#673, November 22 - November 28, 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: Serban
# 673 D7=4 E8=6 F9=7 Basics to 27
1. Number 3 n=2 e=7 N=24 Nc=16 Ns=16 => G7=3 solve
1. Column 7 n=4 e=5 Nc=10 Ns=9 => G7=3 solve
2. Number 4 n=3 e=6 N=17 Nc=9 Ns=9 => H1=4 solve
Note:A2=B4=C8=4
3.Column 8 n=4 e=5 Nc=13 Ns=2 => A8=5 & H8=1 solve
4.Column 9 n=3 e=6 Nc=27 Ns=27 => B9=1 & H9=9 solve
... by: BGH
Ops!
Goosen found A3/F4 First!
I found it independently.
... by: BGH
Basic Deterministics 33.3
2 Step Solution
3 @ A3 48.1% Cell Pair
3 @ F4 Solution Cell Pair
... by: Frans Goosens
#673
Combination 2-digits cells
A3=3 ( F4=3 ) Solved,
Total solving time is : 12 sec.
Number of logical steps is : 1056
... by: Dieter
#673 - initially populated cells: 24 = 29,6%
No solver used, solver = brain.
basics: D7=4, E8=6, F9=7
populated cells: 27 = 33,3%
Strategy: Numbers 7,4,9,2,6 occur most frequently, combine two cells.
combinations of A4 = (4,7,9) and F1 = (2,5,6)
2 matrices left after basic checks: A4/F1 = 7/2 and 9/5
A4/F1 = 7/2 solves with F4=3
Optimization:
F1=2 & F4=3 solve.
