Let's use this code from another topic.
.-----------------------.-----------------------.-----------------------.
|7 6 1 |8 3 2 |4 9 5 |
|4 9 8 |1 6 5 |2 37 37 |
|3 5 2 |4 9 7 |6 1 8 |
:-----------------------+-----------------------+-----------------------:
|9 38 67 |63 4 1 |378 5 2 |
|58 4 35 |2 7 9 |1 368 36 |
|2 1 67 |36 5 8 |37 4 9 |
:-----------------------+-----------------------+-----------------------:
|1 37 9 |57 8 6 |35 2 4 |
|568 2 35 |57 1 4 |9 3678 367 |
|56 78 4 |9 2 3 |58 67 1 |
'-----------------------'-----------------------'-----------------------'
Let's suppose that number 5 is in R8C1 or R9C1 (they are in line) then R5C1=8, R4C7=8, R8C7=5. Then we can eliminate 5 from R9C1.
Is this valid?
Hi Novajlija, welcome to the site.
The chain is a classic Forcing Chain, but you do not need to consider R8C1=5, just R9C1.
The grid:
This is a AIC that does the same elimination:
(5=8)r5c1-(8)r5c8=(8)r4c7-(8=5)r9c7 => r9c1<>5
It looks a bit like a W-Wing with the same pair at both ends.
Ruud
The last node in your chain should be R9C7=5.Let's suppose that number 5 is in R8C1 or R9C1 (they are in line) then R5C1=8, R4C7=8, R8C7=5. Then we can eliminate 5 from R9C1.
The chain is a classic Forcing Chain, but you do not need to consider R8C1=5, just R9C1.
The grid:
Code: Select all
.------------------.------------------.------------------.
| 7 6 1 | 8 3 2 | 4 9 5 |
| 4 9 8 | 1 6 5 | 2 37 37 |
| 3 5 2 | 4 9 7 | 6 1 8 |
:------------------+------------------+------------------:
| 9 38 67 | 36 4 1 |*378 5 2 |
|*58 4 35 | 2 7 9 | 1 *368 36 |
| 2 1 67 | 36 5 8 | 37 4 9 |
:------------------+------------------+------------------:
| 1 37 9 | 57 8 6 | 35 2 4 |
| 568 2 35 | 57 1 4 | 9 3678 367 |
|-56 78 4 | 9 2 3 |*58 67 1 |
'------------------'------------------'------------------'
(5=8)r5c1-(8)r5c8=(8)r4c7-(8=5)r9c7 => r9c1<>5
It looks a bit like a W-Wing with the same pair at both ends.
Ruud