#643, April 26 - May 2, 2025:
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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Discussion...
Post an idea here...
... by: Frans Goosens
#643
With trial and error
Combination C2=349 and I8=259
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C2=3 I8=2 Wrong, Undo calculation
All reset to initial position
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C2=3 I8=5 No solution, Fixed
Combination 2-digits cells
B4=6 Wrong, Undo calculation
B4=9 Wrong, Undo calculation
All reset to initial position
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C2=3 I8=9 Wrong, Undo calculation
All reset to initial position
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C2=4 I8=2 Wrong, Undo calculation
All reset to initial position
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C2=4 I8=5 ( A6=9 ) Solved,
Total solving time is : 98 sec.
Number of logical steps is : 12092
... by: Serban
# 643 Basics to 21
1. Number 1 n=3 e=6 N=24 Nc=21 Ns= => D9=1 basics to 42
1a. XY-Wing-349 [E47,D8] => D46 <>9 => E4=9 OR D6=8 basics to 66
1b. W-wing 58 [G3,B5] => B3 <>5 => G3=5 solve
2. C(3,4,9) D9(1,2,5,7,8,9) N=9 Nc=18 Ns=7 => C2=4 & D9=1 solve
... by: Dieter
#643 - basics: %
populated cells: 21 = 26%
strategy: try to get hidden pairs or triplets. No solver used.
combinations of A4 = (3,6,7,9) and A9 = (2,6,7,9)
5 matrices left after basic checks.
start with A4/A9 =(7/6), 58% populated: solves with A5=5
... by: Serban
# 643 Basics to 21
1. Row B n=3 e=6 Nc=24 Ns=18 => B3=9 & B5=8 solve
2. Box 4 ABC456 n=2 e=7 Nc=38 Ns=13 => A6=9 & B5=8 solve
