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VH+ 090521

 
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immpy



Joined: 06 May 2017
Posts: 455

PostPosted: Sun Sep 05, 2021 4:15 pm    Post subject: VH+ 090521 Reply with quote

Hello all, enjoy the puzzle...

Code:

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

Play this puzzle online at the Daily Sudoku site

cheers...immp
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Clement



Joined: 24 Apr 2006
Posts: 1057
Location: Dar es Salaam Tanzania

PostPosted: Sun Sep 05, 2021 7:40 pm    Post subject: VH+090521 Reply with quote

Code:

+-----------------------+-------------------+------------------+
|f249       49      3   | 6      g2-4     5 | 7     8       1  |
| 6         5       7   | 8       9       1 | 4     3       2  |
| 8         1       24  | 24      3       7 | 9     5       6  |
+-----------------------+-------------------+------------------+
| 2459     b469     245 | 7      c16      3 | 8     c12      45|
| 47        3       1   | 25      25      8 | 6      9       47|
|e257      b67      8   | 9       16      4 | 3     d12      57|
+-----------------------+-------------------+------------------+
| 3         2       45  | 45      8       6 | 1      7       9 |
| 1        b47      9   | 3      a47      2 | 5      6       8 |
| 57        8       6   | 1       57      9 | 2      4       3 |
+-----------------------+-------------------+------------------+

(4)r8c5 = (476)r864c2 - (6=2)r4c58 - r6c8 = r6c1 - r1c1 = (2)r1c5 => - 4r1c5; stte
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TomC



Joined: 30 Oct 2020
Posts: 109
Location: Wales

PostPosted: Mon Sep 06, 2021 5:48 am    Post subject: Reply with quote

Code:

+--------------+---------+---------+
| 249  49  3   | 6  24 5 | 7 8  1  |
| 6    5   7   | 8  9  1 | 4 3  2  |
| 8    1   24  | 24 3  7 | 9 5  6  |
+--------------+---------+---------+
| 2459 469 245 | 7  16 3 | 8 12 45 |
| 47   3   1   | 25 25 8 | 6 9  47 |
| 257  67  8   | 9  16 4 | 3 12 57 |
+--------------+---------+---------+
| 3    2   45  | 45 8  6 | 1 7  9  |
| 1    47  9   | 3  47 2 | 5 6  8  |
| 57   8   6   | 1  57 9 | 2 4  3  |
+--------------+---------+---------+

Play this puzzle online at the Daily Sudoku site

r5c1 <>7 as then r4c9=5 and r9c1= 5 leads to no 5's in box 4
then a couple of basics reveals a 257 XY wing giving r4c1 and r7c3 <> 5
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dongrave



Joined: 06 Mar 2014
Posts: 443

PostPosted: Mon Sep 06, 2021 3:22 pm    Post subject: Reply with quote

I used the chain: 7r6c2-[(7=4*)r5c1 -(7=5)r6c9]-(57=2)r6c1-(24*=9)r1c1-(9=4)r1c2-(4=7)r8c2 contradiction => r6c2 <> 7; stte.
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Mogulmeister



Joined: 03 May 2007
Posts: 873

PostPosted: Wed Sep 08, 2021 10:29 am    Post subject: Reply with quote

This was a well designed puzzle Immp and took some tinkering with. Thank you.

Sorry about the busy diagram (below) but there is a fair bit going on.

Firstly, we have an AALS

Set A (Green) {2,4,5,7,9}
Set B (Beige) {5,7}

Restricted common is 5.

Common Candidate 7 in Red can see the 7ís in A & B and would normally be eliminated. However, the restricted common is banjaxed because there is another 5 in r4c1.

The key here is the yellow square at r4c9 <45>.

If it is 5 then we remove that pesky 5 in r4c1. The ALS XZ now solves the puzzle. R6c2 <> 7.

-OR-

If it is 4 then
(5=4)r4c9-(4=25)r4c3

and at the same time:

(5=4)r4c9=(5)r6c9-(5=27)r6c1

Which forms Tom's previously mentioned <257> XY wing (purple+r6c1) and r4c1 and r7c3 <> 5.

Either route solves. For the sake of completeness the XY wing also removes the 7 (red).


Last edited by Mogulmeister on Tue Oct 19, 2021 10:01 am; edited 11 times in total
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Mogulmeister



Joined: 03 May 2007
Posts: 873

PostPosted: Wed Sep 08, 2021 10:33 am    Post subject: Reply with quote

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Mogulmeister



Joined: 03 May 2007
Posts: 873

PostPosted: Wed Sep 08, 2021 11:23 am    Post subject: Reply with quote

Of course there is a snappier solution but I do like ALS solves !

You can simplify matters by saying that:

If yellow square is 4 then <257> XY Wing in solves

otherwise

If yellow square is 5 then r6c9 = 7 so r6c2 <> 7 solves
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