## Does somebody have example for sudoku, which requires ...

Advanced methods and approaches for solving Sudoku puzzles

### Does somebody have example for sudoku, which requires ...

Unique rectangle/loop type 3 with hidden quad?

I found with naked quad and I suppose it is possible to have also hidden quad if none of the cells in a group is solved.
Morgoth

Posts: 20
Joined: 06 December 2005

Here it is

Code: Select all
`000000000000200600314000000008094013060005740000003002000000800501000000400800029`

This is extremely rare pattern.
It can be easily found if a pattern with empty group is used.
Morgoth

Posts: 20
Joined: 06 December 2005

Excellent puzzle!

After SSTS gets stuck:

*-----------------------------------------------------------*
|-2678 -2579 -2679  |*34   *147  #1789  |*13   #589  *145   |
| 78    579   79    | 2     1347  1789  | 6     3589  145   |
| 3     1     4     | 5     6    #89    | 2    #89    7     |
|-------------------+-------------------+-------------------|
| 27    27    8     | 6     9     4     | 5     1     3     |
| 9     6     3     | 1     2     5     | 7     4     8     |
| 1     4     5     | 7     8     3     | 9     6     2     |
|-------------------+-------------------+-------------------|
| 267   2379  2679  | 34    147   167   | 8     57    15    |
| 5     8     1     | 9     37    2     | 4     37    6     |
| 4     37    67    | 8     5     167   | 13    2     9     |
*-----------------------------------------------------------*

UR {89} in r13c68 => r1c68 must have one of {157}
=> Hidden quad {2689} in r1c123+r1c(6|8)
(Or alternatively, naked quint {13457} in r1c4579+r1c(6|8))
=> 5 & 7 eliminated from r1c123

After that the puzzle is solved under SSTS.

Morgoth wrote:This is extremely rare pattern.
It can be easily found if a pattern with empty group is used.

If naked quad is given a higher priority than hidden quad then you can only get the latter when there is an empty row/column/block and a "naked quint" in 5 of the cells...
udosuk

Posts: 2698
Joined: 17 July 2005

udosuk wrote:Excellent puzzle!
Morgoth wrote:This is extremely rare pattern.
It can be easily found if a pattern with empty group is used.

If naked quad is given a higher priority than hidden quad then you can only get the latter when there is an empty row/column/block and a "naked quint" in 5 of the cells...

Yes, I know. My idea was that using a pattern with empty group will give you high possibility to have empty group in the end
The puzzles I was looking for this UR were without pattern, but made from the first version of my generator which was usually left the first row without hints during the minimization
Morgoth

Posts: 20
Joined: 06 December 2005