The New Sudoku Players' Forum

[RedNectar]

Hi all,
I'm trying to get my head around the Sudoku terminology, and understand Naked Subsets and Hidden subsets, but have never seen a term that describes the situation where a cell is a member of two sets of locked candidates. In the puzzle below, digit 9 is a candidate for all the free cells in box 7, but ...

* there is a pointing pair in cells D9 & F9, so 9 can be eliminated from cells G9, H9, I9
* there is a pointing pair in cells A4 & A6, so 9 can be eliminated from cells A1, A2, A3
With these eliminations in place, there are now two set of Locked Candidates in box 7
* 9 must exist in column 3 because there are no other cells in column 3 where 9 is a candidate.
* 9 must be in row H, because there are no other cells in row H where 9 is a candidate.
* Therefore cell 9 is a ??????? for cell H3. (I'm looking for the term used to describe the uniqueness of digit 9 for H3)

Code: Select all

 
   1 2 3   4 5 6   7 8 9
  -----------------------
A| . . . | . . . | . . .
B| . . 6 | 4 . 5 | 1 . .
C| . 8 . | . . 1 | . 9 .
 |-------+-------+-------
D| . . 4 | . 1 . | 6 . .
E| . 7 . | . 9 . | . 2 .
F| . . 5 | . 8 . | 3 . .
 |-------+-------+-------
G| . 2 . | . . . | . 7 .
H| . . X | 6 . 3 | 5 . .
I| . . . | . . . | . . .


My question is WHAT NAME IS GIVEN TO THIS SINGLE CANDIDATE (marked X above) which must now occupy H3? Is it just a variation of a Hidden Single, or is there another name for this? I've see the same situation where there are two pointing pairs in a single box as well, where one of the cells is shared by both pointing pairs, so therefore MUST be the target cell for that digit.

TIA

[Cenoman]

Hi RedNectar,
Welcome to this forum.
Noticing the coordinates you are using, as well as the naming (pointing pairs), I suppose you are already familiar with Andrew Stuart's site sudokuwiki.org ?
In your puzzle, running the basic techniques, after spotting (79)DF9 and (89)A46 Hidden pairs in col 9 and row A resp., then you spot the pointing pairs (9)DF9 and (9)A46. Now (9)H123 and (9)GHI3 are locked in their mini-line or mini-column, each eliminating all 9's other than its own from box 7, creating a hidden single +9H3, in row H or col 3, whichever locked set you choose first (basic technique named Box-Line Reduction in Andrew's solver)

When you write

9 must exist in column 3 because there are no other cells in column 3 where 9 is a candidate.

you eliminate (BLR) 9H1 and 9H2, making 9H3 a Hidden Single in row H. End of the story, the single eliminates all remaining 9's in box 7.

[shye]

i've been casually calling this pattern a firework single, but i'd rather that didn't catch on its just similar in how it works