How hard is this puzzle?

Everything about Sudoku that doesn't fit in one of the other sections

Postby udosuk » Tue Feb 13, 2007 4:43 pm

ravel wrote:To be more precise, the "Strong link of 1s in r5c78 => UR-type 4" doesn't exist here.

Thanks ravel... It's my turn to be blind...:)
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Postby Carcul » Tue Feb 13, 2007 5:34 pm

Ravel wrote:If you remove the 2 in r9c1 instead, you get a harder one:


Code: Select all
 *------------------------------------------------------------*
 | 3678   5      4   | 389    2      79  | 1378   13789  3689 |
 | 3678   2      9   | 348    47     1   | 378    5      368  |
 | 378    378    1   | 389    5      6   | 4      23789  2389 |
 |-------------------+-------------------+--------------------|
 | 1      37     5   | 49     47     8   | 237    6      239  |
 | 4      678    267 | 5      3      279 | 178    1789   89   |
 | 2378   9      237 | 16     16     27  | 5      378    4    |
 |-------------------+-------------------+--------------------|
 | 59     346    236 | 126    169    45  | 368    38     7    |
 | 59     346    8   | 7      69     45  | 236    23     1    |
 | 27     1      267 | 26     8      3   | 9      4      5    |
 *------------------------------------------------------------*

1. [r3c2]=8=[r5c2]-8-[r6c1]=8=[r6c8]-8-[r7c8]-3-[r7c3]=3=[r6c3](-3-
-[r6c1])-3-[r4c2]-7-[r4c2], => r4c2<>7, r6c1<>3.

2. [r4c5]-7-[r4c2]-3-[r6c3]-2-[r6c6]-7-[r4c5], => r4c5<>7.

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Postby 999_Springs » Fri Mar 02, 2007 8:53 pm

Is it possible to remove both the 2 in r9c1 and the 1 in r4c1 and still get a puzzle with a unique solution?

(I was going to post this much earlier but due to "circumstances beyond my control" I was unable to access this site then.)
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Postby ravel » Fri Mar 02, 2007 9:47 pm

No, there are 3 minimal puzzles, without 9 in r1c6 and 2 in r9c1, without 9 in r1c6 and 9 in r9c7 and without 1 in r4c1.

I calculate them using gsf's program, where i have a batch file (i called it gsfmin.bat) with this text, entered in notepad:
sudoku -m puzzles.txt > min.txt
When i copy the puzzle(s) to puzzles.txt (in the directory of gsf's program and the batch file), i only need to doubleclick the batch file in the explorer to get the minimals in min.txt.
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Postby ArkieTech » Fri Mar 02, 2007 10:13 pm

post deleted
Last edited by ArkieTech on Sat Mar 03, 2007 12:18 am, edited 1 time in total.
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Postby ravel » Sat Mar 03, 2007 12:06 am

ArkieTech wrote:Single [R7C2]= 6
Cant see that, please explain.
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Postby daj95376 » Sat Mar 03, 2007 1:12 am

These eliminations are not supported by the contents of the grid when they occur.

Code: Select all
ColBox [R7C2]<> 6
ColBox [R8C2]<> 6

 *--------------------------------------------------------------------*
 | 3678   5      4      | 389    2      79     | 1378   13789  3689   |
 | 3678   2      9      | 348    478    1      | 378    5      368    |
 | 378    378    1      | 389    5      6      | 4      23789  2389   |
 |----------------------+----------------------+----------------------|
 | 1      37     5      | 249    479    8      | 237    6      239    |
 | 4     *678   *267    | 5      3      279    | 1278   12789  289    |
 | 2378   9      237    | 126    167    27     | 5      2378   4      |
 |----------------------+----------------------+----------------------|
 | 2359   34-6  *236    | 1269   169    2459   | 2368   238    7      |
 | 2359   34-6   8      | 7      69     2459   | 236    23     1      |
 | 27     1     *267    | 268    68     3      | 9      4      5      |
 *--------------------------------------------------------------------*
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Postby ArkieTech » Sat Mar 03, 2007 4:14 am

ravel said:
Cant see that, please explain.

daj95376 said:
These eliminations are not supported by the contents of the grid when they occur.


