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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Mon Jan 28, 2008 12:19 am Post subject: competition #931 |
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| Code: | . . . | 7 . . | . . .
. 2 . | . 5 9 | . 7 1
8 . . | . . . | 9 . .
---------------------
. 5 . | 2 . . | . 3 7
9 . . | . . . | . . 6
7 6 . | . . 4 | . 9 .
---------------------
. . 4 | . . . | . . 3
3 8 . | 9 4 . | . 2 .
. . . | . . 7 | . . .
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http://www.sudoku.org.uk/DailySudoku.asp?day=27/01/2008
this one took me a little longer to solve. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Jan 28, 2008 10:05 am Post subject: |
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| Code: | *------------------------------------------------------*
| 15 34 9 | 7 1268 28 | 35-8 568 248 |
|*46 2 36 |#48 5 9 |@38 7 1 |
| 8 7 15 | 1346 1236 23 | 9 56 24 |
|----------------+------------------+------------------|
|&14 5 18 | 2 9 6 |*148 3 7 |
| 9 *34 1238 | 1358 7 358 |*12458 &458 6 |
| 7 6 1238 | 135 138 4 | 1258 9 28 |
|----------------+------------------+------------------|
| 256 9 4 | 568 268 258 | 7 1 3 |
| 3 8 7 | 9 4 1 | 6 2 5 |
| 256 1 56 | 356 236 7 |#48 48 9 |
*------------------------------------------------------* |
Half M-wing 48:
r9c7=4 => r45c7<>4 => r5c8=4 => r5c2<>4 => r4c1=4 => r2c1<>4 => r2c4=4
String link for 8 in row 2 r2c4-r2c7
=> r7c7 or r2c7 must be 8 => r1c7<>8
| Code: | *---------------------------------------------------*
|^15 -34 9 | 7 1268 28 |^35 568 24 |
|*46 2 *36 | 48 5 9 |-38 7 1 |
| 8 7 @15 | 1346 1236 23 | 9 56 24 |
|---------------+------------------+----------------|
|*14 5 8 | 2 9 6 |@14 3 7 |
| 9 34 #123 | 1358 7 358 |#1245 45 6 |
| 7 6 #123 | 135 13 4 |#125 9 8 |
|---------------+------------------+----------------|
| 256 9 4 | 568 268 258 | 7 1 3 |
| 3 8 7 | 9 4 1 | 6 2 5 |
| 256 1 56 | 356 236 7 | 48 48 9 |
*---------------------------------------------------* |
UR 12 in r56c37: in columns 3 and 7 only 1 can be outside the UR:
r3c3=1 => r1c1=5 => r1c7=3
r4c7=1 => r4c1=4 => r2c1=6 => r2c3=3
=> r1c2<>3, r2c7<>3 |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Mon Jan 28, 2008 8:13 pm Post subject: |
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I've been trying to grasp this "snake-lady" technique for several weeks and finally the penny dropped(SUDOKU will never be the same once you're hooked on
this Gorgon) and it seems a powerful technique to break a puzzle wide open.
Medusa colouring causes a trap in Box 2 for digit <28> in R1C5(two opposite colours in the same multivalue cell eliminates the uncoloured candidates in that
cell) and <6> in R3C4( an uncoulored digit that can see the same digit coloured and has the opposite colour in its own cell can be eliminated), so <8> in
R1C89(they can see both the 8G in R2C7 and they have the opposite colour R in their own cell), R4C7 and <25> in R1C7 are also eliminated. Start colouring
with the [56] pair in R9C3.
| Code: |
+--------------------------+--------------------------+----------------------------+
| 1G5R 4G3R 9 | 7 1R-[28]6G 28 |-[25]3G8 56R-[8] 24R-[8]|
| 4R6G 2 3G6R | 4G8R 5 9 | 3R8G 7 1 |
| 8 7 1R5G | 134R-[6] 1236 23 | 9 5R6G 2R4G |
+--------------------------+--------------------------+----------------------------+
| 1R4G 5 18 | 2 9 6 | 14R-[8] 3 7 |
| 9 4R3G 1238 | 1358 7 358 | 12458 458 6 |
| 7 6 1238 | 1358 138 4 | 1258 9 28 |
+--------------------------+--------------------------+----------------------------+
| 256 9 4 | 568 268 258 | 7 1 3 |
| 3 8 7 | 9 4 1 | 6 2 5 |
| 256 1 5R6G | 356 236 7 | 48 48 9 |
+--------------------------+--------------------------+----------------------------+ |
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