#696, May 2 - May 8, 2026:
The Weekly 'Unsolvable' Sudoku Puzzle
by Richard Kröger, guest compiler
|
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).
|
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
#696
With trial and error
Combination B1=139 and F9=245
************************************************************
B1=1 F9=2 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=1 F9=4 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=1 F9=5 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=3 F9=2 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=3 F9=4 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=3 F9=5 Wrong, Undo calculation
All reset to initial position
************************************************************
B1=9 F9=2 No solution, Fixed
Combination 2-digits cells
B4=1 Wrong, Undo calculation
B4=8 No solution, Fixed
B5=1 Wrong, Undo calculation
B5=5 ( A8=5 ) Solved,
Total solving time is : 268 sec.
Number of logical steps is : 31937
... by: Dieter
#696 - initially populated cells: 22 = 27,2 %
No solver used, solver = brain.
basics: A6=2
populated cells: 23 = 28,4 %
Strategy: numbers 2,4,7,8 occur most frequently, combine two cells with almost same candidates.
combinations of D7 = (2,3,4,5) and D9 = (2,3,4,5,7)
after basic checks 5 matrices left: D7/D9 = 5/4, 3/5, 4/5, 2/7 and 4/7
D7/D9 = 4/5 solves with H5=6
Optimization:
D7=4 & H5=6 solve.
... by: Serban
# 696 A6=2 Basics to 23
1. E2=2 & G3=3 solve
... by: Yves
E5=9 & G3=3
J5=4 & C7=6
A8=5 & F2=1
etc ...
