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VHplus 2011 09 17

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arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Sat Sep 17, 2011 4:22 pm Post subject: VHplus 2011 09 17

a VH+ with a nice one stepper

Code:

*-----------*
|5..|26.|.1.|
|7..|8..|65.|
|.1.|9..|...|
|---+---+---|
|..7|.5.|9.8|
|...|3.7|...|
|1.3|.8.|5..|
|---+---+---|
|...|..9|.8.|
|.64|..8|..5|
|.5.|.26|..7|
*-----------*

keith

Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

Posted: Sat Sep 17, 2011 6:36 pm Post subject:

After basics:

Code:

+----------------+----------------+----------------+
| 5 348 89 | 2 6 34 | 7 1 49e |
| 7 234 29 | 8 14 134 | 6 5 249e |
| 24 1 6 | 9 7 5 | 8 24f 3 |
+----------------+----------------+----------------+
| 6 24 7 | 14b 5 124 | 9 3 8 |
| 248 248 5 | 3 9 7 | 24 6 1 |
| 1 9 3 | 6 8 24c | 5 7 24d |
+----------------+----------------+----------------+
| 23 7 12 | 5 134 9 | 1234 8 6 |
| 239 6 4 | 7 13 8 | 123 29 5 |
| 389 5 18 | 14a 2 6 | 134 -49 7 |
+----------------+----------------+----------------+

There are plenty of backdoor cells that, if solved here, would make a one-stepper.

The most plausible one I can see is: abcd is a kite / skyscraper on 4. Extend d to f with grouped coloring, solving R9C8.

abcdf are all backdoor cells, and there are others. Any move that solves one of them is a one-stepper.

Keith

arkietech

Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

Posted: Sat Sep 17, 2011 7:00 pm Post subject:

Code:

*-----------------------------------------------------------*
| 5 348 89 | 2 6 34 | 7 1 49 |
| 7 234 29 | 8 14 134 | 6 5 (2)49 |
| 24 1 6 | 9 7 5 | 8 f24 3 |
|-------------------+-------------------+-------------------|
| 6 24 7 |c14 5 124 | 9 3 8 |
| 248 248 5 | 3 9 7 | 24 6 1 |
| 1 9 3 | 6 8 b24 | 5 7 a24 |
|-------------------+-------------------+-------------------|
| 23 7 12 | 5 134 9 | 1234 8 6 |
| 239 6 4 | 7 13 8 | 123 29 5 |
| 389 5 18 |d14 2 6 | 134 e49 7 |
*-----------------------------------------------------------*
(2)r2c9=(2-4)r6c9=(4)r6c6-(4)r4c4=(4)r9c4-(4)r9c8=(4-2)r3c8=(2)r2c9 => r2c9=2

A trick I often use is to find a point where two strong links meet eg (2)r2c9 then see if i can connect the two endpoints (a and f) forming a Discontinuous Nice Loop discontinous at the point the strong links meet (r2c9) and allowing me to set the digit. In this case r2c9=2.

another example:
*-----------------------------------------------------------*
| 5 g348 f89 | 2 6 34 | 7 1 49 |
| 7 (3)24 29 | 8 134 a134 | 6 5 249 |
| 24 1 6 | 9 7 5 | 8 24 3 |
|-------------------+-------------------+-------------------|
| 6 24 7 |c14 5 b124 | 9 3 8 |
| 248 248 5 | 3 9 7 | 24 6 1 |
| 1 9 3 | 6 8 24 | 5 7 24 |
|-------------------+-------------------+-------------------|
| 23 7 12 | 5 134 9 | 1234 8 6 |
| 239 6 4 | 7 13 8 | 123 29 5 |
| 389 5 e18 |d14 2 6 | 134 49 7 |
*-----------------------------------------------------------*
(3)r2c2=(3-1)r2c6=(1)r4c6-(1)r4c4=(1)r9c4-(1=8)r9c3-(8)r1c3=(8-3)r1c2=(3)r2c2 => r2c2=3

sadly this one does not break or solve the puzzle like the first one did.

There are several other examples in this position of the puzzle.

r5c2=8
r8c1=9
r9c1=8

I did not run them out.

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