## Nomenclature and definitions

Advanced methods and approaches for solving Sudoku puzzles

### Nomenclature and definitions

I am a beginner to su doku and have had much help from angusj:s document "Solving Sudoku". However, I have some questions. At first I was intrigued with the topic "entering big numbers". To me, a "big number" is a billion or trillion. As English isn't my natural language, I just humbly ask if it shouldn't be "big digits" or "big numerals". If you change the digits yo letters, you wouldn't say "big word" but "big letter".
The other thing is - should there not be restrictions on the X-wing and swordfish? Consider this layout (with 9 as candidates):
Row 1-2: No nines
Row 3 : 9 - 9
Row 4 : - - -
Row 5 : 9 - 9
Row 6-9: no nines
Colunns 5-9: several nines
This works fine.
Now move the pattern down (numerically up) and get:
R0w 1-3: No nines
Row 4 : 9 - 9
Row 5 : - - -
Row 6 : 9 - 9
Row 7-9: No nines
Now this "X-wing" cannot wotk (as I see it), because only one of the nines can be the "real" one.
If you then move it one step to the right, you get:
Row 1-3: No nines
Row 4 : - 9 -|9
Row 5 : - - -|-
Row 6 : - 9 -|9
Row 7-9: No nines
Now it works again

So it seems there should be a restriction that all 4 corners cannot be in the same box.

Extending this to swordfishes, the extreme layout is a 9-block.
As soon as 2 rows are in the same box, I can't see it work, and if it is a real, compact 9-block, 2 must be so that will never work.
I appreciate comments on this (of course it may be self-obvious, but a definition should really note the exceptions as well).
rolferic

Posts: 1
Joined: 22 September 2005

### Re: Nomenclature and definitions

rolferic wrote:I am a beginner to su doku and have had much help from angusj:s document "Solving Sudoku". However, I have some questions. At first I was intrigued with the topic "entering big numbers". To me, a "big number" is a billion or trillion. As English isn't my natural language, I just humbly ask if it shouldn't be "big digits" or "big numerals". If you change the digits yo letters, you wouldn't say "big word" but "big letter".

Sounds right to me, well spotted.

The rest of the solving techniques I'll leave to the experts on this forum.

Luna *Hello and welcome btw*
lunababy_moonchild

Posts: 659
Joined: 23 March 2005

I think you are right in the sense that such a pattern would not be a valid/useable XWing. However, if I understand your grid correctly, I don't think that such a pattern of candidates could ever occur : there must be a 9 in column 1 AND in column 3 therefore, all candidates for the 9's in these two columns cannot be in one box.

But perhaps I am being silly and misunderstanding the situation you describe?
kwdos

Posts: 7
Joined: 25 September 2005