Dr. Sudoku Prescribes #49 – Slitherlink

Slitherlink by Thomas Snyder


or solve online (using our beta test of Penpa-Edit tools in edgex mode where left click+drag draws lines and right click marks X’s)

Theme: Parquet

Rules: Standard Slitherlink rules.

Answer String: Enter the length in cells of each of the internal loop segments from left to right for the marked rows, starting at the top. Separate each row’s entry with a comma.

Time Standards (highlight to view): Grandmaster = 0:45, Master = 1:15, Expert = 2:30

Solution: PDF

  • skynet says:


  • TheSubro says:

    A few thoughts:

    1. While I have often criticized the use of truly beginner puzzles on blogs like this, Skynet’s constant comments and innocent expressions of less than expert times supports the idea that with a wide range of puzzles Tom (along with his name and recognition) may act to draw in others to this world.

    2. On the other end of the spectrum, I am truly amazed at the speed that some people can solve these puzzles. I, like most who have done these slitherlinks, ran through this one in just under two minutes. It was obviously a very straightforward slitherlink beginner puzzle with a number of 33 and 30 combinations. I never had to even pause for a second to consider the path. With that said, I do not know if I could have physically drawn in the solution in 45 seconds, even if I was tracing it from below. I almost feel like there are those amongst the best at this in the world who are like the Flash superhero in DC Comics with their pens. Curious to know if others feel the same, or if there is something I – as the perennial snail around these parts – am missing.

    3. Tom, thanks for the hidden times. First, it acts in some ways like a Xmas present – when you do the puzzle and then get to look to uncover how you did as compared to others. It also does not bias my thoughts on the puzzle ahead of doing it. I recognize that I could avoid the times when posted if I wanted to go out of my way. This just helps my self-control, so its much appreciated for all these reasons.

    Thanks for it all.


    • Jack Bross says:

      I always feel like there are physical limitations on speed for me on puzzles like this. On Nikoli and Croco-Puzzle, I generally can’t accurately drag the loop around quickly enough to be near the top on a true sprint puzzle like this. Some of that is possibly just being over 40. I think that’s one reason why although I have plenty of Croco-Puzzle results in the top 30 or so, routinely in some genres, I am never in the top 10. My biggest problem with Slitherlink in particular though is for most puzzles I still feel like I need to x-out a lot of “no segment here” notations, and that’s slow. (Not an issue with this one)

      I feel like a have a weird relationship with estimated solving times depending on the type of puzzle. For Sudoku, for instance, I’m very slow on “easy” puzzles — it takes at least 3-4 minutes for me to solve any 9×9 Sudoku no matter how easy. But for the puzzles where the average solving time is 10-15 minutes, I’m suddenly much more competitive. For a genre like Slitherlink, I’m slow at all levels. With Masyu, I’m pretty fast at all levels. Shrug.

      Also, I would like to say that while this is an easy introduction to Slitherlink, it is definitely a nicely designed, fun to solve puzzle even for experienced solvers. Well-made “easy” puzzles get under-appreciated, I think.

      • TheSubro says:

        I too have crested the big 4-0, actually I turn 49 in June. I may get thrown out of the club around here any day now (“Logan’s Run” comes to mind). I certainly appreciate the fact that you and I are probably well above the age of the average puzzler and that may be a factor. The good news is that this also probably keeps our minds young.

        I must admit that I too default back to using too many X’s along the way as guidelines, and that may be a factor I had not considered.

        The one thing I have come to appreciate too is that some people that do this stuff just see “the whole board” better than others, and that must be a factor as well. Thanks for chiming in though.


      • Avatar photo drsudoku says:

        There are definitely elements of manual dexterity that come into play in solving puzzles fast. Another is what I’ll call “look ahead” ability — having your eyes scanning a little bit even as your pencil is marking the 03 clue.

        I find a big difference between online and paper times (I only ever practice speed on paper and my trackball timing is very bad). I too have tried to redraw some of the loops knowing the answers in the winning time on Croco-puzzle and have not been able to do it.

        • Para says:

          Online solves are far more helped my dexterity though I think as there’s general more need to be very accurate. You won’t accidentally place an extra line segment, colour the wrong square or hit the wrong number on paper, but it’s easily done in online applets.

      • Scott Handelman says:

        Jeez Louise, Jack, your response is pretty much an exact duplicate of my assessment of my own puzzle ability: slow at Slitherlink because I overmark the grid, slow at Sudoku in general, fast at puzzles like Masyu. No wonder we tied at USPC this year…I’m getting the sense that you’re my puzzle doppelganger.

        • TheSubro says:

          Let me add to this humorous post by mentioning something that I have not been able to share with anyone (cause no one would care or understand) since August … I hate both of you (Jack and Scott).

          I scored 145 on the USPC and the two of you scored 146s. You two tied for the top 25, and in turn kept me out of it. (Mine was unofficial as I was unable to do it when the official competition ran, but in my head I knew that was my goal and I failed because of your 1 point better scores).

          But, there is always next year (although Scott, you are much younger than me (and Jack) and have a few more good years left in your tank).


        • Scott Handelman says:

          I was about to ask how you know how old I am, but I guess my picture is right there next to my name.

  • TheSubro says:

    My old eyes can’t see that little picture, even with my reading glasses on (another handicap that no one cares about).

    The internet is a powerful tool though. Your website at the school where you teach math implies your age. Jack, by the way, is also a math teacher, so … other than the age thing you two may have in fact been separated at birth.

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