From the Foxger’s Den #39: Battleship Sudoku

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Battleship Sudoku by Grant Fikes


This is a “Twisted Tuesday” puzzle variation.

Theme: No Radar!

Rules: Standard Battleship Sudoku rules. However, there is no radar (no outside battleships clues).

Answer String: Enter the 5th row from left to right, followed by a comma, followed by the 5th column from top to bottom.

Time Standards (highlight to view): Grandmaster = 1:45, Master = 2:30, Expert = 5:00

  • FoxFireX says:

    Neat little puzzle, but I’m a little curious if I made a wrong assumption somewhere, because I didn’t actually hfr nal bs gur fhoznevar pyhrf nf cneg bs gur fbyir.

    • Aaron Chan says:

      Unless I am wrong, you do need to submarine clues. With different numbers on the submarines, you can change the location of the 2 destroyers around and still get a valid grid.

  • Aaron Chan says:

    May I ask whether anyone have an effective notation for battleship sudoku? Shading the cell then writing on top of it makes it hard to read.

    • I use underlined numbers for seas and I draw circles around ship segment numbers. Sometimes it gets confusing when a circled number is a sub vs. circling several adjacent numbers to be a bigger ship; when I’m worried about that I put squares around known ship segments and use circles for the subs. Then I sort of merge the squares into an oval thing when I know where the ship ends are.

  • Joe F. says:

    I seem to have found a second solution, and for the life of me I can’t figure out what’s wrong with it. In fact, it has the advantage of placing every ship uniquely as well.

    But I’m only a novice, so there might be a rule I’m breaking unawares.

    By column (ships in bold):

    346152, 263541, 152463, 415236, 531624, 624315

    • Tamz29 says:

      Bottom row’s 2 is a sea

      • Joe F. says:

        My listed numbers are the columns. All of my 2+ ships ended up in columns, so I thought it would be easier to express the solution that way.

        • Fred C says:

          The point, though, is that any given number in a Battleship Sudoku is a sea. So your placement of the 3 ship in column 2 is invalid, because the 3 in that column is a given, and therefore a sea.

        • Joe F. says:

          Ah Fred, that’s the rule I missed. Thank you! I won’t forget that one in the future.

    • hagriddler says:

      Found the exact same alternate solution and missed the same rule completely…

      “Digits inside the grid at the start should be treated like “seas” and cannot belong to ships in the fleet.”

      • John Reid says:

        Me too! I actually spent a few HOURS struggling with this, trying to find a way to crack it, before just giving up and guessing out of frustration. I have no idea how I didn’t know this rule before (I guess I haven’t played enough Battleship Sudoku) but I’m sure I won’t forget it after this ordeal!

  • chaotic_iak says:


    Great puzzle, although I definitely question the Tuesday difficulty. Finding the largest ship, followed by later packing all the remaining ships together, doesn’t seem like a Tuesday puzzle (more like Wednesday/Thursday). Perhaps because of the 6×6 size?

    The theme is neat too. I actually am more inclined to say “consecutive givens” as the theme than “no radars”, but heh, two themes in one is great 😀

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