The New Sudoku Players' Forum

[ab]

according to my solver this puzzle has one solution:

Code: Select all

...|...|...
.4.|2.1|.6.
..8|.7.|9..
-----------
.8.|...|.5.
..5|...|8..
.6.|...|.4.
-----------
..9|.8.|5..
.1.|6.4|.2.
...|...|...


but as you solve it you reach a point where R2C3=R2C7=R8C3=R8C7=(3 or 7). Now according to UR this would lead to 2 solutions. So I put the puzzle into P.J.Downey's program and it only finds one solution too. What's going on??

[gsf]

but as you solve it you reach a point where R2C3=R2C7=R8C3=R8C7=(3 or 7). Now according to UR this would lead to 2 solutions. So I put the puzzle into P.J.Downey's program and it only finds one solution too. What's going on??

can you provide a pencimark grid showing the point in question?
[edit] well duh the opening grid has it

Code: Select all

1235679  23579   12367  | 34589   34569   35689  | 12347    1378  1234578
  3579     4       37   |   2      359      1    |   37      6      3578
 12356    235      8    |  345      7      356   |   9       13    12345
------------------------+------------------------+------------------------
 123479    8     12347  | 13479   123469  23679  | 12367     5     123679
 123479   2379     5    | 13479   123469  23679  |   8      1379   123679
 12379     6      1237  | 135789  12359   235789 |  1237     4     12379
------------------------+------------------------+------------------------
 23467    237      9    |  137      8      237   |   5      137    13467
  3578     1       37   |   6      359      4    |   37      2      3789
2345678   2357   23467  | 13579   12359   23579  | 13467   13789  1346789


and it can be advanced to this point

Code: Select all

12367   9    126  | 3458   46   3568 | 124   137   1245
  5     4     37  |  2     9     1   |  37    6     8
 1236   3     8   | 345    7    356  |  9     13   1245
------------------+------------------+------------------
 1234   8    124  | 479   146   2679 | 126    5    1236
 1234   7     5   |  4    146    26  |  8     9    1236
  9     6     12  |  58    3     58  |  12    4     7
------------------+------------------+------------------
  46    2     9   |  1     8     37  |  5     37    46
  8     1     37  |  6     5     4   |  37    2     9
 3467   5     46  | 379    2    379  | 146    8    146


[re'born]

but as you solve it you reach a point where R2C3=R2C7=R8C3=R8C7=(3 or 7). Now according to UR this would lead to 2 solutions. So I put the puzzle into P.J.Downey's program and it only finds one solution too. What's going on??

The 4 cells you list do not form a unique rectangle. Unique rectangles must lie in exactly 2 rows, 2 columns and 2 blocks.