## What's wrong with XY-loops?

Advanced methods and approaches for solving Sudoku puzzles

### Re: What's wrong with XY-loops?

SpAce wrote: I guess that means ArtoI can make any claims he wants as long as he makes it clear that he's using his own ranking system which is just one of many.

Do i really have to repeat myself ? Arto's sin was, that he did not publish his rating system (a big sin for a mathematician). You can be very sure, that also according to that a lot of forum puzzles were harder.
It is not true, that ratings are just a matter of taste, especially not for very hard puzzles. What has been done here was to investigate, how hard puzzles are to solve, which are high rated from this or that rating system.

PS: You might have noticed, that champagne calls his list "potentially hardest puzzles". We are all aware, that there can be different points of view. But you can be sure, that a rating, which suggests, that a puzzle is the hardest, which is not top 1000 in this list, is not trustable.
eleven

Posts: 2468
Joined: 10 February 2008

### Re: What's wrong with XY-loops?

Here is a link that shows the closest explanation to ArtoI's rating system. According to his rating, on Oct 3rd 2006 AI Escargot is the top rated puzzle (only by 5 points )

http://www.aisudoku.com/en/AIwME.html

tarek

tarek

Posts: 3748
Joined: 05 January 2006

### Re: What's wrong with XY-loops?

eleven, I'm really not arguing anything to the contrary. My point was purely philosophical, if anything. I'd be happy to see the record set straight. After this discussion started, I actually prompted a friendly reporter to investigate this issue. Unfortunately I didn't get any promises.
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SpAce

Posts: 2674
Joined: 22 May 2017

### Re: What's wrong with XY-loops?

SpAce wrote:
Btw, is everyone else using software solvers nowadays, since I can't seem to find almost any other manual systems published? I'd be really interested in seeing how others solve non-trivial puzzles with just pencil-and-paper and what kind of mark-up they're using. I have my own extreme-capable system, but I'd like to know which parts of it are genuinely original and unique and which are unknowingly reinvented wheels. All I know for sure is that I haven't seen anything like it. Someone might also have ideas that I'd like to adopt.

I still use ordinary puzzle books. The way I mark is: Snyder notation in top corners, all possible candidates for a cell within the middle of the cell. Personally I don't like the ordinary notation of putting each number on the same spot. I find this notation way more efficient at solving puzzles. The only negative I'd say is the fact it's harder to keep track of a candidate appearing exactly 3 times in a box (unless I note these as well) and when filling in the entire puzzle when you're "stuck" it's not really easy to oversee - but I try to avoid those situations.

I guess I'm somewhat out of the ordinary anyway. I really prefer the names "Bent Triple" and "Bent Quadruple +" to any kind of XY(Z)-Wing or Sue de Coq. I find those visual nominations way more representative logic and thus easier to explain the logic to (newer) people. I think the names should visualize the logic as good as possible. Either way I guess everyone has their own nitpicks?
FairyTailed

Posts: 8
Joined: 02 January 2020

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