The New Sudoku Players' Forum

[sususudoku]

Help, friends!

29 8 4 579 1579 157 3 6 27
6 7 5 48 2 3 18 148 9
239 1 39 4789 789 6 78 248 5

4 569 69 3 5678 578 2 189 178
8 3 2 1 67 9 67 5 4
7 569 1 2 568 4 689 89 3

1 4 379 6 3789 278 5 289 28
5 69 679 789 4 278 189 3 128
39 2 8 59 1359 15 4 7 6

Haven't yet learned X-wings or Y-wings or strong links -- but dyin' to find a place where I can learn them!

Thanks...JT

[udosuk]

Your puzzle needs a couple advanced techniques to solve.

First, there is an xy-wing (click this link if you want to learn more):

Code: Select all

 *-----------------------------------------------------------*
 | 29    8     4     | 579   1579  157   | 3     6    *27    |
 | 6     7     5     | 48    2     3     | 18    148   9     |
 | 239   1     39    | 4789  789   6     |*78    248   5     |
 |-------------------+-------------------+-------------------|
 | 4     569   69    | 3     5678  578   | 2     189   178   |
 | 8     3     2     | 1     67    9     | 67    5     4     |
 | 7     569   1     | 2     568   4     | 689   89    3     |
 |-------------------+-------------------+-------------------|
 | 1     4     379   | 6     3789  278   | 5     289  *28    |
 | 5     69    679   | 789   4     278   |-189   3     128   |
 | 39    2     8     | 59    1359  15    | 4     7     6     |
 *-----------------------------------------------------------*

r1c9=2 or 7
=> either r3c7=8 or r7c9=8 or both
=> r8c7 cannot be 8

Next, there is an ALS-xz (click this link if you want to learn more):

Code: Select all

 *-----------------------------------------------------------*
 | 29    8     4     | 579   1579  157   | 3     6     27    |
 | 6     7     5     |-48    2     3     |A18    148   9     |
 | 239   1     39    | 4789  789   6     | 78    248   5     |
 |-------------------+-------------------+-------------------|
 | 4     569   69    | 3     5678  578   | 2     189   178   |
 | 8     3     2     | 1     67    9     | 67    5     4     |
 | 7     569   1     | 2     568   4     | 689   89    3     |
 |-------------------+-------------------+-------------------|
 | 1     4     379   | 6     3789  278   | 5     289   28    |
 | 5    B69   B679   |B789   4     278   |B19    3     128   |
 | 39    2     8     | 59    1359  15    | 4     7     6     |
 *-----------------------------------------------------------*

ALS A: r2c7={18}
ALS B: r8c2347={16789}
restricted common: x=1
common: z=8

Therefore r2c4 cannot be 8.

Logical reasoning:
r2c7 and r8c7 cannot both be 1.
If r2c7<>1, r2c7=8 => r2c4<>8
If r8c7<>1, r8c7=9 => r8c2=6 => r8c3=7 => r8c4=8 => r2c4<>8
So either way, r2c4 cannot be 8.

Hence, r2c4=4 and singles solve the rest.

This post is a very comprehensive and useful directory for you to learn most techniques.

[sususudoku]

Gonna study that one real hard. Time I advanced to the next level.

Thanks again, udo(n't)suk

[hrcjcr]

udosuk,
Thank you for the research and references However, the puzzle above is a better example of the ALS xz.
In benny's example from the link (below), I think a cleaner tactic would be to use an xyz wing on r6c16 & r5c1 x=1, which eliminates 1 from r6c3.

+-------------+-------------+-------------+
| 24 7 8 | 24 6 5 | 1 9 3 |
| 9 3 24 | 248 1 48 | 56 7 56 |
| 5 1 6 | 7 3 9 | 8 4 2 |
+-------------+-------------+-------------+
| 28 9 23 | 458 7 6 |#35 1 #45 |
|*17 6 5 | 3 9 14 | 2 8 #47 |
| 178 4 *13 | 58 2 18 | 357 6 9 |
+-------------+-------------+-------------+
| 6 5 7 | 1 4 2 | 9 3 8 |
| 14 2 14 | 9 8 3 | 67 5 67 |
| 3 8 9 | 6 5 7 | 4 2 1 |
+-------------+-------------+-------------+
* and # are from his original post on the ALS xz.

[udosuk]

hrcjcr, good observation that the XYZ-wing can replace the ALS-xz in bennys' example, but his example was just a demonstration of the ALS technique and as long as it's applied correctly in valid logic I don't see too much a problem there.

