The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |...|..5|...|
 |...|.1.|8..|
 |...|.48|193|
 |---+---+---|
 |.1.|4.6|.3.|
 |...|...|.67|
 |..2|.8.|...|
 |---+---+---|
 |9..|.3.|.8.|
 |5.6|...|..1|
 |..1|.5.|4..|
 *-----------*


Play/Print this puzzle online

[Leren]

Code: Select all

*--------------------------------------------------------------*
| 1     389   38     | 39    6     5      | 7     4     2      |
| 234  c379   34     |d379-2 1     37     | 8     5     6      |
| 26   b67    5      |a27    4     8      | 1     9     3      |
|--------------------+--------------------+--------------------|
| 7     1     9      | 4     2     6      | 5     3     8      |
| 348   358   348    | 35    9     1      | 2     6     7      |
| 36    356   2      | 357   8     37     | 9     1     4      |
|--------------------+--------------------+--------------------|
| 9     2     7      | 1     3     4      | 6     8     5      |
| 5     4     6      | 8     7     9      | 3     2     1      |
| 38    38    1      | 6     5     2      | 4     7     9      |
*--------------------------------------------------------------*

H2 Wing: (2=7) r3c4 - r3c2 = (7-9) r2c2 = (9) r2c4 => - 2 r2c4; stte

Leren

[pjb]

Code: Select all

 1       389     38     | 39     6      5      | 7      4      2     
b234     379    b34     | 379-2  1     b37     | 8      5      6     
 6-2     67      5      |a27     4      8      | 1      9      3     
------------------------+----------------------+---------------------
 7       1       9      | 4      2      6      | 5      3      8     
 348     358     348    | 35     9      1      | 2      6      7     
 36      356     2      | 357    8      37     | 9      1      4     
------------------------+----------------------+---------------------
 9       2       7      | 1      3      4      | 6      8      5     
 5       4       6      | 8      7      9      | 3      2      1     
 38      38      1      | 6      5      2      | 4      7      9     


(2=7)r3c4 - (7=234)r2c136 => -2 r2c4, r3c1; stte

Phil

[bat999]

Code: Select all

.-----------------.----------------.---------.
|   1    389  38  |  39    6   5   | 7  4  2 |
|   234  379  34  |  2379  1  X3-7 | 8  5  6 |
|  *26   67   5   | *27    4   8   | 1  9  3 |
:-----------------+----------------+---------:
|   7    1    9   |  4     2   6   | 5  3  8 |
|   348  358  348 |  35    9   1   | 2  6  7 |
|  B36   356  2   |  357   8  A37  | 9  1  4 |
:-----------------+----------------+---------:
|   9    2    7   |  1     3   4   | 6  8  5 |
|   5    4    6   |  8     7   9   | 3  2  1 |
|   38   38   1   |  6     5   2   | 4  7  9 |
'-----------------'----------------'---------'

A=r6c6, B=r6c1, X=r2c6
A<>3: r6c6=7->r2c6=3
B<>3: r6c1=6->r3c1=2->r3c4=7->r2c6=3
=>r2c6=3
=> - 7 r2c6; stte

[SteveG48]

Code: Select all

 *-----------------------------------------------------------*
 | 1     389   38    | 39    6     5     | 7     4     2     |
 |b234   379  b34    | 2379  1    b37    | 8     5     6     |
 |a26   a67    5     | 2-7   4     8     | 1     9     3     |
 *-------------------+-------------------+-------------------|
 | 7     1     9     | 4     2     6     | 5     3     8     |
 | 348   358   348   | 35    9     1     | 2     6     7     |
 | 36    356   2     | 357   8     37    | 9     1     4     |
 *-------------------+-------------------+-------------------|
 | 9     2     7     | 1     3     4     | 6     8     5     |
 | 5     4     6     | 8     7     9     | 3     2     1     |
 | 38    38    1     | 6     5     2     | 4     7     9     |
 *-----------------------------------------------------------*


(7=26)r3c12 - (2=347)r2c136 => -7 r3c4 ; stte

Hmm. Looks like Phil's in reverse.

[gurth]

[SteveG48]

Bat's own solution to this puzzle can be written as (3)r2c6 = (7) r3c4 => -7 r2c6 using the same logic.

Edit: Typos corrected- Thanks, Gurth!

[gurth]

Bat's own solution to this puzzle can be written as (3)r2c6 = (7) r3c4 => -7 r2c6 using the same logic.

Yes, indeed, making a shorter solution (your typos corrected in this quote)

[bat999]

...Bat's own solution to this puzzle can be written as (3)r2c6 = (7) r3c4 => -7 r2c6...

Yes, I see it.
r2c6 has two states, even if it had more than two candidates.
Either r2c6=3 or r2c6<>3.
If r2c6=3 then r2c6<>7
If r2c6<>3 then r3c4=7 (because of the strong link "equals" sign [(3)r2c6 = (7) r3c4])...
..which would zap the 7 in r2c6.

And gurth's solution toggles r6c1(36).
If it's a 3 it kills the 3 in r6c6.
If it's a 6 it kills the 3 in r6c6 through the chain.

In this puzzle I could have toggled one of those two squares with candidate 6 in column 1 and tested the results for sameness in r2c6.

I feel more confident when testing two 'nots' in the same house.
I'm not trying to say it's a better method, just my personal preference.

[gurth]

...Bat's own solution to this puzzle can be written as (3)r2c6 = (7) r3c4 => -7 r2c6...

Yes, I see it.
r2c6 has two states, even if it had more than two candidates.
Either r2c6=3 or r2c6<>3.
If r2c6=3 then r2c6<>7
If r2c6<>3 then r3c4=7 (because of the strong link "equals" sign [(3)r2c6 = (7) r3c4])...
..which would zap the 7 in r2c6.



I feel more confident when testing two 'nots' in the same house.
I'm not trying to say it's a better method, just my personal preference.

Bat, I think you still do not see it. Maybe your reasoning is correct, but it is so complicated that no wonder you couldn't see it for so long.
There is a much simpler way to understand the situation, and once you see it you will like it a bit better I think. Maybe this truth is just too simple for you to see, you are determined already that it must be hard, so you are looking for a hard explanation!

Please consider this statement afresh:
"Bat's own solution to this puzzle can be written as (3)r2c6 = (7) r3c4 => -7 r2c6 using the same logic."
Let's suppose you accept the part "(3)r2c6 = (7) r3c4" (with "=" meaning "OR") - presumably you have established that.
Now forget about the chain and the reasons WHY this "OR" relationship is true; just remember it means both sides of the "=" side cannot be false. But putting a 7 at r2c6 kills both sides! It kills the 3 at r2c6 and it kills the 7 at r3c4 because it sees that 7. So there can't be a 7 at r2c6.
Do you see this now?

[bat999]

... it means both sides of the "=" side cannot be false. But putting a 7 at r2c6 kills both sides! It kills the 3 at r2c6 and it kills the 7 at r3c4 because it sees that 7. So there can't be a 7 at r2c6.
Do you see this now?

No, not really.
But thanks for trying.
Let's move on.

[SteveG48]

I like Gurth's explanation, but Bat's way of looking at it is quite valid as well.