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This is a place chosen to make available some ideas (on puzzles, patterns, etc)
that seemed unsuitable for posting in a Forum, but some people may find interesting.
For difficult puzzles, possible solutions will not be shown (only hints).
For other puzzles, the solution wil be hidden so that a serious attempt can be made
without direct access to a solution.
(hopefully this will make the puzzles more interesting for newcomers)
(Guidelines for using this site here)
(useful to look up for the meaning of some unfamiliar concept)
I propose the following tough Classic Sudoku puzzle.
(found with Sudoku Architect)
,-------------------------------------------------------------------------,
9 | 147 257 12457 | 13 6 345 | 8 137 9 |
8 | 19 56 1569 | 7 1359 8 | 2 4 13 |
7 | 1479 3 8 | 2 19 49 | 5 6 17 |
|-------------------------+-----------------------+-----------------------|
6 | 2 9 47 | 5 17 6 | 3 8 147 |
5 | 3478 678 3467 | 139 12379 239 | 1679 1579 12457 |
4 | 5 1 367 | 4 8 239 | 679 79 27 |
|-------------------------+-----------------------+-----------------------|
3 | 139 25 12359 | 6 23459 7 | 149 1359 8 |
2 | 6 4 123579 | 8 2359 2359 | 179 13579 1357 |
1 | 3789 578 3579 | 39 3459 1 | 479 2 6 |
'-------------------------------------------------------------------------'
a b c d e f g h i
I propose the following Classic Sudoku puzzle.
(found with Sudoku Architect)
,--------------------------------------------------------------------------------------,
9 | 2 345789 5679 | 357 5678 1 | 789 568 46789 |
8 | 1567 1578 1567 | 9 4 568 | 3 2 1678 |
7 | 13567 1345789 15679 | 357 5678 2 | 1789 1568 146789 |
|----------------------------+----------------------------+----------------------------|
6 | 156 15 8 | 57 567 3 | 4 9 2 |
5 | 367 2 67 | 8 9 4 | 5 136 1367 |
4 | 9 357 4 | 1 2 56 | 78 368 3678 |
|----------------------------+----------------------------+----------------------------|
3 | 4 159 159 | 2 18 7 | 6 138 1389 |
2 | 17 179 2 | 6 3 89 | 189 4 5 |
1 | 8 6 3 | 4 15 59 | 2 7 19 |
'--------------------------------------------------------------------------------------'
a b c d e f g h i
Update 1 (June 13, 2026)
Looking at the digits patterns and the weak box with cell e2, full of bivalued cells,
a good opening move involves boxes with cells e5, e8, b8, b5, eliminating (8)f8 and
giving 9 placements and basic eliminations.
,--------------------------------------------------------------------------------------,
9 | 2 345789 5679 | 357 5678 1 | 789 568 46789 |
8 | 1567 1578 1567 | 9 4 56-8 | 3 2 1678 |
7 | 13567 1345789 15679 | 357 5678 2 | 1789 1568 146789 |
|----------------------------+----------------------------+----------------------------|
6 | 156 15 8 | 57 567 3 | 4 9 2 |
5 | 367 2 67 | 8 9 4 | 5 136 1367 |
4 | 9 357 4 | 1 2 56 | 78 368 3678 |
|----------------------------+----------------------------+----------------------------|
3 | 4 159 159 | 2 18 7 | 6 138 1389 |
2 | 17 179 2 | 6 3 89 | 189 4 5 |
1 | 8 6 3 | 4 15 59 | 2 7 19 |
'--------------------------------------------------------------------------------------'
a b c d e f g h i
Final update (June 14, 2026)
After step 1, one gets
,----------------------------------------------------------------,
9 | 2 345789 5679 | 357 678 1 | 78 568 49 |
8 | 567 578 1 | 9 4 56 | 3 2 678 |
7 | 3567 345789 5679 | 357 678 2 | 1 568 49 |
|-------------------------+--------------------+-----------------|
6 | 156 15 8 | 57 67 3 | 4 9 2 |
5 | 367 2 67 | 8 9 4 | 5 1 367 |
4 | 9 357 4 | 1 2 56 | 78 368 3678 |
|-------------------------+--------------------+-----------------|
3 | 4 59 59 | 2 1 7 | 6 38 38 |
2 | 17 17 2 | 6 3 8 | 9 4 5 |
1 | 8 6 3 | 4 5 9 | 2 7 1 |
'----------------------------------------------------------------'
a b c d e f g h i
Now there are many easy ways to solve the puzzle using a few single
digit patterns.
EDIT: e.g., pattern of 6 (get -6 a8, -6 i8), basics,
and pattern of 7.
Created: February 12, 2024
Contact: sudo.jco.br@gmail.com