From the Foxger’s Den #7: Battleships (Yajilin)

Battleships (Yajilin) by Grant Fikes


or solve online (using our beta test of Penpa-Edit tools; use tab to shift between Battleships placement and line drawing modes.)

This is a “Twisted Tuesday” puzzle variation.

Theme: A Fleet of Clues

Rules: Variation of Battleships rules. Place the fleet of ships in the grid so that no ships touch each other, even diagonally. The grid contains internal clues (a number and an arrow) that show how many ship segments are in the indicated direction. All remaining cells containing neither a ship nor a clue must be able to form a single loop, as in a Yajilin puzzle (see for example here but note the “black square rules” are replaced with battleships placement rules).

Answer String: For each row from top to bottom, enter the number of the first column from the left where a ship segment appears. If the row is empty, enter 0. Enter these numbers as a single string with no separators.

Time Standards (highlight to view): Grandmaster = 2:30, Master = 4:00, Expert = 8:00

Solution: PDF

  • Avatar photo drsudoku says:

    Editorial Note: Our posting of this puzzle does not represent a change in our general attitude about Yajilin (too many clues, mostly repetitive logic, …) from the earlier discussion in Doctor’s Note #9 (see Jack’s comment that matches my thinking well). Here, Grant has taken all the extraneous clues and at least built a novel theme out of them. Identifying larger shapes, not just single squares, also makes the logic much more interesting than what is typically discovered in Yajilin.

  • chaotic_iak says:

    So I solved this in head and clocked 02:43 (if my internal stopwatch runs correctly). Screw the timer. But I’m sure it’s not over four minutes, aka I hit Master time.

    Perhaps being so familiar with this genre (which will appear in my upcoming LMI test) aids me a lot, but solving in head is still terribly difficult. If I did it on paper, I’m pretty sure I can hit under two minutes because it’s pretty much Grant-style: every clue is used and the next step is obvious if you spot it. But enough self-boasting and to the puzzle: it’s a good puzzle, nice and easy. Enough for a Tuesday, and has a very strong Grant-style flavor.

    So…you’re planning to have a variation every Tuesday or a variation whenever you feel like it?

  • Ravi says:

    Excellent puzzle. This is my first time seeing this variation.
    Took 12:33

  • I like the synergy between these two genres. I agree with motris about how the larger regions lead to interesting logic not normally found in Yajilin.

    I also think this might make for an interesting variation on the Battleship board game. It would need to be computer (or referee)-assisted. Each player secretly places their ships on a shared grid. For each overlapping segment (ie both players placed a segment in the same spot), that segment is destroyed immediately. Then, each player designates a direction for the “radar” on each remaining segment to face. The GM then replaces each player’s segments with Yajilin style clues about how many enemy segments are seen in that direction. So, essentially, each player ends up with a grid like yours above where the clues form the player’s fleet, and point at the enemy’s fleet. Play continues from there in normal Battleship fashion (ie guess a square to torpedo, get a hit/miss report). The grid would probably need to be bigger than 10×10 to reduce the possibility of collisions at the beginning. Also, there’s no loop constraint which would make set up intractable.

  • Aaron Chan says:

    While I do not particularly like the genre, there are occasional nice Yajilin out there. There were two posted on Detuned Radio quite a while back where the clues are all on row 1 and column 1. Makes for quite a solving experience, especially the large one.

    • Avatar photo drsudoku says:

      Detuned took that idea from a Japanese constructor who basically made an outside clue only Yajilin variation. I’ve written some of the same. I’m not saying you cannot write one or two good Yajilin. I’m saying 90+% of the ones I’ve seen are not that interesting.

      • Aaron Chan says:

        I was looking for a few more of that style of Yajilin. Where do I find the ones you have written?

        • Avatar photo drsudoku says:

          These were the first that came to mind. At least the concept of “outside clues” only in a Yajilin-like setting. I’ve experimented a couple other ways with Yajilin. I generally think they need a more “Akari-like” look with blockers that go unclued.

        • Avatar photo drsudoku says:

          And if you read Grant’s comments in that old Friday Puzzle post carefully, you’ll see he suggested a way to add a row and column to just put the clues on the outside so it would look completely like a Yajilin variant.

  • skynet says:

    First time attempting this yajilin puzzle.Because of a bit of familiarity with battleships i could complete it.

  • Giovanni P. says:

    That moment when you realize that the clue squares form their own Battleship grid…that’s actually a really cool touch. I see why you consider this fit for GMPuzzles.

  • skynet says:

    And about the hidden post ,the search has been fruitless .The guys 3?!so far who have found out the hidden post and posted the solution too should be gifted with not just 1 book but 2!.Congrats guys.
    I am abandoning the search with imeediate effect and calling it quits.
    Skynet’s defence systems shutting down 🙁

  • Tricia says:

    Ah, I love a good hybrid loop puzzle! I agree that the fleet-shaped clues are dead clever.

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