*-----------*
|532|168|794|
|497|352|186|
|186|974|532|
|---+---+---|
|975|216|843|
|843|795|621|
|261|483|975|
|---+---+---|
|359|821|467|
|628|547|319|
|714|639|258|
*-----------*
The first horizontal "three numbers units" (TNU's) are <532>, <168> and <794>, the first vertical TNU's are <541>, <982> and <367>. Since in no grid there are two identical TNU's you can easily deduct from the solved TNU's in your grid which of the candidates are not possible. Example:
- Code: Select all
*-----------------------------------------------------------*
| 2 1 9 | 8 27 5 | 6 4 3 |
| 8 7 6 | 1 4 3 | 2 9 5 |
| 25 4 3 | 6 2 9 | 1 8 7 |
|-------------------+-------------------+-------------------|
| 4567 56 45 | 3 1 46 | 9 2 8 |
| 456 3 2 | 45 9 468 | 7 1 46 |
| 1 9 48 | 7 68 2 | 5 3 46 |
|-------------------+-------------------+-------------------|
| 459 25 145 | 2459 3 7 | 8 6 129 |
| 3 256 7 | 259 568 68 | 4 5 129 |
| 4569 8 45 | 2459 56 1 | 3 57 29 |
*-----------------------------------------------------------*
As you see in C9R123 there is a TNU <357>, and in R8C123 you have a <3?7> combination. That means R8C2 <> 5.
Best wishes from Berlin
Neunmalneun
