Sudoku Players' Forum (clone)

Both are easy (at least for a computer). The first puzzle didn't require any diagonal based moves (other than singles). Leren

Leren wrote:Both are easy (at least for a computer). The first puzzle didn't require any diagonal based moves (other than singles). Leren

Well, all puzzles are easy for a computer. As the subject line indicates, these two are intended for dogged humans.

Mike

Leren wrote:The first puzzle didn't require any diagonal based moves (other than singles). Leren

Leren,
This one is also easy but heavily dependent on intersections:

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 . . . . . . . . .
 . . . . . . . . 1
 . . 2 . . . . . 3
 . . . . . . . . .
 . . . . . . . . .
 . 4 . 5 . . 6 . .
 . . . 4 . 7 . . .
 . . 3 . . . . . 2
 . . 1 . . . . . 8   

Regards,

Mike

Another X-sudoku for the human solver:

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 . . . . . . . 1 2
 . . . . . 3 . . .
 . . 4 . 5 1 . . .
 . . 3 . . . 6 . .
 6 . . . . . . . 1
 . . 2 . . . 7 . .
 . . . 6 8 . 9 . .
 . . . 7 . . . . .
 8 9 . . . . . . .

.......12.....3.....4.51.....3...6..6.......1..2...7.....68.9.....7.....89.......   

Mike

Code: Select all

*----------------------------------------------------*
|d35    35    89   | 49  6   7    | 48  1      2     |
| 79    1     6789 | 49  2   3    | 458 469    45679 |
| 279   267   4    | 8   5   1    | 3   679    679   |
|------------------+--------------+------------------|
| 14579 4578  3    | 2   149 49   | 6   45     4589  |
| 6     45    59   | 3   7   8    | 245 2459   1     |
| 149   48    2    | 5   149 6    | 7   349    3489  |
|------------------+--------------+------------------|
| 23457 23457 1    | 6   8   245  | 9   23457  3457  |
| 245-3 46    56   | 7  a349 2459 | 1   8      3456  |
| 8     9     67   | 1  b34  245  | 245 67    c35    |
*----------------------------------------------------*

Example of a diagonal based "Skyscraper" (3) r8c5 = r9c5 - r9c9 = (3) r1c1 => - 3 r8c1.

<edit> Fixed Typo - Thanks Hajime

Leren

Leren wrote:Example of a diagonal based "Skyscraper" (3)r8c5 = r9c5 - r9c9 = (3) r1c1 => - 3 r9c1.

A Skyscraper or X-chain of length 4 cells requires that r9c1 must 'see' r8c5 and r1c1 both, isn't ?

Code: Select all

  . . 1 . 9 . 3 . .   
  . . . . 5 . . . .   
  . . . 1 4 6 . . .   
  . . 8 . . . 2 . .   
  2 . . 5 1 9 . . 6   
  . . 9 . . . 5 . .   
  . . . 3 6 1 . . .   
  . . . . 8 . . . .   
  . . 4 . 2 . 7 . .   


After basics:

Code: Select all

+-------------------+------------+--------------------+   
| 4578   24568   1  | 278  9   28|  3   245678   2578 |   
| 4689   24789   26 | 278  5   3 | 16   26789   124789|   
| 3589   23589  2357|  1   4   6 | 89   25789   25789 |   
+-------------------+------------+--------------------+   
| 1357   1357    8  |  6   37  4 |  2    1379    1379 |   
|   2     347    37 |  5   1   9 | 48    3478     6   |   
| 13467  13467   9  | 28   37  28|  5    1347    1347 |   
+-------------------+------------+--------------------+   
| 5789   25789  257 |  3   6   1 | 489  24589   24589 |   
| 1569   23569  256 |  4   8   7 | 16    2359   12359 |   
|  368    168    4  |  9   2   5 |  7    1368     38  |   
+-------------------+------------+--------------------+   


This one needs some more X-chains of length 4, like SkyScraper,Turbot-crane,2-String-Kite and diagonal variants

<edit> maybe indeed 6 of them are too much for a "dogged human solver"
Here is a possible solution path with naked/hidden pairs/triples, pointing&claiming and those 6 X-chains

