The New Sudoku Players' Forum

[Pilgrim5]

Did I miss something on this one? This was rated only 3 stars in the May 15, 2006 USA Today (http://puzzles.usatoday.com/sudoku/archive/2006/05/15/).

Code: Select all

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


Here's where I got stuck:

Code: Select all

5   7   4   | 3 2 6 | 8   1  9
12  136 126 | 8 9 5 | 23  7  4
289 38  29  | 4 7 1 | 235 56 36
------------+-------+----------
3   2   8   | 5 6 7 | 9   4  1
17  5   17  | 9 3 4 | 6   2  8
49  46  69  | 2 1 8 | 7   3  5
------------+-------+----------
147 14  157 | 6 8 3 | 15  9  2
128 18  125 | 7 4 9 | 135 56 36
6   9   3   | 1 5 2 | 4   8  7


The 3 star puzzles usually take about 10 minutes. What am I missing here? Thanks

[Carcul]

Hi Pilgrim5.

Welcome to this forum.

What am I missing here?

The puzzle requires advanced techniques. Here is a possible solution:

Code: Select all

 *--------------------------------------------------*
 | 5    7    4    | 3    2    6    | 8    1    9    |
 | 12   136  126  | 8    9    5    | 23   7    4    |
 | 289  38   29   | 4    7    1    | 235  56   36   |
 |----------------+----------------+----------------|
 | 3    2    8    | 5    6    7    | 9    4    1    |
 | 17   5    17   | 9    3    4    | 6    2    8    |
 | 49   46   69   | 2    1    8    | 7    3    5    |
 |----------------+----------------+----------------|
 | 147  14   157  | 6    8    3    | 15   9    2    |
 | 128  18   125  | 7    4    9    | 135  56   36   |
 | 6    9    3    | 1    5    2    | 4    8    7    |
 *--------------------------------------------------*


[r8c3]=5=[r7c3]-5-[r7c7]-1-[r8c7]=(Almost Unique Pattern: r38c789)=1|2=[r3c7]-2-[r3c3]-9-[r6c3]-6-[r6c2]-4-[r7c2](-1-[r8c3])-1-[r8c12]-2-[r8c3],

which implies r8c3<>1,2 => r8c3=5 and the puzzle is solved. You may find this post helpful.

Regards, Carcul

[Carcul]

Here is another nice loop (refer to the grid above):

[r8c1]=2=[r8c3]-2-[r3c3]-9-[r6c3]-6-[r6c2]-4-[r7c2]-1-[r8c2]-8-[r8c1],

which implies r8c1<>8 and the puzzle is solved.

Carcul

[Pilgrim5]

Thanks for the hospitality.

I'm glad I didn't miss anything obvious. I guess the 3 stars in the paper was a little understated.

I tried loops, but I need more practice on the weak inference nice loops. I appreciate the link to the guide.

Since my post, I also noted an XYZ-wing at r7c1 (17-147-14) meaning that r8c1 <> 1. Then an XY wing at r8c1 (12-28-18) meaning that r2c2 <> 1. Then an X wing with the 1s in rows 2; and 5. Then finally another XYZ-wing at r3c1 (29-289-28) meaning that r2c1 <>2 and r2c1 = 1.

These are probably related somehow to the loops you found.