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MM 1398 and 1400

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat May 09, 2009 3:32 am    Post subject: MM 1398 and 1400 Reply with quote
#1398
Code:
+-------+-------+-------+
| . . . | . . 1 | . 2 . |
| . 3 . | 5 7 . | . 1 . |
| 8 6 . | . . . | . . . |
+-------+-------+-------+
| . . . | 7 8 . | . . 3 |
| 2 7 . | . . . | . 4 8 |
| 9 . . | . . 5 | 7 . . |
+-------+-------+-------+
| . . . | . . . | . 5 1 |
| . 4 . | . 1 6 | . 8 . |
| . 2 . | 4 . . | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

#1400
Code:

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

Play this puzzle online at the Daily Sudoku site

Last edited by storm_norm on Sun May 10, 2009 8:18 am; edited 2 times in total
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Sat May 09, 2009 5:36 pm    Post subject: Reply with quote
Code:
 after basics: <36> and <69> URs don't seem to help
 +--------------------------------------------------------------+
 |  57    59    579   |  368   36    1     |  38    2     4     |
 |  4     3     2     |  5     7    @89    |  689   1     69    |
 |  8     6     1     |  239   239   4     |  39    7     5     |
 |--------------------+--------------------+--------------------|
 |  6     15    4     |  7     8     2     |  15    9     3     |
 |  2     7     5-3   |  1369  369   39    |  15    4     8     |
 |  9     18   @38    |  1-3   4     5     |  7     6     2     |
 |--------------------+--------------------+--------------------|
 |  37    89    6     |  2389  239   3789  |  4     5     1     |
 |  357   4     579   |  39    1     6     |  2     8     79    |
 |  1     2    *789   |  4     5    *789   |  69    3     679   |
 +--------------------------------------------------------------+
 # 53 eliminations remain

Ignoring the 4-cell XY-Chain that cracks the puzzle, there's a chain segment created by the strong link in [r9] on <8> and bivalue cells containing <8> in [c3] and [c6].

Code:
 (3=8)r6c3 - r9c3 = r9c6 - (8=9)r2c6

Either [r6c3]=3 or [r2c6]=9. Now, cell [r5c6]=39 falls into play.

Code:
 (3=8)r6c3 - r9c3 = r9c6 - (8=9)r2c6 - (9=3)r5c6 => [r5c3],r6c4]<>3


{corrected typo: [r2c3] => [r2c6] }

Last edited by daj95376 on Sat May 09, 2009 11:14 pm; edited 1 time in total
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wapati



Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
PostPosted: Sat May 09, 2009 8:05 pm    Post subject: Reply with quote
I like 4-cell xy-chains.

Didn't find one here?
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sat May 09, 2009 10:26 pm    Post subject: Reply with quote
daj95376 wrote:
Code:
 after basics: <36> and <69> URs don't seem to help
 +--------------------------------------------------------------+
 |  57    59    579   |  368   36    1     |  38    2     4     |
 |  4     3     2     |  5     7    @89    |  689   1     69    |
 |  8     6     1     |  239   239   4     |  39    7     5     |
 |--------------------+--------------------+--------------------|
 |  6     15    4     |  7     8     2     |  15    9     3     |
 |  2     7     5-3   |  1369  369   39    |  15    4     8     |
 |  9     18   @38    |  1-3   4     5     |  7     6     2     |
 |--------------------+--------------------+--------------------|
 |  37    89    6     |  2389  239   3789  |  4     5     1     |
 |  357   4     579   |  39    1     6     |  2     8     79    |
 |  1     2    *789   |  4     5    *789   |  69    3     679   |
 +--------------------------------------------------------------+
 # 53 eliminations remain

Ignoring the 4-cell XY-Chain that cracks the puzzle, there's a chain segment created by the strong link in [r9] on <8> and bivalue cells containing <8> in [c3] and [c6].

Code:
 (3=8)r6c3 - r9c3 = r9c6 - (8=9)r2c3

Either [r6c3]=3 or [r2c6]=9. Now, cell [r5c6]=39 falls into play.

Code:
 (3=8)r6c3 - r9c3 = r9c6 - (8=9)r2c3 - (9=3)r5c6 => [r5c3],r6c4]<>3

I like it.
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daj95376



Joined: 23 Aug 2008
Posts: 3854
PostPosted: Sat May 09, 2009 11:10 pm    Post subject: Reply with quote
wapati wrote:
I like 4-cell xy-chains.

Didn't find one here?

My elimination in [r6c4] made it harder to spot.