Just a little note to you guys: to post the grids neatly (with the multiple spaces) you need to make use of the code tags. The correct format is:

[code]
 +-------------+-------------+-------------+
 | 24  7   8   | 24  6   5   | 1   9   3   |
 | 9   3   24  | 248 1   48  | 56  7   56  |
 | 5   1   6   | 7   3   9   | 8   4   2   |
 +-------------+-------------+-------------+
 | 28  9   23  | 458 7   6   |#35  1  #45  |
 |*17  6   5   | 3   9   14  | 2   8  #47  |
 | 178 4  *13  | 58  2   18  | 357 6   9   |
 +-------------+-------------+-------------+
 | 6   5   7   | 1   4   2   | 9   3   8   |
 | 14  2   14  | 9   8   3   | 67  5   67  |
 | 3   8   9   | 6   5   7   | 4   2   1   |
 +-------------+-------------+-------------+
[/code]

The correct result should be like this:

Code: Select all

 +-------------+-------------+-------------+
 | 24  7   8   | 24  6   5   | 1   9   3   |
 | 9   3   24  | 248 1   48  | 56  7   56  |
 | 5   1   6   | 7   3   9   | 8   4   2   |
 +-------------+-------------+-------------+
 | 28  9   23  | 458 7   6   |#35  1  #45  |
 |*17  6   5   | 3   9   14  | 2   8  #47  |
 | 178 4  *13  | 58  2   18  | 357 6   9   |
 +-------------+-------------+-------------+
 | 6   5   7   | 1   4   2   | 9   3   8   |
 | 14  2   14  | 9   8   3   | 67  5   67  |
 | 3   8   9   | 6   5   7   | 4   2   1   |
 +-------------+-------------+-------------+


[ravel]

Code: Select all

 *-----------------------------------------------------------*
 | 29    8     4     | 579   1579  157   | 3     6     27    |
 | 6     7     5     | 48    2     3     | 18    148   9     |
 | 239   1     39    | 4789  789   6     | 78    248   5     |
 |-------------------+-------------------+-------------------|
 | 4     569   69    | 3     5678  578   | 2    A189  -178   |
 | 8     3     2     | 1     67    9     | 67    5     4     |
 | 7     569   1     | 2     568   4     | 689  A89    3     |
 |-------------------+-------------------+-------------------|
 | 1     4     379   | 6     3789  278   | 5    A289  B28    |
 | 5     69    679   | 789   4     278   | 19    3    B128   |
 | 39    2     8     | 59    1359  15    | 4     7     6     |
 *-----------------------------------------------------------*


For your practice, here is another ALS in the same grid, that solves the puzzle:
A 1 in r4c9 locks 2 in A to r7c8 and 2 in B to r78c9.

[hrcjcr]

[b]udosuk[/b] wrote

Just a little note to you guys: to post the grids neatly (with the multiple spaces) you need to make use of the code tags. The correct format is:
[quote][[b][/b]code]
 +-------------+-------------+-------------+
 | 24  7   8   | 24  6   5   | 1   9   3   |
 | 9   3   24  | 248 1   48  | 56  7   56  |
 | 5   1   6   | 7   3   9   | 8   4   2   |
 +-------------+-------------+-------------+
 | 28  9   23  | 458 7   6   |#35  1  #45  |
 |*17  6   5   | 3   9   14  | 2   8  #47  |
 | 178 4  *13  | 58  2   18  | 357 6   9   |
 +-------------+-------------+-------------+
 | 6   5   7   | 1   4   2   | 9   3   8   |
 | 14  2   14  | 9   8   3   | 67  5   67  |
 | 3   8   9   | 6   5   7   | 4   2   1   |
 +-------------+-------------+-------------+
[/code][/quote]
The correct result should be like this:
[code]
+-------------+-------------+-------------+
| 24 7 8 | 24 6 5 | 1 9 3 |
| 9 3 24 | 248 1 48 | 56 7 56 |
| 5 1 6 | 7 3 9 | 8 4 2 |
+-------------+-------------+-------------+
| 28 9 23 | 458 7 6 |#35 1 #45 |
|*17 6 5 | 3 9 14 | 2 8 #47 |
| 178 4 *13 | 58 2 18 | 357 6 9 |
+-------------+-------------+-------------+
| 6 5 7 | 1 4 2 | 9 3 8 |
| 14 2 14 | 9 8 3 | 67 5 67 |
| 3 8 9 | 6 5 7 | 4 2 1 |
+-------------+-------------+-------------+
[/code]
:idea:[/quote]

Not sure why, maybe it's the program I use to generate the grid, but enclosing my grid with the 'code' notations or selecting it and clicking on the code button doesn't usually work.
I also like the neat appearance. Any recommendations on how to get there?

[hrcjcr]

As evidenced by what just happened above when I quoted udosuk, something basic must be turned off on my system.

[udosuk]

hrcjcr, there are a couple possible reasons why you can't get the code tags to work:

1. Have you (mistakenly) ticked the "Disable BBCode in this post" checkbox when you post the reply?
2. Have you (mistakenly) posted the grids as your signature instead of a normal reply?

Make sure you read the following link about how to use the BBCode:
http://forum.enjoysudoku.com/faq.php?mode=bbcode

Also, in your reply window, near the bottom left there is an Options area. Make sure you see "BBCode is ON" instead of "BBCode is OFF".

If for some reason your BBCode feature is OFF, perhaps it has something to do with your profile settings. Just click the following link to edit your profile:
http://forum.enjoysudoku.com/profile.php?mode=editprofile

Make sure you have "Always allow BBCode" enabled in your preferences.