The New Sudoku Players' Forum

[Prometheus bound]

I'm running a program (Simple Sudoku) that can generate a hint if you are stuck. When I do this, I always try to understand why the action is allowed. In this case, I cannot. If anyone can explain why the 3's can be dropped from col. 2,4,9 of row 7, I'd be most appreciative...

215|.4.|..8
987|.53|.4.
643|...|.5.
-----------
1..|.78|56.
579|.1.|82.
.6.|5..|..7
-----------
...|...|47.
.9.|7..|..5
7..|.6.|982


{2} {1} {5} {69} {4} {679} {367} {39} {8}
{9} {8} {7} {126} {5} {3} {126} {4} {16}
{6} {4} {3} {1289} {289} {1279} {127} {5} {19}
{1} {23} {24} {2349} {7} {8} {5} {6} {349}
{5} {7} {9} {346} {1} {46} {8} {2} {34}
{348} {6} {248} {5} {239} {249} {13} {139} {7}
{38} {235} {1268} {12389} {2389} {1259} {4} {7} {136}
{348} {9} {12468} {7} {238} {124} {136} {13} {5}
{7} {35} {14} {134} {6} {145} {9} {8} {2}

[tso]

Press "control 3" to fliter candidate 3s.

Code: Select all

The 3 in row 4 must be in column 2 or 4 or 9.
The 3 in row 5 must be in column . . .4 or 9.
The 3 in row 9 must be in column 2 or 4.


No matter how you place the 3s in these three rows, there will be one in each column. Therefore, you may removed all other candidate 3s from those three columns.

[Prometheus bound]

Ok, I feel silly. Thanks

[cho]

Same difficulty. Can someone explain the 6 provided as a hint in r8c9?

Code: Select all

..2.568..
51..7..4.
......5..
63.249.58
.5.6.7...
2...15.64
925.6.487
.4.598.26
.4.7249.5

Thanks.

cho
edit: found it - thanks

[simes]

Cho, your grid isn't correct. Two 4s in column 2 and two 4s in row 9.

Simes

[george-no1]

For this puzzle to have a unique solution, you must get rid of the 4 at r9c2 and place an 8 at r9c3.

G

[cho]

Sorry, a bit of transpositioning there. For any interested row 9 should have been |.68|724|9.5|. George is quite correct. Figures I'd leave out the 8 that I was overlooking for an hour.

cho