Karyobin wrote:Quick! Get back on topic!!
thanks for pointing out the 1,8,9 trio
but the 2,7 duo already existed all along,
there are only 2 cells available for them in r8
- Pat
Smart3 wrote:Now as most everybody knows if the guessing factor is used then LOGIC IS NOT.
em wrote:Relating this to the original question - are you saying that the number of visible candidates can determine the difference between logic and guess?
em wrote:Relating this to the original question - are you saying that the number of visible candidates can determine the difference between logic and guess?
CathyW wrote:Evidently the rest of us have a different view on what is logical to Smart3 - I wonder why he hasn't replied?
CathyW wrote:I think a lot depends on whether you are a candidate eliminator having put in all possibilities or a candidate inputter.
. 4 8 | . . 1 | 5 . .
5 . . | 7 . . | 2 . .
. 7 . | . 9 . | 6 . .
-------+-------+------
. . . | . 7 . | . . 9
. . . | 8 . 3 | . . .
8 . . | . 1 . | . . .
-------+-------+------
. . 1 | . 5 . | . 2 .
. . 2 | . . 8 | . . 6
. . 9 | 6 . . | 1 7 .
. 4 . | . . . | . . .
3 . 9 | . . 5 | . . .
. 8 . | . . 9 | . 1 6
-------+-------+------
. . 4 | . . 7 | . 9 .
2 . . | . . . | . . 7
. 9 . | 6 . . | 8 . .
-------+-------+------
7 3 . | 9 . . | . 5 .
. . . | 8 . . | 2 . 3
. . . | . . . | . 8 .
tso wrote:...and considered any entering of information into the grid as equivalent to guessing...
Though this puzzle is rated only HARD by Pappocom -- a level that it seems Wayne has implied to be solvable without pencilmarks -- this one seems beyond most solver's pen-only capabilities -- certainly mine.
* A set of 2 squares can be constrained. R8C1 and R8C2 share possibilities <27>. No other squares in row 8 have those possibilities. Thus, any additional possibilities they have can be eliminated.
R8C1 - removing <89> from <2789> leaving <27>.
R8C2 - removing <18> from <1278> leaving <27>.
Deduction pass 2; 34 squares solved; 47 remaining.
* 2 squares in block 7 form a simple locked pair. R8C1 and R8C2 share possibilities <27>. Thus, these possibilities can be removed from the rest of the block.
R7C1 - removing <7> from <36789> leaving <3689>.
R7C2 - removing <7> from <1578> leaving <158>.
Deduction pass 3; 34 squares solved; 47 remaining.
Deduction completed...
Deduction pass 1; 34 squares solved; 47 remaining.
* Intersection of row 2 with block 2. The value <4> only appears in one or more of squares R2C4, R2C5 and R2C6 of row 2. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain this value.
R3C4 - removing <4> from <478> leaving <78>.
Deduction pass 2; 34 squares solved; 47 remaining.
* Intersection of row 2 with block 3. The values <19> only appears in one or more of squares R2C7, R2C8 and R2C9 of row 2. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain these values.
R3C7 - removing <1> from <1237> leaving <237>.
R3C8 - removing <1> from <13678> leaving <3678>.
Deduction pass 3; 34 squares solved; 47 remaining.
* A set of 2 squares can be constrained. R2C7 and R7C7 share possibilities <19>. No other squares in column 7 have those possibilities. Thus, any additional possibilities they have can be eliminated.
R2C7 - removing <7> from <179> leaving <19>.
R7C7 - removing <7> from <179> leaving <19>.
Deduction pass 4; 34 squares solved; 47 remaining.
* Intersection of row 8 with block 8. The value <8> only appears in one or more of squares R8C4, R8C5 and R8C6 of row 8. These squares are the ones that intersect with block 8. Thus, the other (non-intersecting) squares of block 8 cannot contain this value.
R7C5 - removing <8> from <3489> leaving <349>.
R7C6 - removing <8> from <1348> leaving <134>.
Deduction pass 5; 34 squares solved; 47 remaining.
* Intersection of column 4 with block 5. The value <4> only appears in one or more of squares R4C4, R5C4 and R6C4 of column 4. These squares are the ones that intersect with block 5. Thus, the other (non-intersecting) squares of block 5 cannot contain this value.
R4C5 - removing <4> from <2348> leaving <238>.
R4C6 - removing <4> from <34578> leaving <3578>.
R5C5 - removing <4> from <248> leaving <28>.
R5C6 - removing <4> from <1478> leaving <178>.
Deduction pass 6; 34 squares solved; 47 remaining.
* Intersection of column 7 with block 3. The value <7> only appears in one or more of squares R1C7, R2C7 and R3C7 of column 7. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.
R2C8 - removing <7> from <178> leaving <18>.
R2C9 - removing <7> from <789> leaving <89>.
R3C8 - removing <7> from <3678> leaving <368>.
R3C9 - removing <7> from <2678> leaving <268>.
Deduction pass 7; 34 squares solved; 47 remaining.
* R2C6 is the only square in row 2 that can be a <7>. It is thus pinned to that value.