I’ve been reading up on advanced solving techniques in order to add a few links in the solving techniques index that I stuck on top of the solving sudoku forum.
Many of these techniques are blending into each other and the resulting picture is not a bunch of “Weird Crap” as Angus (and others) call it, but an excellent addition to the current set of techniques. If only people would not come up with these weird names, the techniques would be taken much more seriously by the larger community. Bennys seems to have given up promoting his techniques, Carcul is vigorously promoting them and Jeff does not make appearances in the programmers forum.
So, what are these weird crap techniques?
- BUG (Bivalue Universal Grave)
- BUG-Lite
- MUG (Myth Jellies invented this)
- ALS (Almost Locked Sets)
- AUR (Almost Unique Rectangles)
- Nice Loops
- Turbot Fish
- Fishy Cycle
- Filet-O-Fish (Finned X-Wing or Swordfish)
- Filet-of-Anything
- Sashimi Observation (Almost Finned X-Wing or Swordfish)
- Sushi Presentation Rule (POM applied to Sashimi)
- Broken Wings (with guardians)
- Pattern Overlay Method (similar to templating)
- X-Chains (nice loops, covers turbot-fish and simple coloring)
- X-Cycle
- XY-Chains
- XY-Cycles (nice loops)
- Grouped X-Chains (part of nice loops)
- Grouped Turbot Fish
- Skyscraper and Extended Skyscraper
- 2-String Kite (Blades)
- Advanced Colouring
- Multi-Colouring
- Double Chain
- Combination Nice Loop
- Super-Colouring
- 3D-Medusa (Bob Hanson)
- APE (Aligned Pair Exclusions) and APE 2
- Unique Rectangles types 1-8 (list is still growing)
- Traveling Pairs (Braiding analysis)
- Template checks (Nishio)
- Almost Nice Loops (ANL)
A lot of these techniques are rooted in the discovery of Turbot Fish by Nick70 in the summer of 2005. This has sprung a whole new subclass of techniques, which is still growing, reinvented, relabeled, subdivided, etc.
I have already implemented a number of these techniques in SudoCue.