The New Sudoku Players' Forum

[Kent]

i would like to ask in the puzle below(ignoring all numbers except r9c5,r9c6,r1c5 and r1c6), can i safely exclude 2 from r9c5 and r9c6?? If i were to put in the number 2 in any of these two squares, then there'll be 2 solution(if r9c5=2, then r1c5 would be 3 and if r9c6=2,then r1c6 would be3) therefore there's 2 soultion and it's invalid. I need some comment on this.I'm not sure my understanding is right or wrong.Thanks

| 4 5 1 | 7 23* 23* | 6 59 8 |
| 3 7 58 | 89 6 4 | 1 59 2 |
| 9 58 6 | 1 28 25 | 7 4 3 |
+----------------+----------------+----------------+
| 2 45 3 | 49 59 6 | 8 7 1 |
| 1 46 58 | 48 7 25 | 3 26 9 |
| 7 68 9 | 3 285 15 | 58 26 4 |
+----------------+----------------+----------------+
| 8 9 4 |6 39 78 | 2 1 5 |
| 6 3 2 |5 18 98 l 4 89 7 |
| 5 2 7 |1 23* 236* | 9 3 6 |
+----------------+----------------+----------------+

[vidarino]

i would like to ask in the puzle below(ignoring all numbers except r9c5,r9c6,r1c5 and r1c6), can i safely exclude 2 from r9c5 and r9c6??

Eh, you have a solved 3 in R9C8, so several of your cells can be solved already.

But that aside, your rectangle also fits the type 1 Unique Rectangle description; Extra candidates in just one cell means that one of those extras must be true, so you can eliminate both 2 and 3 from R9C6.

Vidar

[MCC]

Kent have you made a mistake in posting the grid, as there are no 8's or 4's in row 9?

MCC

[tso]

First, as mentioned, your grid as posted is not solvable.

Second, setting that aside and focusing on the four cells you asked about:

Code: Select all

 *-----------------------------------------------------------*
 | .     .     .     | .     23    23    | .     .     .     |
 | .     .     .     | .     .     .     | .     .     .     |
 | .     .     .     | .     .     .     | .     .     .     |
 |-------------------+-------------------+-------------------|
 | .     .     .     | .     .     .     | .     .     .     |
 | .     .     .     | .     .     .     | .     .     .     |
 | .     .     .     | .     .     .     | .     .     .     |
 |-------------------+-------------------+-------------------|
 | .     .     .     | .     .     .     | .     .     .     |
 | .     .     .     | .     .     .     | .     .     .     |
 | .     .     .     | .     23    236   | .     .     .     |
 *-----------------------------------------------------------*

This is a standard Type-1 Unique Rectangle. It shows that r9c6 must be 6, nothing else. r9c5 and the other two cells can still be either 2 or 3.

[Kent]

MCc i said i exclude everything except those 4 squares.The rest of the numbers are not valid.Thanks