The New Sudoku Players' Forum

[rds2301]

I meant the impossible 7 was in r7c7, the 7 in r7c1 is forced by r8c6

[tarek]

[Deleted - as this post doesn't serve any purpose now]

[tarek]

modifying the grid posted by tso, here is how the solver reached the conflict

Code: Select all

-----------------------------------------------------------------*
| .      7      .     | 7  .   7  .  -7 .   | .      .      .     |
| .      .      .     | .      .      .     | .     +7      .     |
| .      7      .     | 7  .   .     -7     | .      .      .     |
|---------------------+---------------------+---------------------|
| .      .      .     | .      .     -7     | .      .     -7     |
| .      .     +7     | .      .      .     | .      .      .     |
| .      .      .     | -7  .   -7    .     |+7      .      .     |
|---------------------+---------------------+---------------------|
|+7      .      .     | .      .      .     |-7  .   .     -7     |
|-7      .      .     |-7  .  -7    +[7]    | .      .     -7     |
| .      .      .     |-7     -7      .     | .      .     +7     |
*-----------------------------------------------------------------*


Note that all 7s in box 5 are excluded & hence the conflict

[rds2301]

tried the 1 in r9c8 simple guess leads to contradiction, what is contradictory about r1c2, r2c2 and r7c1 and r8c1 all having a 1

[tarek]

tried the 1 in r9c8 simple guess leads to contradiction, what is contradictory about r1c2, r2c2 and r7c1 and r8c1 all having a 1

Simple guess would imply that if r9c8 would be 1, then single (naked/hidden) eliminations from there would lead eventually to a conflict (it doesn't have to be in 1s).

tarek

[tso]

Tarek was correct -- all four Nishios are valid. Sorry for the confusion caused by my inaccurate post.