A more difficult slitherlink

This one is the same variant as I described previously: all the numbers are outside the loop. This one is larger at least. I don’t know whether it’s actually more difficult other than that.

One aspect I particularly appreciate of well-designed slitherlink puzzles (and this type of puzzle in general: masyu, nurkabe, fillomino and others) is that there is only one solution. This leads to the interesting solving technique that if a proposed addition to the work-in-progress leads to a situation where there are two ways to fill in a section and both are equivalent, then the proposed addition must be wrong, because there cannot be two solutions. This technique is particularly hard to apply, but I’d be very interested in a puzzle that required extensive application of it to find the solution.

In any case, here’s the puzzle. Check the previous post if you don’t know the general rules for a slitherlink.




3 thoughts on “A more difficult slitherlink

  1. FadedOasis

    Okay, this one’s a bit harder than your last. 63 minutes for me, mostly because I kept getting tricked by specific areas without realizing until it was too late.

    Nicely designed.

    –ih8evilstuff on reddit

  2. Peter

    Ordinarily, I prefer not to assume uniqueness, since I like to know whether or not a puzzle setter made his solution unique, and to find all solutions if he didn’t. That said, yours is a particularliy good example of when that shortcut can be applied from the very start.

    In the lower right, the 0, 1, and the other two cells adjacent to both are clearly outside. If the cell below the 1 is inside, then there is no way to know if the corner is inside or outside. Therefore, if the solution is unique, both of those are outside and there is a fence between the one and the cell to its left.

    1. gcanyon Post author

      Nice deduction about the cell below the 1. That’s exactly the sort of deduction I find fascinating about the “solution must be unique” aspect. Part of the specification of this slitherlink is that all the numbers are outside, so yes, the 1 and the 0 (and the two cells adjacent to both of them) must be outside.


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