#694, April 18 - April 24, 2026:
The Weekly 'Unsolvable' Sudoku Puzzle
by Richard Kröger, guest compiler
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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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Changes March 2026
Due to the introduction of
Forcing Nets many Weekly Unsolvable puzzles can now
be solved. I have flagged all the Sudoku ones which are solvable. I am struggling to make any new ones so we'll
have to see if the Weekly can continue. The point of the Weekly was to provoke discussion and new ideas, so
that is progress. But my solution is unlikely to be optimal so alternatives are welcome.
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.
Share and Enjoy
Supporter Members have access to all these puzzles going back to number 1.
Discussion...
Post an idea here...
... by: Frans Goosens
#694
With trial and error
Combination B1=147 and F9=158
************************************************************
B1=1 F9=1 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=1 F9=5 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=1 F9=8 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=4 F9=1 No solution, Fixed
Combination 2-digits cells
A3=1 No solution, Undo calculation
A3=8 Wrong, Undo calculation
A3=1 No solution, Fixed
B3=3 Wrong, Undo calculation
B3=9 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=4 F9=5 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=4 F9=8 No solution, Fixed
Combination 2-digits cells
A7=3 No solution, Undo calculation
A7=4 No solution, Undo calculation
C4=1 Wrong, Undo calculation
C4=8 No solution, Fixed
C5=1 Wrong, Undo calculation
C5=3 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=7 F9=1 ( B6=1 ) Solved,
Total solving time is : 150 sec.
Number of logical steps is : 41069
... by: Serban
# 694 J4=1 Basics 26
1. G7=3 & H7=1 solve
2. G7=3 & E7=4 solve
3. G7=3 & J7=8 solve
4. E2=9 & D4=3 solve
5. A2=8 & B4=7 solve
... by: Andrew Stuart
I want to apologise again for Unsolvables #691 and #692. The MinLex of these puzzles showed they were essentially the same as #690. Some weeks ago I mentioned in passing to another compiler I was struggling to make Weekly unsolvables given the recent upgrades and he volunteered a set. I chose the first three from the top of his list but it wasn't stated at the time "those groups were a shuffle of one puzzle so you could find one you liked". Instead I picked the top three. Some bad comms there, apologies. I’ve swapped out #693 for other reasons this morning at 8am.
