Dr. Sudoku Prescribes #85 – Slitherlink
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: Two Rings
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 = 8:00, Master = 12:00, Expert = 24:00
Solution: PDF
Solved it, but had to make a guess around halfway through. I always feel bad when my logic fails, but at least I guessed on the right side of 50/50.
Oh boy, I have not done a slitherlink this hard for a while now. I had to work out why the top left go the way it should for a few steps before the whole thing comes together
While I landed as usual between Master and Expert, I found this puzzle to have a different feel than others on this site so far … it seemed to scream out (half way through) for a need to bifurcate. Maybe I failed to see enough steps ahead in my head, but it was only through the use of two or three such bifurcations that I cracked it.
I dont mind such approach for the toughest of puzzles at all. just a slightly different flavor for this site. I was wondering if others needed to “bif” as well, or if I missed a global constraint clue or other mid-puzzle step.
Thanks for a fun puzzle
TheSubro
This was definitely an attempt to get a very hard puzzle in a rather small space which not many constructors do.
Most people report wanting to guess in the upper-left. That is the key spot to look at. My steps focus on the ring of 1’s which force a lot of path whichever way the 3 goes. Notice the path will contain a segment that goes straight through the UL 111 corner and another that wraps quickly away. There are 4 segments — 2 horizontal and 2 vertical connections one in from the inside UL corner of the “1 ring” — which must be used in either situation. Placing these in finally limits the top to having only one more spot to cross vertically through the 1s. But there are already two ends up there. So loop parity gives you a horizontal crossing of the UL 111 corner and sets the entire neighborhood of the 3.
Certainly more indirect than anything else I’ve posted of the loop puzzles here.
I quite liked this one. After years of solving daily slitherlinks over at Kwon-Tom Loop, it’s rare for me to find a hand-made one where the solution isn’t immediately obvious, but this one managed to be a bit of a challenge. It took me around 4 minutes to solve, no guessing/bifurcation needed.
11:56
Wow, it was tough. And I was lucky to be 4 seconds above Expert. Yes, I also needed some bifurcation, although it should be “logic”, since I didn’t write anything down when bifurcating. Where was that blog post about this thing…
Great theme. It also helped me that I remembered certain patterns about diagonal clues; that’s the opening.
Yet to obtain a breakthrough in this.Very difficult to continue.