dailysudoku.com

[garytorborg]

It's been a while since I have needed help on one of these. Sticking with just the "fiendish" puzzles on my smartphone sudoku software, I have been able to solve most puzzles in a half hour or less. The exceptions to that have been instances of my error - that is, after getting badly stuck I would try erasing all the pencil marks (leaving the original and solved cells) and start the pencil-mark process again. Often, this would expose an error I previously made. The few previous times it did not, I would post the puzzle on this forum. Such is the case here.

The puzzle is also unusual because, unlike nearly every other "fiendish" puzzle I've done so far, I have found not one single "wing" of any kind that has resulted in an elimination. There are no x-wings (or swordfish, etc.) that I can find in the puzzle that result in any eliminations. (Note, there are three different digits that form the necessary patterns, but all "extra" candidates have been eliminated already by other techniques). There are two xy-wings, neither of which make any eliminations. There is one xyz-wing, same notation. There is a w-wing, but same thing. Like most of these puzzles, there were (past tense intended) several doubles and triples that all resulted in eliminations. But that has left me at this point even after doing the pencil marks twice:

[Marty R.]

There's a Type 1 UR on 38 which removes 38 from r1c3.

I think there's a Sashimi X-Wing on 5 in rows 59 which eliminates 5 from r6c1.

[daj95376]

For completeness, there's a Naked Quad (Hidden Pair) in column 9. I don't think it contributes anything to Marty's solution.

[keith]

You have missed a hidden pair in C9.

The UR reveals a skyscraper on 5 in R59 which leads to an XY-wing -239 which solves it.

Keith