Stuck - Need help on next move and why?

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Stuck - Need help on next move and why?

Postby skipper » Fri May 26, 2006 5:52 am

5 X 2 X X 1 X 6 X
X X X 9 X 6 1 5 X
9 6 1 5 X X X 3 X
8 2 9 7 5 4 3 1 6
X 1 X 6 8 X X X 5
6 5 X X 1 9 8 X X
2 9 5 X 6 X 4 X 1
4 7 8 1 X 5 6 X 3
1 3 6 X X X 5 X X
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Postby emm » Fri May 26, 2006 6:08 am

Hi

Here's your grid laid out in all it's glory with the assistance of Simple Sudoku

If you download this programme it will do the donkey work for you and leave you free to fly.

Code: Select all
*-----------------------------------------------------------*
 | 5     48    2     | 348   347   1     | 79    6     4789  |
 | 37    48    347   | 9     2347  6     | 1     5     2478  |
 | 9     6     1     | 5     247   278   | 27    3     2478  |
 |-------------------+-------------------+-------------------|
 | 8     2     9     | 7     5     4     | 3     1     6     |
 | 37    1     347   | 6     8     23    | 279   2479  5     |
 | 6     5     347   | 23    1     9     | 8     247   247   |
 |-------------------+-------------------+-------------------|
 | 2     9     5     | 38    6     378   | 4     78    1     |
 | 4     7     8     | 1     29    5     | 6     29    3     |
 | 1     3     6     | 248   2479  278   | 5     2789  2789  |
 *-----------------------------------------------------------*


Now you can easily see the naked pair in box 1.
Use that and you will find another in row 2.
Now look for a hidden single in column 5.
Now you're on your own, baby ...:D
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re: Stuck - Need help on next move and why?

Postby Pat » Fri May 26, 2006 7:17 am

skipper wrote:
Code: Select all
 5 . 2 | . . 1 | . 6 .
 . . . | 9 . 6 | 1 5 .
 9 6 1 | 5 . . | . 3 .
-------+-------+------
 8 2 9 | 7 5 4 | 3 1 6
 . 1 . | 6 8 . | . . 5
 6 5 . | . 1 9 | 8 . .
-------+-------+------
 2 9 5 | . 6 . | 4 . 1
 4 7 8 | 1 . 5 | 6 . 3
 1 3 6 | . . . | 5 . .

the 3 for box1 must be in r2; so, no other 3 in that row!
now the 3 for c5 has only one possible cell (not in r2).

( box-line interaction - or angusj calls it "Locked Candidates" )
Last edited by Pat on Fri May 26, 2006 3:28 am, edited 1 time in total.
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Postby RW » Fri May 26, 2006 7:27 am

Code: Select all
 5 . 2 | . . 1 | . 6 .
 . . . | 9 . 6 | 1 5 .
 9 6 1 | 5 . . | . 3 .
-------+-------+------
 8 2 9 | 7 5 4 | 3 1 6
 . 1 . | 6 8 . | . . 5
 6 5 . | . 1 9 | 8 . .
-------+-------+------
 2 9 5 | . 6 . | 4 . 1
 4 7 8 | 1 . 5 | 6 . 3
 1 3 6 | . . . | 5 . .


3 and 7 in box 1 must be in r2c13. In box 4 there is only three empty cells. 3 and 7 has to go in different columns, otherwise there would be no availabe candidates for r2c3. 3 and 7 cannot occupy the two cells in row 5 (UR). Therefore 3 and 7 has to go in r5c1 and r6c3, leaving r5c3=4.

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Postby skipper » Fri May 26, 2006 7:27 am

Sorry emm, I am not that advanced. I can see 48 48 in box 1, and 37 37 in row 2, but what principle do i use to find the hidden single in column 5?
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Postby emm » Fri May 26, 2006 7:54 am

The pair in row 2 eliminates the 3s and 7s from the rest of row 2, right.

Now look at what you have left.

A hidden single = the only possible place for a number in a group - hidden because it's in amongst others.

There's only one .....
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Postby ravel » Fri May 26, 2006 11:38 am

RW wrote:3 and 7 in box 1 must be in r2c13. In box 4 there is only three empty cells. 3 and 7 has to go in different columns, otherwise there would be no availabe candidates for r2c3. 3 and 7 cannot occupy the two cells in row 5 (UR). Therefore 3 and 7 has to go in r5c1 and r6c3, leaving r5c3=4.

Nice, probably easier to spot without pm's than the box/line interaction + single:)
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Postby tarek » Fri May 26, 2006 1:07 pm

This puzzle will only require box-line interactions & singles to solve, The use of doubles will cut corners at the price of increasing difficulty of technique......

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