## example from sudoku technique web site (using hidden subset)

Post the puzzle or solving technique that's causing you trouble and someone will help

### example from sudoku technique web site (using hidden subset)

i am a newbie...cant use hidden subset much...here is wt i come out
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`----------------------------------------------------------------------------|   21     4        87521  |  6      9   7532       |  8752   7532   832 ||   9      8753   8752    |  4    532  7532       |    6       7532     1   ||   6      753     752      |  1      8       7532    |   7542     9      432  |----------------------------------------------------------------------------|   21    8761    87621  |   9      4        8652  |    3      6521   862  ||   5      9        8621     |  32    6321    8632  |    82      4         7   ||   4     8761     3         |    7    6521    8652  |    9      6521   862  |----------------------------------------------------------------------------|   8        2         65      |   53      7          4     |    1      63       9   ||   3        1          4       |    8      62         9     |   72     762     5   ||   7        65        9       |   532    6532     1     |   42      8     4326 |------------------------------------------------------------------------------`

anyone show me how to use hidden subset here?
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Last edited by spirit_fantasy on Thu Mar 30, 2006 5:25 am, edited 5 times in total.
spirit_fantasy

Posts: 12
Joined: 29 March 2006

There is a hidden pair 15 in column 8, rows 4 and 6. You can see that both 1 and 5 cannot go elsewhere in this column, so you can eliminate 26 from r4c8 and r6c8.
But forget this puzzle, it has multiple solutions (when i copied it right).
You can edit your post, mark the candidate grid and click on the "Code" button to get it better formatted.
ravel

Posts: 998
Joined: 21 February 2006

thx for showing column 8... after remain 1,5 in the cell, i can eliminate 5 from column 8, row 1 and 2 too...but wt's the next step to solve it then?
spirit_fantasy

Posts: 12
Joined: 29 March 2006

Ah, better to see now. To get to the hidden pair, you have to make a box elimination first. There are 2 ways in this case:
1. In box 6 the 5 can only go to column 8, therefore you can eliminate 5 from column 8 in boxes 3 (r1c8, r2c8) and 9 (no occurrence).
2. In column 7 the 5 can only go to box 3. So you can eliminate it from the other columns of box 3.

There are 2 more possible box/line eliminations (look at the 6 in box 8 and the 8 in box 3)

But anyway, the puzzle has more than one solutions (either it is a shame or you did not copy it correctly).

See here for better explanations of the techniques:
http://www.angusj.com/sudoku/hints.php
http://www.simes.clara.co.uk/programs/sudokutechniques.htm
ravel

Posts: 998
Joined: 21 February 2006

Hm, i saw now that you have it from Simes' site. This is the correct puzzle, you missed the 1 in row 6:
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`------------.4.|6..|...9..|4..|6.16..|.8.|.9.------------...|.4.|3..59.|...|.47..3|.1.|...------------.2.|.7.|..93.4|..9|..5...|..1|.8.------------`

But it is not the best example for hidden subsets, because you can solve it with box eliminations only.
Look at column 6 to find a hidden pair.
ravel

Posts: 998
Joined: 21 February 2006

so would you show me a puzzle that is a good example of using hidden subsets?
spirit_fantasy

Posts: 12
Joined: 29 March 2006

This puzzle from The "Almost Lost" thread is pure fun. You can find 4 hidden pairs in it (but only need 2 of them).
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`Puzzle formerly known as #024 (Red Ed) . . . | . . . | . 8 .  9 8 . | . . 7 | 3 6 .  . 7 . | . . 9 | . . . -------+-------+------ . 5 1 | . 6 . | . . .  . . . | 8 . 1 | . . .  . . . | . 9 . | 8 3 . -------+-------+------ . . . | 6 . . | . 2 .  . 9 5 | 2 . . | . 1 6  . 1 . | . . . | . . . `
ravel

Posts: 998
Joined: 21 February 2006