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enxio27
 Post subject: What am I missing here?
PostPosted: Tue Jul 01, 2008 1:30 pm 
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This is the lower left grid of a samurai puzzle, as far as I've solved it. I've solved all the other grids, and Sudocue says this one is valid, as well. I'm sure I've just been staring at it too long and I'm missing something easy, but I don't know what it is. Can someone clue me in?

Code:
.-------------------------------.-------------------------------.-------------------------------.
| 268       4         28        | 29        7         269       | 1         3         5         |
| 16        5         7         | 4         3         16        | 2         9         8         |
| 12        3         9         | 5         8         12        | 6         7         4         |
:-------------------------------+-------------------------------+-------------------------------:
| 2459      1         24        | 29        245       3         | 8         6         7         |
| 25        7         3         | 6         25        8         | 4         1         9         |
| 49        8         6         | 7         1         49        | 5         2         3         |
:-------------------------------+-------------------------------+-------------------------------:
| 7         6         5         | 3         24        24        | 9         8         1         |
| 48        9         48        | 1         6         7         | 3         5         2         |
| 3         2         1         | 8         9         5         | 7         4         6         |
'-------------------------------.-------------------------------.-------------------------------'



Here's the entire puzzle if you're interested:

Code:
005000000070640192900800470091720800050100964000004000024360000036070000010080000
000000700746028010095004008001047950352009070000100000000071860000080340000030090
000050000000000000000070000000587000807204305000139000000090000000000000000020000
040070000057030000039580000000003000070600419086710500700300980090160352001000000
000030050000010960000065430000700000826001070007054210018003009432079080000000600
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JLynn
PostPosted: Tue Jul 01, 2008 2:09 pm 
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Two steps, an X-Wing and an XY-wing:

X-wing:
Hidden Text:
Code:
.-------------------------------.-------------------------------.-------------------------------.
| -268       4         *28        | *29        7         -269       | 1         3         5         |
| 16        5         7         | 4         3         16        | 2         9         8         |
| 12        3         9         | 5         8         12        | 6         7         4         |
:-------------------------------+-------------------------------+-------------------------------:
| -2459      1         *24        | *29        -245       3         | 8         6         7         |
| 25        7         3         | 6         25        8         | 4         1         9         |
| 49        8         6         | 7         1         49        | 5         2         3         |
:-------------------------------+-------------------------------+-------------------------------:
| 7         6         5         | 3         24        24        | 9         8         1         |
| 48        9         48        | 1         6         7         | 3         5         2         |
| 3         2         1         | 8         9         5         | 7         4         6         |
'-------------------------------.-------------------------------.-------------------------------'



XY-Wing:
Hidden Text:
Code:
.-------------------------------.-------------------------------.-------------------------------.
| 68       4         28        | 29        7         69       | 1         3         5         |
| 16        5         7         | 4         3         16        | 2         9         8         |
| 12        3         9         | 5         8         12        | 6         7         4         |
:-------------------------------+-------------------------------+-------------------------------:
| 459      1         *24        | 29       *45       3         | 8         6         7         |
| -25        7         3         | 6         *25        8         | 4         1         9         |
| 49        8         6         | 7         1         49        | 5         2         3         |
:-------------------------------+-------------------------------+-------------------------------:
| 7         6         5         | 3         24        24        | 9         8         1         |
| 48        9         48        | 1         6         7         | 3         5         2         |
| 3         2         1         | 8         9         5         | 7         4         6         |
'-------------------------------.-------------------------------.-------------------------------'


Singles from then on.
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enxio27
PostPosted: Tue Jul 01, 2008 3:19 pm 
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JLynn wrote:
Two steps, an X-Wing and an XY-wing:


Thanks, JLynn!

Well, I'm very proud of myself! :dance: :bouncy: I managed to finish the puzzle without peeking at your hidden hints, just based on your statement above.

For some reason I have never before thought to look for X-wings in which each instance of X is in a different box. I don't know why; it had just never occurred to me.

I did have to learn the XY-wing technique. I've never done those before, so I went to a tutorial and studied it. It took me a while to work out the logic, but then I found a slightly different XY-wing from the one you proposed:

2,5 r5c1; 2,4 r4c3; 4,5 r4c5

This technique is still going to take me some practice before I'm confident using it, but it may just help me crack some of the puzzles in my "unsolved" pile.

The upper left grid of the puzzle is stupidly easy (leaving only four cells unsolved without the center grid), and the other three grids aren't much more difficult, so the fact that this grid required me to learn a new technique is rather surprising to me.
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Børge
PostPosted: Tue Jul 01, 2008 8:28 pm 
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enxio27 wrote:
I did have to learn the XY-wing technique. I've never done those before, so I went to a tutorial and studied it. It took me a while to work out the logic, but then I found a slightly different XY-wing from the one you proposed:
This technique is still going to take me some practice before I'm confident using it, but it may just help me crack some of the puzzles in my "unsolved" pile.
When you are at it, learn XYZ-Wing also.

enxio27 wrote:
The upper left grid of the puzzle is stupidly easy (leaving only four cells unsolved without the center grid), and the other three grids aren't much more difficult, so the fact that this grid required me to learn a new technique is rather surprising to me.
Hope you are not referring to a puzzle, which I have created. :pallid:
From the code it does not look so. 8-)

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enxio27
PostPosted: Tue Jul 01, 2008 10:12 pm 
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Børge wrote:
When you are at it, learn XYZ-Wing also.

I'll take a look at it.

Quote:
Hope you are not referring to a puzzle, which I have created. :pallid:
From the code it does not look so. 8-)

No, this is one from sudoku.binaryworlds.com. I got stuck on the enxio27 Samurai #1 (I'm thinking I must have made a mistake somewhere), and this other one just happened to be the next one in the stack.
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