The New Sudoku Players' Forum

[eniacap]

I entered this puzzle into "Sudoku Solver" because i could solve it only with a guess, and wanted to see if logic could succeed. It reached this point where a swordfish pattern was found:-

Code: Select all

 ...1...|...2...|..489..|...3...|.4689..|...7...|...68..|...5...|...49..|
 ...6...|*.4789.|..4789.|*.249..|.2489..|...5...|..1278.|*.1278.|...3...|
 ..347..|...5...|.34789.|...1...|.24689.|..289..|..2678.|..2678.|...49..|
--------|-------|-------|-------|-------|-------|-------|-------|-------|
 ...9...|...47..|...5...|...24..|...78..|...1...|..248..|...3...|...6...|
 ..2347.|..347..|.12347.|...6...|..789..|...89..|.12458.|..128..|...15..|
 ...8...|...6...|..124..|...5...|..234..|...23..|...9...|...12..|...7...|
--------|-------|-------|-------|-------|-------|-------|-------|-------|
 ..237..|*.3789.|236789.|*..29..|.12359.|...4...|.13567.|*.1679.|..15...|
 ...5...|*.3479.|.34679.|*..8...|..139..|...39..|..1367.|*.1679.|...2...|
 ...23..|...1...|..239..|...7...|..2359.|...6...|...35..|...4...|...8...|
--------|-------|-------|-------|-------|-------|-------|-------|-------|

I can see that columns 4 and 8 have pairs of cells where 9 must be in one or the other, but the others (rows B,G,H and column 2) don't seem to follow the pattern. There are 9s galore in these. Can someone please expain?

[RW]

Code: Select all

 *-----------------------------------------------------------------------------*
 | 1       2       489     | 3       4689    7       | 68      5       49      |
 | 6      *4789   -4789    |*249    -2489    5       | 1278    1278    3       |
 | 347     5       34789   | 1       24689   289     | 2678    2678    49      |
 |-------------------------+-------------------------+-------------------------|
 | 9       47      5       | 24      78      1       | 248     3       6       |
 | 2347    347     12347   | 6       789     89      | 12458   128     15      |
 | 8       6       124     | 5       234     23      | 9       12      7       |
 |-------------------------+-------------------------+-------------------------|
 | 237    *3789   -236789  |*29     -12359   4       | 13567  *1679    15      |
 | 5      *3479   -34679   | 8      -139    -39      | 1367   *1679    2       |
 | 23      1       239     | 7       2359    6       | 35      4       8       |
 *-----------------------------------------------------------------------------*

Columns 2, 4 and 8 have candidate 9 only in rows 2, 7 and 8. What happens if digit 9 goes in any other column in one of those rows?

RW