Code: Select all

*-------------------------------------------*
| 57    4    1   | 27  9   28 | 3 6    2578 |
| 9-8  *289  6   |*278 5   3  | 1 27   4    |
| 3     258  257 | 1   4   6  | 9 2578 2578 |
|----------------+------------+-------------|
| 15    15   8   | 6   37  4  | 2 379  79   |
| 2     7    3   | 5   1   9  | 8 4    6    |
| 4     6    9   |*28  37 *28 | 5 137  17   |
|----------------+------------+-------------|
| 5789  2589 257 | 3   6   1  | 4 2589 289  |
| 159   3    25  | 4   8   7  | 6 259  1259 |
| 6     18   4   | 9   2   5  | 7 18   3    |
*-------------------------------------------*

Interesting example of a Column/Main Diagonal X Wing.

Leren

Here's one wih the clues arranged symmetrically on 3 rows only:

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 . 1 2 3 . 4 5 6 .
 . . . . . . . . .
 . . . . . . . . .
 4 5 7 . 2 . 6 1 8
 . . . . . . . . .
 . . . . . . . . .
 2 . 1 8 6 7 9 . 3
 . . . . . . . . .

..........123.456...................457.2.618..................2.18679.3.........

Mike

Code: Select all

*------------------------------------------------------*
| 3    678  4  | 12567 1789   125689 | 278 789   179   |
| 78   1    2  | 3     789    4      | 5   6     79    |
| 5    678  9  | 1267  178    1268   | 3   478   1247  |
|--------------+---------------------+-----------------|
| 16   29   38 | 467   14578 *18     | 247 3479  24579 |
| 4    5    7  | 9     2      3      | 6   1     8     |
| 16   29   38 | 17    14578 *68     | 247 3479  24579 |
|--------------+---------------------+-----------------|
| 79-8 37-8 5  | 124   1349   129    |*478 2478  6     |
| 2    4    1  | 8     6      7      | 9   5     3     |
|*789  378  6  | 245   349    259    | 1   247-8 47    |
*------------------------------------------------------*

Interesting move, a Double Diagonal Skyscraper : (8) r9c1 = r4c6 - r6c6 = (8) r7c7 => - 8 r7c12, r9c8

Leren

You might like this pretty one too:

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 . . . . 1 . . . .
 . . . . . . . . .
 . . . 2 3 4 . . .
 . 5 3 . . 6 . 7 .
 . 8 2 3 . 1 9 4 .
 . 7 . 9 . . 8 3 .
 . . . 4 8 5 . . .
 . . . . . . . . .
 . . . . 2 . . . .

....1................234....53..6.7..823.194..7.9..83....485................2....

Mike

Interesting X-sudoku.
By removing 3 or 4 cells, you also get these minimal puzzles :

Code: Select all

  . . . . 1 . . . .      . . . . 1 . . . .      . . . . 1 . . . .
  . . . . . . . . .      . . . . . . . . .      . . . . . . . . .
  . . . 2 3 4 . . .      . . . 2 3 4 . . .      . . . 2 3 4 . . .
  . 5 3 . . 6 . 7 .      . 5 . . . 6 . 7 .      . 5 . . . 6 . 7 .
  . 8 . . . 1 9 4 .      . . 2 3 . . 9 4 .      . 8 . . . 1 9 4 .
  . 7 . 9 . . 8 3 .      . 7 . 9 . . 8 3 .      . 7 . 9 . . 8 3 .
  . . . . 8 5 . . .      . . . . 8 5 . . .      . . . 4 8 5 . . .
  . . . . . . . . .      . . . . . . . . .      . . . . . . . . .
  . . . . . . . . .      . . . . 2 . . . .      . . . . 2 . . . .

....1................234....53..6.7..8...194..7.9..83.....85.....................
....1................234....5...6.7...23..94..7.9..83.....85................2....
....1................234....5...6.7..8...194..7.9..83....485................2....


phil

philvo wrote:Interesting X-sudoku.
By removing 3 or 4 cells, you also get these minimal puzzles :

phil

phil, yes, you're right, but the mnimal puzzles are rated at above SE=9, much too hard for this thread. And there's t least one that you missed:

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....1.................23....42..5.6..7...183..6.8..72....374................9....  SE=9.4

Regards,

Mike