I think you are slipping. At any rate, while hard, I wouldn't consider this one a nightmare. I think that this means that I know something your program doesn't, (yet) and I think I know what it is, too.
Allow me to pull up the soapbox:
So: first you do the obvious stuff and get to here:
Code: Select all
129 6 5 |4 19 8 |7 3 129
4 92 132 |2369 7 12369 |8 29 5
12397 279 8 |239 5 1239 |4 6 129
----------------------------------------------------------------------
6 8 132 |57 139 57 |23 4 293
57 57 9 |2 6 4 |1 2398 2398
123 4 123 |8 139 1239 |6 5 7
----------------------------------------------------------------------
2589 1 6 |3579 4 39 |235 2789 238
259 259 7 |35679 8 369 |253 1 4
85 3 4 |1 2 57 |9 78 6
columns 4 and 6, which forces the 4 for column 7. State
shown after placing the 4s.
Then after solving for a bit ... you get to ...
Code: Select all
19 6 5 |4 19 8 |7 3 2
4 2 13 |36 7 137 |8 9 5
397 97 8 |39 5 2 |4 6 1
----------------------------------------------------------------------
6 8 13 |5 13 7 |2 4 9
57 57 9 |2 6 4 |1 8 3
123 4 123 |8 139 139 |6 5 7
----------------------------------------------------------------------
59 1 6 |7 4 39 |53 2 8
259 259 7 |369 8 369 |53 1 4
8 3 4 |1 2 5 |9 7 6
Then this all falls out nicely.
So what did your program have to do to solve this? Something
harder I would bet.
Thank you very much for the Daily Sudoku Nightmare, and this
forum to discuss things like this. I hope I did not make any
transcription errors writing this posting. If I did, let me know
and I will fix them.
Thanks very much again,
Laura Creighton