#657, August 2 - August 8, 2025:
The Weekly 'Unsolvable' Sudoku Puzzle
by Andrew Stuart
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WARNING: This is the Weekly 'Unsolvable' Sudoku, rated above 'Extreme'.
This is currently unsolvable by my solver, except perhaps with trial and error strategies.
Using the solver will not help you. (much).
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Archive
Each week a new 'unsolvable' will be published and the previous will be accessible here from this archive section.
If you like very tough puzzles, these are for you.
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Discussion...
Post an idea here...
... by: Aqua
I build a solver that can solve it. It is a bitmask-dlx solution with advanced optimisations along the way.. Pure JavaScript of course, and am gonna put WebAssembler code directly in it and worker code (for multi core batch processing) in it too.. It solves any puzzle known to man at 1ms or below at the moment. It could be worth checking that out if wanting to improve your solver! Anyways.. I can concur the puzzle is solvable. O.O
cheers!
~ Aqua
2 1 3 | 8 9 4 | 5 6 7
9 6 8 | 2 7 5 | 4 1 3
7 5 4 | 6 1 3 | 2 9 8
------+-------+------
8 3 1 | 5 2 9 | 7 4 6
5 7 9 | 3 4 6 | 1 8 2
4 2 6 | 1 8 7 | 9 3 5
------+-------+------
6 4 5 | 7 3 1 | 8 2 9
1 8 7 | 9 6 2 | 3 5 4
3 9 2 | 4 5 8 | 6 7 1
... by: Envy E
Following previous comments
+2 C6 [ +2 H4 +9 J4 ( +9 B1 +2 A1 A2 +2 B7) +3 J1 +7 J2 +7 D3 +3+7 G7 H7 +8 H9 +6 H3 +6 E6 +3 E6 -2 E6 ]
With B6 set to 5 C6 set to 3 and E6 set to 6 puzzle is rated 429 Extreme
... by: Envy E
Previous comment eliminates 4 from A4 A8 A9 B6 C6 E6
+5 B3 ( +5 G1 +2+8 E1 ) +2 B6 (+4 A6 +2+8 A1 ) +2 H4 +9 J4 +3 J1 +9 B1 +4+6 D1 F1 +5 F3 -5 B3
B6 set to 5
... by: Envy E
-4+2 A6 +2 H4 +9 J4 [ +9 B1 +2 C2 ( +5 B3 C3 ) +2 B7 ] +3 J1 +7 J2 +7 D3 +3+7 G7 H7 +8 H9 +6 H3
+4 H6 +4 F3 +4 A1
... by: Dieter
#657 - initially populated cells: 23 = 28,4%
No solver used.
basics: F4=1, D6=9
populated cells: 25 = 30,9%
Strategy: Find cell which has big impact on rows and columns
D7 = (3,4,7,8)
D7 = 7 solves.
... by: Frans Goosens
#657
Combinetion 2-digits cells
A6=2 Wrong, Undo calculation
A6=4 ( E4=3 ) Solved,
Total solving time is : 32 sec.
Number of logical steps is : 1705
... by: Dieter
#657 - initially populated cells: 23 = 28,4%
No solver used.
basics: F4=1, D6=9
populated cells: 25 = 30,9%
Strategy: Numbers 1,5,9,2,6 occur most frequently, combine two cells
combinations of C2 = (1,2,5,8,9) and C6 = (2,3,4,5)
2 matrices remain after basic checks: (C2/C6) = (2/3) and (5/3)
(C2/C6) =(5/3) solves with J4=4
Review:
J4=4 solves
... by: Yves
A9=7 E1=5 E9=2 Solve
... by: Serban
# 657 D6=9 F4=1 Basics to 25
1. Number 3 E4=3 solve
2. Number 7 G4=7 solve
... by: Serban
# 657 D6=9 F4=1 Basics to 25
1. Number 1 B8=1 solve
2. Number 2 B4=2 solve
3. Number 4 E5=4 OR J4=4 solve
4. Number 5 E1=5 solve
5. Number 9 [C8=9 & J2=9] OR [C8 & H4=9] solve
