The New Sudoku Players' Forum

[oliverliu2]

Somebody help me!!!!

What's the next?????

Code: Select all

   2 7   
2       5
 64  521
 1 5 296
9       2
 2 4 9 8
 83 2 75
5       9
   356   


Thanks

[NorwegianViking]

Hello

Have you tried to write down all the candidates for each cell?

There is one Hidden Single:

In Block 8 (or Row 7) there is a 9 (In R7C4)

[oliverliu2]

Not yet.
But how do you know the R7C4 is 9

Thanks

[oliverliu2]

Yes. I know why the R7C4 is 9.

Thanks

[NorwegianViking]

Your puzzle:

Code: Select all

+--+--+--+--+--+--+--+--+--+
|*  *  * |2  *  7 |*  *  * |
|2  *  * |*  *  * |*  *  5 |
|*  6  4 |*  *  5 |2  1  * |
+--+--+--+--+--+--+--+--+--+
|*  1  * |5  *  2 |9  6  * |
|9  *  * |*  *  * |*  *  2 |
|*  2  * |4  *  9 |*  8  * |
+--+--+--+--+--+--+--+--+--+
|*  8  3 |*  2  * |7  5  * |
|5  *  * |*  *  * |*  *  9 |
|*  *  * |3  5  6 |*  *  * |
+--+--+--+--+--+--+--+--+--+


Possible candidates:
I didn't have to use Possible Candidates to find the 9, but it is definately the thing to do when one is stuck.
It is time consuming, but many of the advanced methodes are based on this, so there is no way around it.
Already when looking for hidden Singles it makes life a lot simpler.
I have made an Excel application to give me all the Possible Candidates, but if I do a puzzle manually, I wait as long as I can because of the tedious job of maintaining them. (And limited space in the newspapers puzzles)

This is how I spotted the 9.

Consider row 7-9

Code: Select all

   C 1  2  3  4  5  6  7  8  9
----+--+--+--+--+--+--+--+--+--+
R7  |*  8  3 |*  2  * |7  5  * |
R8  |5  *  * |*  *  * |*  *  9 |
R9  |*  *  * |3  5  6 |*  *  * |
----+--+--+--+--+--+--+--+--+--+
     Block 7  Block 8  Block 9


There are three numbers in a row (row 9) inside one block (Block 8).
Then it pays to look for a fourth number on a different row (Row 7 or Row 8) in a different block (Block 7 or Block 9).
Two numbers qualify - the 8 in R7C2 (Block 7) and the 9 in R8C9 (Block 9).
It is now easy to find the rows for 8 and 9 in each block (Block 7-9).
If we look at where to place the 9 in Block 8, it has to go somewhere in row 7. Then both Row 7 and 8 has a 9, so the 9 in Block 7 has to go somewhere in Row 9. In Block 7 we can rule out R9C1, as Column 1 already has a 9. We don't get closer at this time. But in Block 7 we can pin the exact position. R7C5 is occupied, and there is a 9 in Column 6.
So the 9 has to go in R7C4.
None of the 8's can be pinned at this time, but at least we know the rows.

I suppose the rule could be formulated like this:
When three numbers on the same row inside a block:
- If a fourth number is in an adjoing block, on a different row:
Result:
- this fourth number has to be on the remaining row in the block with the three numbers.
- this fourth number has to be on the same row as the three numbers in the remaining block.

After filling in the 9:
R3C4: 8 (Naked Single)
R3C5: 9 (Hidden Single)
Then I needed to do some ellimination (Remove 8 from R8C7, R8C2 and R8C3).
From then on, it was all Naked or Hidden singles.

For reference, I include the Possible Candidates as it looked when you posted the puzzle.

Code: Select all

+-------+-------+-------+-------+-----------+-------+---------+-------+-------+
|1,3,8  |3,5,9  |1,5,8,9|2      |1,3,4,6,8,9|7      |3,4,6,8  |3,4,9  |3,4,6,8|
|2      |3,7,9  |1,7,8,9|1,6,8,9|1,3,4,6,8,9|1,3,4,8|3,4,6,8  |3,4,7,9|5      |
|3,7,8  |6      |4      |8,9    |3,8,9      |5      |2        |1      |3,7,8  |
+-------+-------+-------+-------+-----------+-------+---------+-------+-------+
|3,4,7,8|1      |7,8    |5      |3,7,8      |2      |9        |6      |3,4,7  |
|9      |3,4,5,7|5,6,7,8|1,6,7,8|1,3,6,7,8  |1,3,8  |1,3,4,5  |3,4,7  |2      |
|3,6,7  |2      |5,6,7  |4      |1,3,6,7    |9      |1,3,5    |8      |1,3,7  |
+-------+-------+-------+-------+-----------+-------+---------+-------+-------+
|1,4,6  |8      |3      |1,9    |2          |1,4    |7        |5      |1,4,6  |
|5      |4,7    |1,2,6,7|1,7,8  |1,4,7,8    |1,4,8  |1,3,4,6,8|2,3,4  |9      |
|1,4,7  |4,7,9  |1,2,7,9|3      |5          |6      |1,4,8    |2,4    |1,4,8  |
+-------+-------+-------+-------+-----------+-------+---------+-------+-------+