidden singles throughout the grid

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There are a lot of hidden singles, especially in the middle. After 4 or 5 are found, the rest of the middle rows can be completed

Even more hidden singles later...

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At this point there are lots of easy hidden singles to spot, and the grid is becoming a lot easier to solve. After this point the rest is trivial.

And the solution:

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Finishing off the rest gives us the answer.

The Nurikabe

Keeping the numbers and filling in the obvious cells gets us this starting point:

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Completing the 1s gives us an easy start point

Now in the bottom left...

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There are a lot of unreachable cells at the bottom left of the grid. Filling in those allows us to complete the three, by looking at where an island must be to prevent a 2x2 square.

Moving right...

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The 2x1 island in the middle left must belong to the 7, and this can only be done in one way.

Continuing onwards...

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To prevent a 2x2 square in the middle, the 6 must extend downwards. It cannot belong to the 5, as that would isolate a cell.

Almost there!

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The bottom right path must extend round as such. After this the solution is in sight!

And the solution:

enter image description here

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