Code:
 (9=8)r7c2 - (8=1)r6c2 - (1=3)r6c4 - (3=9)r8c4 => [r7c456],[r8c3]<>9


[Note: I corrected a typo in my original post.]
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Sun May 10, 2009 8:19 am    Post subject: Reply with quote
#1400 after basics
hmm, harder than 1398?
Code:
.------------------.------------------.------------------.
| 45    9     1    | 6     8     3    | 245   7     24   |
| 345   237   245  | 579   457   1    | 6     39    8    |
| 6     378   458  | 579   457   2    | 45    39    1    |
:------------------+------------------+------------------:
| 1     38    48   | 2     367   46   | 9     5     3467 |
| 9     23    245  | 578   1     456  | 478   48    3467 |
| 345   6     7    | 58    35    9    | 248   1     234  |
:------------------+------------------+------------------:
| 7     4     6    | 1     9     8    | 3     2     5    |
| 2     1     9    | 3     56    56   | 478   48    47   |
| 8     5     3    | 4     2     7    | 1     6     9    |
'------------------'------------------'------------------'
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Mon May 11, 2009 12:11 am    Post subject: Reply with quote
1400
Code:
 *-----------------------------------------------------------*
 | 45    9     1     | 6     8     3     | 245   7     24    |
 | 345  *237   245   |*579   45-7  1     | 6    *39    8     |
 | 6    *378   458   |*579   45-7  2     | 45   *39    1     |
 |-------------------+-------------------+-------------------|
 | 1     38    48    | 2     367   46    | 9     5     3467  |
 | 9     23    245   | 578   1     456   | 478   48    3467  |
 | 345   6     7     | 58    35    9     | 248   1     234   |
 |-------------------+-------------------+-------------------|
 | 7     4     6     | 1     9     8     | 3     2     5     |
 | 2     1     9     | 3     56    56    | 478   48    47    |
 | 8     5     3     | 4     2     7     | 1     6     9     |
 *-----------------------------------------------------------*
Is there a ur of 39 and 57 causing r23c5<>7?

I know just enough about ur's to get into trouble! Confused
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon May 11, 2009 1:03 am    Post subject: Reply with quote
arkietech wrote:
1400
Code:
 *-----------------------------------------------------------*
 | 45    9     1     | 6     8     3     | 245   7     24    |
 | 345  *237   245   |*579   45-7  1     | 6    *39    8     |
 | 6    *378   458   |*579   45-7  2     | 45   *39    1     |
 |-------------------+-------------------+-------------------|
 | 1     38    48    | 2     367   46    | 9     5     3467  |
 | 9     23    245   | 578   1     456   | 478   48    3467  |
 | 345   6     7     | 58    35    9     | 248   1     234   |
 |-------------------+-------------------+-------------------|
 | 7     4     6     | 1     9     8     | 3     2     5     |
 | 2     1     9     | 3     56    56    | 478   48    47    |
 | 8     5     3     | 4     2     7     | 1     6     9     |
 *-----------------------------------------------------------*
Is there a ur of 39 and 57 causing r23c5<>7?

I know just enough about ur's to get into trouble! Confused


NO.
first of all, there isn't a UR instance with {3,9}. the candidates would need to be located in more than two cells.

there is, however, a almost deadly pattern of the kind that Marty likes to find. the {3,7,9} deadly pattern is almost there across rows 2 and 3.

there is a UR instance with {4,5} in r23c34. but even this situation doesn't allow for an easy inference to be made.
I can PM you a NET that can be formed from the {4,5} UR that solves it in one fell swoop if you wish.

if you want a hint at a UR that has some inference value, take a look at the x-wing on 2's in columns 7 and 9. all four of those cells contain a 4 also. this "almost" UR on {2,4} causes an elimination in column 1.
I'll give you a hint, how many other 4's are there in the rows of the x-wing on 2?
which column are they in?

And the hidden UR in those same cells which most solvers would find easier. the {2,4} UR in r16c79 would allow the removal of 4 from r6c7 immediately.
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
PostPosted: Mon May 11, 2009 1:29 am    Post subject: Reply with quote
storm_norm wrote:

NO.
first of all, there isn't a UR instance with {3,9}. the candidates would need to be located in more than two cells.

there is, however, a almost deadly pattern of the kind that Marty likes to find. the {3,7,9} deadly pattern is almost there across rows 2 and 3.

there is a UR instance with {4,5} in r23c34. but even this situation doesn't allow for an easy inference to be made.
I can PM you a NET that can be formed from the {4,5} UR that solves it in one fell swoop if you wish.

if you want a hint at a UR that has some inference value, take a look at the x-wing on 2's in columns 7 and 9. all four of those cells contain a 4 also. this "almost" UR on {2,4} causes an elimination in column 1.
I'll give you a hint, how many other 4's are there in the rows of the x-wing on 2?
which column are they in?

And the hidden UR in those same cells which most solvers would find easier. the {2,4} UR in r16c79 would allow the removal of 4 from r6c7 immediately.

Thanks Norm. I will have to study this some.
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Kdelle



Joined: 20 Mar 2008
Posts: 59
Location: Hudson, NH
PostPosted: Mon May 11, 2009 5:18 pm    Post subject: Reply with quote
Norm,

After eliminating 4 from r2c1 and r6c7 I am still stuck. Do you have another hint? Or am I missing something obvious?

Thanks,

Kathy
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon May 11, 2009 5:54 pm    Post subject: Reply with quote
Kdelle wrote:
Norm,

After eliminating 4 from r2c1 and r6c7 I am still stuck. Do you have another hint? Or am I missing something obvious?

Thanks,

Kathy


Kathy,
nothing obvious after those eliminations. this puzzle IS a true diabolical in every sense of the word.
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