OOPs:( My boo boo I will delete my post.

Sorry about the confusion.

Hope this is right
Code: Select all
*-----------*
|.5.|.2.|...|
|.29|..1|.5.|
|...|..6|4..|
|---+---+---|
|1.5|..8|.6.|
|4..|53.|...|
|.9.|...|..4|
|---+---+---|
|...|...|..7|
|..8|7..|..1|
|.1.|..3|9..|
*-----------*
*--------------------------------------------------------------------------*
| 3678    5       13467  | 3489    2       479    | 13678   13789   3689   |
| 3678    2       9      | 348     478     1      | 3678    5       368    |
| 378     378     137    | 389     5789    6      | 4       123789  2389   |
|------------------------+------------------------+------------------------|
| 1       37      5      | 249     479     8      | 237     6       239    |
| 4       678     267    | 5       3       279    | 1278    12789   289    |
| 23678   9       2367   | 126     167     27     | 123578  12378   4      |
|------------------------+------------------------+------------------------|
| 23569   346     2346   | 124689  145689  2459   | 23568   2348    7      |
| 23569   346     8      | 7       4569    2459   | 2356    234     1      |
| 2567    1       2467   | 2468    4568    3      | 9       248     2568   |
*--------------------------------------------------------------------------*
Hidden Single  [R3C5]=5 Row
Hidden Single  [R6C7]=5 Row
Hidden Single  [R9C9]=5 Col
Hidden Single  [R1C3]=4 Box
Hidden Single  [R3C3]=1 Col
BoxCol [R9C1]<> 6
BoxRow [R6C8]<> 1
BoxRow [R6C3]<> 6
BoxCol [R7C1]<> 6
BoxCol [R2C7]<> 6
ColBox [R7C4]<> 4
ColBox [R9C4]<> 4
ColBox [R7C5]<> 4
ColBox [R8C5]<> 4
ColBox [R9C5]<> 4
Hidden Single  [R9C8]=4 Row
BoxCol [R7C4]<> 6
BoxCol [R2C5]<> 8
Then it takes trips
 *--------------------------------------------------------------------*
 | 3678   5      4      | 389    2      79     | 1378   13789  3689   |
 | 3678   2      9      | 348    478    1      | 378    5      368    |
 | 378    378    1      | 389    5      6      | 4      23789  2389   |
 |----------------------+----------------------+----------------------|
 | 1      37     5      | 249    479    8      | 237    6      239    |
 | 4      678    267    | 5      3      279    | 1278   12789  289    |
 | 2378   9      237    | 126    167    27     | 5      2378   4      |
 |----------------------+----------------------+----------------------|
 | 2359   346    236    | 1269   169    2459   | 2368   238    7      |
 | 2359   346    8      | 7      69     2459   | 236    23     1      |
 | 27     1      267    | 268    68     3      | 9      4      5      |
 *--------------------------------------------------------------------*
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Postby Eioru » Sat Mar 03, 2007 12:28 pm

I want to know what this puzzle rating in ER and its content. Thanks.
Code: Select all
 4 . . | 2 . . | 3 . .
 . . 7 | . . 8 | . . 4
 . 8 . | . 6 . | . 5 .
-------+-------+-------
 2 . . | . . . | 5 . .
 . . 1 | . . . | . . 7
 . 6 . | . . . | . 9 .
-------+-------+-------
 3 . . | 7 . . | . . .
 . . 8 | . . 2 | . . 3
 . 5 . | . 9 . | . 1 .
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Postby ronk » Sat Mar 03, 2007 1:13 pm

Eioru wrote:I want to know what this puzzle rating in ER and its content. Thanks.

You may download (or launch) Sudoku Explainer from here.
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