Outside Nurikabe by Tapio Saarinen

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Outside Nurikabe by Tapio Saarinen


Theme: One, Two

Author/Opus: This is the 3rd puzzle from guest contributor Tapio Saarinen, including one earlier Outside Nurikabe. You can find more of his puzzles on Perplexible.

Rules: In this variation of Nurikabe, the islands are now given outside the grid. These numbers must be placed in the first white island cell encountered in the corresponding direction. Each number represents a distinct island, with a total of 23 islands in this puzzle.

Outside Nurikabe Example by Thomas Snyder

Answer String: Enter the length in cells of each of the black segments (the unnumbered, connected “ocean”) from left to right for the marked rows. Separate each row’s entry from the next with a comma.

Time Standards (highlight to view): Grandmaster = 4:15, Master = 10:00, Expert = 20:00

Note: Follow this link for classic Nurikabe puzzles on this website and this link for other variations on Nurikabe puzzles. If you are new to this puzzle type, here are our easiest Nurikabe puzzles to get started on.

  • Andrew Brecher says:

    I completely forgot about the 23-island constraint until the very end, when I was trying to figure out why I was coming up with multiple solutions. For some reason it seems a little less elegant to force a one-to-one match between clues and islands — even though that’s a requirement for standard Nurikabe. Maybe it’s just me.

    • drsudoku drsudoku says:

      Admittedly the 23-island wording is a little clunky, but the style really works better if one knows outside clues are all distinct islands and every island is represented. Maybe I’ll just change the wording to that if we end up presenting this puzzle style again.

      • Neelix says:

        Yeah I like that wording better, although that is what I took away from the wording that was used. Knowing that though led to some interesting deductions.

        Sbe rknzcyr V jnf engure fhecevfrq ng svefg jura V pnzr gb gur ernyvfngvba gung gur vfynaq ng ebj 8 pbyhza 3 unq gb or gur svefg vfynaq sebz gur evtug bs gung ebj.

        – Neelix

  • John B says:

    It’s also a good and unique puzzle if you add a 24th size-1 island at r8c3 that has no border clue. But don’t add it unconsciously, and then try to input the solution to that one in the answer field of this one, as some of us are in the habit of doing!

    • Neelix says:

      wha? That comment doesn’t make sense in the context of the solution I found. *doublechecks his solution*

      – Neelix

      • John B says:

        If you put in that 24th island and forget to link it to one of the border clues, and you still try to place the 23 clued islands in addition, they will rearrange themselves into a quite different unique solution. chaotic_iak maybe did something similar below.

  • The 23-island rule is indeed analogous to the “every island must be clued” rule in standard Nurikabe. I quite like it myself.

    About the solving process, rot-13’d:

    Nsgre fbyivat gur oernx-vaf va gur gbc-evtug naq obggbz-yrsg pbearef, gurer ner gjb hapyhrq vfynaq pryyf ng ebj rvtug pbyhza guerr, naq ebj guerr pbyhza frira. Obgu pryyf zvtug unir rvgure n ebj be n pbyhza pyhr, naq na rneyvre vgrengvba bs gur chmmyr erdhverq rknzvangvba bs juvpu pyhr vf cbffvoyr.

    Yngre ba va gur chmmyr, gur pbyhza pyhr sbe ebj rvtug pbyhza guerr jvyy or oybpxrq, juvpu zrnaf vgf pyhr vf pyhr vf gur ebj pyhr, juvpu nyybjf lbh gb funqr va gur erfg bs gur ebj.

    Nobhg guerr dhnegref va, gurer jvyy or na hapyhrq vfynaq pryy ng ebj frira pbyhza fvk. Gur vagraqrq fbyivat cngu pbagvahrf ol abgvpvat gung gur bayl pyhr gung pna uvag ng guvf pryy vf gur ybjre gjb bs gur nqwnprag pbyhza. Gur fnzr xvaq bs unccraf jvgu ebj frira pbyhza avar naq ebj svir pbyhza avar.

  • Aaron Chan says:

    This one was pretty hard, I must admit. Anyways, I forgot where, but somewhere I reached a spot where I found “n pryy gung pnaabg or na vfynaq fvapr nyy gur ebj/pbyhza pyhrf ner gbb sne njnl ertneqyrff bs jurer V cynpr gurz”, which helped a lot.

  • chaotic_iak says:


    Oops, I missed that R8C3 is clued by some particular clue that forces a long string of oceans.

    Great puzzle. The variant is redone in a completely new flavor with the abundance of islands now.

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