... by: Serban
# 678 A6=2 A8=7 C4=6 C9=4 basics 281. Number 3 n=2 e=7 N=26 Nc=45 Ns=4 => A1=H7=3 solve
2. Number 6 n=3 e=6 N=25 Nc=30 Ns=15 => A2=6 solve
3. Number 9 n=2 e=7 N=29 Nc=59 Ns=54 => A5=9 solve
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#678, December 27 - January 2, 2026:
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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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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
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Discussion...
Post an idea here...Sunday 28-Dec-2025
1. Number 3 n=2 e=7 N=26 Nc=45 Ns=4 => A1=H7=3 solve
2. Number 6 n=3 e=6 N=25 Nc=30 Ns=15 => A2=6 solve
3. Number 9 n=2 e=7 N=29 Nc=59 Ns=54 => A5=9 solve
Saturday 27-Dec-2025
... by: Dieter
#678 - initially populated cells: 24 = 29,6 %No solver used, solver = brain.
basics: A6=2; C9=4; C4=6; A8=7
populated cells: 28 = 34,6 %
Strategy: numbers 2,7,4 occur most frequently, combine two cells.
combinations of G1 = (2,3,6) and G5 = (4,5,7,9)
after basic checks 3 matrices G1/G5 left: 2/7, 3/7 and 6/7 > G5=7
G1/G5 = 6/7 solves with G4=5
Optimization:
G1=6 & G4=5 solve.
Saturday 27-Dec-2025
... by: Serban
# 678 A6=2 A8=7 C4=6 C9=4 basics 281. Number 8 n=2 e=7 N=28 Nc=42 Ns=41 => J8=8 OR D7=8 solve
2. Number 5 n=2 e=7 N=27 Nc=39 Ns=23 => C6=5 OR D8=5 solve
Saturday 27-Dec-2025
... by: Serban
# 678 A6=2 A8=7 C4=6 C9=4 basics 281. Number 8 n=2 e=7 N=28 Nc=42 Ns=41 => J8=8 solve